Does Letus Extreme lose more light than Brevis

[Cinemano]

I wondered if the Letus extreem loses more light and detail than then Brevis. Seing as it has a prism to flip the image right side up and the brevis kinda goes directly to the lens then yu flip it in post..

[Barry_Green]

There are many tests here on the forum. Unfortunately, some of them conflict with others, so an absolute answer is difficult to find with certainty. However, I'd feel confident saying that they lose approximately the same amount of light and deliver approximately the same sharpness.

[jbednarski]

I've owned both and would agree with Barry that they both lose about a half stop of light. The hands down winner in sharpness is the Letus EX though.

[Kholi]

And the Letus is Flipped and loses that much light. Add a flip to the Brevis and that changes thing.

[jbednarski]

That is true. I owned the "pre-flip" system and it lost .5 stops and just wasn't very sharp. Add the flip module and who knows.

[Matty_g]

With the brevis stopping down one stop on the 35mm lens does not always equal one stop.
How is the letus with that?

[Kholi]

It's pretty spot on with my lenses. The F1.4 50mm Nikon, going from 1.4 to 2 doesn't see anything but a change in the Bokeh Rendition. 2 to 2.8 responds accordingly. Edit: You're supposed to come out and mess with the LetusEX! Stop writing and get o'er here. =P

Jbed -- The Brevis + Flip looks to be a lot sharper than the Brevis alone. Makes for a good reason to buy the flip unit ASAP.

[Lenilenapi]

Well the more you read the more you'll see people have different experience with these adapters. I wish I could explain why.

In my tests a Pre-Flip Brevis with the CF1L diffuser was definitely faster than the Letus or the SGPro Rev 2 (also pre flip). However it was different with the 35mm lens at f1.4 or f2.8.

The Pre-flip Brevis saw no change in Boken or exposure from 35mm 2.8 to 1.4. It just didn't seem to see that light. The other adapters saw a gain as we opened to f1.4 though less than 2 stops. Thus in my tests the Brevis was only slightly faster than the others at f1.4 , but nearly a full stop faster at 2.8 and beyond.

Matty g is right about the Brevis not being linear with respect to light loss. I didn't find any of them to be, but some people say the SG and the Letus are.

Don't know how the flip changes this. I didn't see any significant sharpness difference between the Letus & Brevis but others have.

Note in my tests the Letus is the slowest which surprised me - keep in mind though that others have found the Letus to be faster than the SG so your mileage may vary.


with an 85mm/f1.4 Nikkor on my HVX:

@ f1.4 Brevis lost about .5 stop
SGPro .6 stop
Letus Ex 1 stop (if you corrected for the extra zoom-in due to being offset it was maybe .85)

f2.8 Brevis .5 stop
SGPro 1.2 stops
Letus Ex 1.6 stops

Lenny Levy

[Dennis Wood]

Lenny, you have no idea how refreshing your approach (based on real testing) is to us :-)

All of the demo footage (http://www.cinevate.com/website/index.php/demo/) currently featured on our website was shot on non-flipped Brevis units, and you won't hear much in the of complaints regarding sharpness! You'll start to see many reviews as folks get and use their flip modules this week...but Paul Nordin had some very positive first comments. (http://www.cinevate.com/phpBB2/viewtopic.php?p=12781#12781) You will see an in-depth technical review of the flip system with charts etc. published likely this week.

The Brevis with CF1Le or CF1 (flipped or not) was shown to be as much as 3-5 stops more efficient than the M2 and SGpro shooting at F8 in Phil Bloom's review last year. So there is a big difference in the adapters as you stop down. I do end up shooting at f4 to f5.6 a lot, and the fact that we can stop down a lens to it's sweet spot while losing only a stop or two of light is very, very cool.

[Kholi]

Last weekend I shot some pickups for a feature I DPed late last year. We shot with two HVX200s both with Brevis, PL, and Zeiss Superspeed cinema lenses. I was lucky enough to test out the flip module on the B-Camera and can say unequivocally, that it rocks. The image was noticeably sharper on the edges with less chromatic aberration. In a couple of configurations I had both cams setup in opposite over the shoulder angles for dialog coverage, so there are some good apples-to-apples comparisons of the flipped and non-flipped images.

From that same linked first user comment. And it further goes on to talk about using spacers. Part of the reason you can't use those Canon k-35 lenses on the M2 and Brevis is because the GG is too close. You can use them on the SGpro just fine.

Sorry, but that First user comment pretty much mirrors what I said: The Brevis' image sharpness increases with the flip unit attached.

[Dennis Wood]

There's no question that the Brevis flip/optics improves our image quality because that was the goal of a year's worth of development :-) However, there are plenty of folks out there who have done truly amazing work with the non-flipped unit (again, referring to the demo clips). It's true that our flipped configuration is more flexible with regard to framing 16x22 format lenses like the ones Paul is referring to. Cinema lenses have always been fully supported on our PL and OCT 19 mounts, but some camera/lens combinations required using a $20 spacer between the unit and our 72mm achromat. Given the number of PL/OCT19 mounts we've provided to our customers, suggesting that cinema format lenses cannot be used with the non-flipped Brevis is incorrect. In fact, Paul has been shooting PL mount cinema lenses almost exclusively for the last year.

In any case, I think most will agree that the flipped image, increase in edge sharpness, and reduction in CA balances nicely with the extra weight and .2 stops or so of light loss :-) Lenny's observation that at f2.8 the system is a stop faster than the units tested bodes well for folks using slower wide angle primes and zoom lenses.

[Kholi]

There's no question that the Brevis flip/optics improves our image quality because that was the goal of a year's worth of development :-) However, there are plenty of folks out there who have done truly amazing work with the non-flipped unit (again, referring to the demo clips).

How does the flip improve the edge-to-edge sharpness? Is it because of the space between the ground glass or achromat to the camera? Could a user extend the space and achieve better edge-to-edge sharpness with the Brevis?

Adding extra glass shouldn't improve sharpness, it's another layer for light to travel through. However, the space could/would, am I wrong?


It's true that our flipped configuration is more flexible with regard to framing 16x22 format lenses like the ones Paul is referring to. Cinema lenses have always been fully supported on our PL and OCT 19 mounts, but some camera/lens combinations required using a $20 spacer between the unit and our 72mm achromat. Given the number of PL/OCT19 mounts we've provided to our customers, suggesting that cinema format lenses cannot be used with the non-flipped Brevis is incorrect. In fact, Paul has been shooting PL mount cinema lenses almost exclusively for the last year.

I named a specific cinema lens, and did not generalize. I know that PL lenses work with the Brevis. Please, re-read my post and note the specific lens set mentioned.




In any case, I think most will agree that the flipped image, increase in edge sharpness, and reduction in CA balances nicely with the extra weight and .2 stops or so of light loss :-) Lenny's observation that at f2.8 the system is a stop faster than the units tested bodes well for folks using slower wide angle primes and zoom lenses.

It's good to know that I'm not crazy in seeing that the Brevis Flip improved the image enough to be mentioned. While I know that people have been fine with the image from the Brevis unit without the flip, would you suggest adding a Flip Unit to the package to increase the unit's ability to deliver sharper imagery in conjunction with your available screens?

I have seen the Brevis in action, in person, once before and had trouble with the clarity on either the left or right side of the image. I could see, when paired with the flip unit, considering using one because of the footage posted showing improvements.

[USLatin]

Ok, guys, please slow down for me cause my head is running slow tonight... :)
maybe I need to read this again tomorrow morning with mah cup o' kofey

Does it seem that the Brevis is significantly faster than the Letus at smaller apertures? Cause that's what I think I am gathering... and if so, it seems the benefits start to show at 2.8f already...? I am hoping to get two 2.8 zooms.... maybe this is the selling point for me?

I need a head to head between the flipped Brevis and Letus Extreme with at least 720p footage uploaded and a chart or at least some numbers on speed...

[Dennis Wood]

That is correct. Lenny is saying that at f2.8, the Brevis is 1 stop faster. That's half the amount of light required :-) The gap widens as you stop down the lens.

I regularly test with inexpensive f3.5 to f4.5 zooms (not everyone has a 20K lens collection at their disposal), and at this aperture, the Brevis is likely between 1.5 and 2 stops faster than everything else out there.

[Barry_Green]

That would defy the laws of physics.

[Kholi]

That is correct. Lenny is saying that at f2.8, the Brevis is 1 stop faster. That's half the amount of light required :-) The gap widens as you stop down the lens.

I regularly test with inexpensive f3.5 to f4.5 zooms (not everyone has a 20K lens collection at their disposal), and at this aperture, the Brevis is likely between 1.5 and 2 stops faster than everything else out there.

If both units lose the same amount of light, how can physically chopping light out (shutter blades) make a difference?

I need someone with a Brevis in LA to show me this phenomenon where you stop a lens down and see NO change in how much light is hitting the lens. While 1.4 - 2 you BARELY see a light difference, you still see the difference if you're looking. I'm just completely confused on how the Brevis manufactures light.

[Douglas Villalba]

I hope that people reading this thread are smart enough not to take everything that is said here as the absolute truth. Specially by companies and their reps that without proof claim that one is better than the other.

Anyone with a little technical knowledge knows that if you close a lens by 1 f stop you need twice the amount of light regardless of the adaptor.

[USLatin]

But I have heard of this before... and NOT from the guys at Cinevate. I just want to understand what is this whole thing about the Brevis not being linear... not losing as much likght as you stop down on the lens and so on... because I have heard it from two guys now... one a Brevis non-flipped owner and the other an SGpro owner who only got to use a Brevis!

Barry, Kholi, you guys know WAY more about me, please look into it if you are curious about this.

[philip bloom]

The brevis is very sharp. Shot some crystal clear images with it over the past year

[USLatin]

Philip your Piccadilly Circus shots were on a Letus right?
Do you have these sharp images on the Brevis hosted somewhere?


And Barry, could you please elaborate a bit on the physical impossibility of the non-leniar'ity of the light loss of the Brevis? I mean how come people that don't even know each other are saying this?

[Dennis Wood]

The fact that the Brevis does not lose light in a linear fashion that corresponds to the taking lens is a well known, commonly observed fact amongst our users. It is very, very hard to believe as you watch an aperture go from f1.4 to f2.0 to f2.8 (50% reduction from f1.4, then 50% area reduction again from f2.0 to f2.8). We are not defying physics here at all...the imaging elemnent is a break in the optical chain. The physics at work at the imaging plane simply do not correspond to conventional thinking regarding aperture and light loss.

Lenny measured the Brevis at just over a stop faster then the Letus EX with the taking lens at f2.8. I can't speak for the Letus, but his findings are absolutely consistent with our own findings here. With the Cinevate flip, the numbers would be closer to .7 stops at f1.4 and virtually the same, .7 stops as the 50mm lens is stopped to f2.8.

Don't take my word for it. Attach a Brevis to any camera and connect it to a waveform monitor. Stop the lens done from f1.4 to f2.8 and you will see exactly what I, and every one of our customers is talking about. Douglas, there is nothing I've said in this thread that any Brevis user could not confirm for themselves in about 10 seconds of testing :-) This is why we really think adapters should be tested for light loss with a standard f1.4 50mm mounted at f1.4, f2.8 and f4.0

Cheers.

[Lenilenapi]

Look guys,
I've been through these discussions before. Awhile ago I noticed that different adapters had different DOF's. Actually Dennis first mentioned it to me and I thought he was nuts. "That's impossible" guys like you argued... "DOF has to due only with f stop , etc, etc, etc." I was even arguing with Barry about it. Now everybody here seems to recognise that its true, because they've looked for it and can see it themselves. Its an observable fact. Theory comes after abservation.

Well its the same deal with linearity, and all you have to do is open your eyes and compare adapters and exposure. Its simply an observable fact.

Yes in a normal situation if you close an iris one stop you reduce light 1 stop. However the adapters are different because you are looking at the image through a diffusing screen that has its own properties and you are looking at it from a distance away so how that screen scatters light affects everything from DOF , to exposure, to gamma, and nature of the Bokeh.

Measure it yourself. It may be different on different video cameras, but on an HVX I promise you that a pre-flip Brevis CF1L will only very barely react to the change in light from 1.4 to 2.8 on the 35mm lens. Its simply a fact. Other units haver their own linearity "footprints".

My own theory is that because the Brevis is a less dense screen it simply doesn't scatter the light from the outside of the wider iris enough to make a difference when observed from a distance. (similar to vignetting perhaps.) The flip optics could change that entirely. Its both good and bad. You get no advantage from a fast lens, but you also have a very fast adapter at f2.8.

The other units each have their own characteristics but these need to be taken into account when comparing speed among other factors.

BTW I've been in this business for many years and used to run a film rental department so i'm used to lenses and collimation issues.

A number of these issues I think deserve a sticky so we don't keep going around in the same circles. Back focus is another. I would love to see one for DOF, Linearity, and back focus. I've suggested it before but no one seems to respond.


Lenny Levy

[Barry_Green]

The amount of light that is transmitted to the ground glass is governed by the aperture of the 35mm lens. It determines how much light gets through. If you stop it down by one stop, 1/2 as much light gets through. The adapter has nothing to do with this, this is all happening at the lens level, before the adapter even factors into it.

If the claim is as I understand it to be, it's simply not possible and not rational. Here's a simple example:

Let's say there's a light source that's outputting 8,000 footcandles. We have a lens that's set to f/4.0 (for sake of clarity let's pretend there's no light lost by the lens, and f/4.0 = t4.0 in this case.) The amount of light exiting the lens will be, for sake of argument, 500 footcandles.

That's a mathematical fact, a given. The amount of light getting through the lens is restricted by the lens' aperture. If we stop that lens down to f/5.6, then 250 footcandles will exit the lens. If we stop it down to f/8, 125 footcandles will exit the lens. Make sense?

Okay, so now we introduce an adapter into the equation. The adapter is primarily a ground glass screen, with perhaps a diopter and maybe a condensor lens involved. This optical path is going to result in some light loss, especially the ground glass portion. So let's say the ground glass and other components eat up a full stop of light, right? So, if our lens is transmitting 500 footcandles, the adapter's optics will eat up 250 footcandles and transmit 250 footcandles.

Simple math, simple light transmission, right?

So, if we close down the aperture on the 35mm lens by one stop (to f/5.6), we'll get 250 footcandles (instead of 500) exiting the lens. The adapter will see 250 incoming footcandles and transmit 125. So the total relationship of incoming light to exiting light stays constant.

If we close down another stop, to f/8, we'll now have 125 footcandles exiting the lens, and 62.5 exiting the adapter.

If we close down another stop, to f/11, we'll have 62.5 footcandles exiting the lens, and 31.25 footcandles exiting the adapter.

What has been claimed is that the Brevis will, when the 35mm lens is stopped down, actually be faster than other adapters, and the more you stop down the lens, the more the gap grows (i.e, the Brevis will grow to be 2 stops faster than other adapters.) How? How is this possible? The amount of light entering the adapter has been consistently, mathematically, chopped in half. Yet, somehow, the Brevis must be "manufacturing" or "creating" light in order for this "performance gap" to increase. It's receiving a limited quantity of light that's directly cut in half for every stop that the 35mm lens has been stopped down -- how can it possibly "widen the gap" to appear to be two stops faster than another adapter? It can't.

The only possible way I can think of for there to be any sort of observable effect for this would be that there's some sort of condensor lens that's amplifying and magnifying a hot spot in the center of the frame (like a magnifying glass takes a wide spread of light and concentrates it into a tiny pinpoint which is super-hot). If that's what's going on, then I could see results like these claims showing up, but I would also expect it to be accompanied by a significant amount of portholing/vignetting.

It is a very curious claim that's being made, and one that does not seem scientifically supportable. I also would like to test this. Anybody in the San Diego area with a Brevis who'd be willing to donate it for a day so I can try some experimentation to get to the bottom of this?

[Barry_Green]

Added: I have also noticed some nonlinearity in the very-most-open stops, being f/1.6 to f/2.0 on an HVX (without any adapter involved). At those most-open stops the lens doesn't appear to respond completely linearly; stopping down from 1.6 to 2.0 doesn't result in 2/3 of a stop of light reduction. As to why, the only explanation I can come up with is that the HVX CCD probably uses microlens technology over each pixel, and the extra light entering the lens through the wider aperture is hitting at such an angle that it's not being "seen" as efficiently by the microlens.

However, none of that has any bearing on how an adapter works. The adapter looks at a constant display (the ground glass screen) and light is transmitted through that at a constant rate of scatter, due to the pattern of the ground glass. As to why we see nonlinear response with all the adapters from 1.4 to 2.0, I don't know that answer yet, but I haven't seen an adapter that performs differently, they all seem to ignore anything more open than about 2.0.

[Lenilenapi]

Barry,
I love you but your totally out on a weak limb here and basically misusing the scientific method. We don't use science to disprove observed facts - that's medieval thinking really. We use science to make sense of observed phenomena. This is an observed fact. Just because you haven't seen it doesn't mean that others haven't. They have.

My partner gave me the same routine for a month unitl I showed it to him. Its a fact - you can come up with a theory of your own to explain it but I think mine isn't half bad.

If you measured the light at the film plane I think it would be linear as a film or chip would react, but you are seeing only what's visible from a distance away as transmitted by a dirty piece of glass. If the glass was smooth enough in fact you wouldn't see an image at all. Adapter optics are a wrinkle all their own.

Do you still disagree that different adapters display differring DOF? That's also an observed fact.

By the way I don't think that the Brevis is manufacturing light, that may be why its hard to understand - I think its the opposite - it only sees the light at 2.8 and doesn't see anything from the wider iris. Seems quite reasonable to me - plus of course - it is a fact!

I would expect it to be accompanied by more vignetting but it doesn't actually seem to be, but that may be due to all the work dennis has done on picking screens - I don't claim to understand it and haven't tested nearly all the parameters.

Hold it though I just saw your last post - are you agreeing that it happens on the others from 2 to 1.4. Why are arguing about it then. Same deal on Brevis, just more pronounced.
By the way in my experience the Redrock was more linear. My theory- denser screen- more linear - more scattering from the wider iris. Just a cheap hypothesis though.

Lenny Levy

[Kholi]

I said the same thing: From 1.2 to 2.0 there's a hair of difference. 2.0 to 2.8 it shows up on the LetusEX.

And, as far as light loss in general is concerned, I suspect the reason is different zoom settings between the adapters. Might have to gather them up and see how much light's loss from the HVX itself between the different zoom settings.

The good thing is with the flips out, every single test should be able to zoom to the exact same number for each adapter, ruling the camera out where light is concerned.

[Dennis Wood]

How is a camera connected to a waveform monitor not scientifically supportable? It measures both edge falloff and differences in light levels so I can say with certainty that the scope starts as a straight line in our test (lit white board) and stays that way as you stop down the lens. Not to quibble, but what I'm stating has been well documented by our users. From f1.4 to f2.8, there is little to no change, and from f2.8 to f4.0, you'd see about half a stop. (Lenny has indicated that the Letus EX is losing just over one stop from f1.4 to f2.8...which suggests the Brevis at that same aperture would require half as much light.) The camera zoom settings are irrelevant in this testing because they are not touched as the taking lens is stopped down from f1.4 to f2.8, to f4.

On the other hand, when testing a bare XH-A1, and a bare HV20, a change from f2.8 to f4.0 did show a 20 IRE change consistent across both cams, when the camera was set up at 50 IRE to start. That's exactly what our optical engineer had predicted, assuming we tested at the middle of the gamma curve.

I should stress that I have never, (and will likely never) use or test any other adapter out there...so I am definitively speaking based on extensive testing with the Brevis system only. We have way too much respect for our customers to make any of this up :-) I'm mystified as to why the discussion is consistently so hotly debated given that there are now a large number of Brevis owners making the exact same observation as we've been maintaing for 18 months or so. What I will commit to is a clip that will settle the discussion for good...it's actually done already and incorporated into Cinevate's "Video Univerity" series on image tuning. I"ll have Paul pull the clip tomorrow which shows the scope, camera LCD, and me stopping the taking lens down.

[USLatin]

Wow Barry, this sounds like something that you've been thinking about in the back of that big ol' head of yours for some time now. I would love to see it go to the front burners of your mind for a day or two.

If I had one I'd drive down with it for you to but the best I can do is ask if anyone I know with one will ship it to you. Thanks for your posts.

And thank you too Dennis and Lenilenapi.

EDIT: Thanks Kholi, what you point out about the zoom setting sounds promising to my uneducated ears... Barry?

[USLatin]

Dennis, just to clarify... does this phenomenon remain with the flip module mounted?
I think you've said a few times that it does just not as pronounced... is that right?

Sorry... I am trying to keep up with you guys

[Lenilenapi]

I think the difference in speed is generally due to the density of the screen though zoom plays a part as well. You can measure how much zoom matters by testing it without an adapter. I think you'll find if you start at say 2.8 on the video camera you'll see very little difference as you zoom at least until the very long end. At wide open there is greater affect.

Lenny Levy

[Kholi]

I think the difference in speed is generally due to the density of the screen though zoom plays a part as well. You can measure how much zoom matters by testing it without an adapter. I think you'll find if you start at say 2.8 on the video camera you'll see very little difference as you zoom at least until the very long end. At wide open there is greater affect.

Lenny Levy

When you get a chance, actually put it to the test with the adapters on and tell us what you get. Camera @ 2.4 or2.8 is fine, a lot of the time that's as far as you can get the iris on the HVX down when doing indoor shooting, anyway.

Open would be just as good.

Better YET: Why hasn't anyone RECORDED this in action? We can see what YOU see when you hit the record button, so please show us how this works. Record the stopping down from 1.2 to 2.8, then 2.8 to 4 so we can see how little it makes a difference first hand.

[Dennis Wood]

US, the flip module changes nothing with regard to the linearity of the response to aperture changes (or lack of!). You just need to add .1 to .2 stops to the non-flip numbers :-) The hidden benefit in all of this to Brevis users is that you can confidently stop your 35mm lens down to the f2.8 to f4 range (where most are noticeably sharper edge to edge) without losing much in the way of light.

[USLatin]

Excellent, thanks for saying it like that for my "simple mind" :)

Is there any chance you could mail a used Brevis that you might not be using to Barry for testing? I don't think I have anyone willing to let go of their adapter :)

[Barry_Green]

US, that's nothing that has been rattling around, that's just top-of-the-head stuff.

There are several claims that are made that just don't make sense. I like things to make sense. There was once a claim that a Brevis was actually *brighter* than not using the adapter. This is, of course, impossible. Then there was a claim that in the Philip Bloom test, the more you stopped down the Brevis, the more the difference between it and an M2 (i.e., maybe the Brevis lost 1 stop at f/4, and the M2 lost 2 stops, but by the time you got to f/8 the Brevis was losing maybe 1/4 stop and the M2 was still losing 2 stops -- I'm making up these numbers but the concept jibes with how I remember the info being presented). That's what I'm calling into question here -- it does indeed seem completely impossible. There has to be some other factor at work.

As for taking users' reports, I don't find that's the most reliable indicator of factual accuracy; just like the pollsters found out in the New Hampshire primary. People are out there saying that the HV20 is "better in low light" than a DVX -- they'll swear by it. Even though it's absolutely completely entirely wrong. There were people "testing" and declaring that the Red had no rolling shutter artifacts, and that the EX1 had no rolling shutter artifacts, even though they most definitely both do have them.

If people are happy with whichever product, great for them, that's the state we'd like to see all users achieve. I'd much rather see people walk away from the endless discussions and debating and just get out and start putting their products to work. But I also am a stickler for accuracy; I'd like to know what is actually happening and why.

[Barry_Green]

Oh, and as for adapters for testing -- we tried to put together a call to all manufacturers for adapters so we could get to the bottom of all this. Not surprisingly, nobody offered an adapter -- except Cinevate! They were the only ones who said they would participate, but the timing didn't work out, and that was a while ago. But Dennis was willing to put his up for comparison, which speaks well for his confidence in his product.

[Lenilenapi]

Barry, You're right that claims are made all the time on here that are complete nonsense. Personally i have never made any claims for any adapter like those you mentioned.

I was personally curious enough about all the BS about these adapters that I bought three of them - actually 4 including the Redrock.

The only thing I would appreciate is that when responsible people ( I consider myself responsible) make observations, especially when they that are supported by others, you don't just dismiss them by calling them unscientific or impossible. Wait till you're able to make your own observations.

Lenny Levy

[USLatin]

So I guess Dennis might send you an adapter now even if it is not alongside all other popular ones. We trust your word, at least I do. I have not made up my mind yet, but it in fact the Brevis is at all faster at 2.8f than all others then I think I will be sold as soon as I see some of that flipped HD that people seem to be extremely happy with... even if I have to get the flip for it to be 100% sharp, which is something I wasn't planning on. If all goes well with my plan I will need the best 2.8 performance I can get so I can get the 28-70mm and 80-200mm zooms as I keep thinking about. Of course there are several friends I've made here that are trying to steer me towards primes instead, but I am stubborn and will only go prime if I absolutely positively have to. It is because of this that I am so interested in this folk myth being tested... I am cautiously optimistic about it too. Not knowing a 48th about lenses as you do I am solely basing my limited optimism in the fact that I have personally heard two completely separate people say something of the sort... so I will wait for some of that Barry posting that I enjoy only as much as I used to enjoy reading about Autobahn escapades on M3's on the pages of Road & Track.

Not that you write like those middle aged crisis ridden folks... hehehe... you are much more objective.

[StMad]

FWIW, I agree with Lenny (and others) about the Brevis' non linear response.

Barry, if you don't know, please don't say you know. "Statements of fact" here and on the EX1 board are leading to much confusion and angst. Your opinions carry much weight.

[Dennis Wood]

I'm going to shoot a little demo today that will make this visually clear. I accept that it's very hard to believe, incredibly counter-intuitive, and I would not have accepted the observation had I not quantified it myself. If nothing else, it will spark a great discussion, and I hope illustrate a different way to measure light loss on adapters in general :-) Our R&D budget has been extensive, and with six different imaging elements to shoot with, we have extensive data on the issue of light loss and linearity. CF1Le and CF1 are purpose designed to achieve maximum light efficiency, particularly as you stop down the lens. They are also a very good film match with regard to bokeh in our tests beyond f2.8

The difference Phil Bloom demonstrated is here: http://web.mac.com/philip.bloom/Shootout/Page_4.html Note that the taking lens was at f8 ...and check out the HVX settings. The Brevis grab is still overexposed by a stop or two in that shot!

For f1.4 to f2.8, CF2Le and CF3Le are a better match to film bokeh...but lose more light. The important thing is that our users can choose what works best. With our next CINEFUSE release, anyone doubting the importance of drop-in imaging elements will likely change their mind :-)

[USLatin]

Great! Dennis, thank you for doing this... I hope you can host it in 720p! Let me know if you need bandwidth I should have a few thousand GB left over hehe...

Secondly, when you said "CF1Le... particularly when you stop down the lens... very good film match with regard to bokeh in our tests beyond 2.8" and "for f1.4 to f2.8, CF2Le and CF3Le are a better match to film bokeh... but loose more light".
If I were to use only the 2.8f zoom lenses, would I be in that bokeh sweet spot with the CF1Le wide open or should I still go with the CF2Le which you recommended once when you didn't know about my uncommonly slow lens choice?


With our next CINEFUSE release, anyone doubting the importance of drop-in imaging elements will likely change their mind :-)

When is this happening? And what should we expect?

StMad, I think Barry will get to the bottom of this. His posts were only questioning the possibility of this unexplained and unprecedented behavior. He is writing in the tone of someone searching for an elusive explanation for something which down right weird as heck. Since he expressed his willingness to test this phenomenon I trust he will continue to weight in on discussions regarding it and in doing so he will again be carrying the free-marketing factor in his posts. Also, as you no doubt know, he will be making use of his unbiased approach to render his opinions useful to the community as he has been doing since way before you and I joined back when the HVX was a rumor.
I really hope he can get his hands on one, because if he records this, not only will we get a great guide on how to take advantage of it and an in depth explanation as to it's pros and cons if there are any, but better yet, he might become so curious as to why it does happen that he won't stop till he has a scientific explanation for it..?

[Barry_Green]

Forgive the frustration. Several claims have been made that appear to defy scientific fact -- such as the idea that using an adapter can actually "gain" light.

So I guess I'm faced with two choices -- either let seemingly outrageous claims go unchallenged, or have to buy every product that comes on the market just to find out if it can do what it says it can. Fine. I'll buy a Brevis. I have no need for it, I've bought and/or tested and/or used every adapter on the market but the MovieTube, I've tested them in all manner of circumstances and find them all to behave similarly to one another and in accordance with the laws of physics. But now we have one particular product that makes claims (either from the manufacturer or from users) that simply do not correlate with the rest of the observable body of evidence, and according to St. Mad and others, I'm not allowed to point out that something just simply doesn't make sense here? That there is no "free lunch," there's always a piper to pay, there's always a compromise or a tradeoff, and if you're seeing evidence that seemingly defies observable and reasonable/rational explanation, there's got to be some downside or side effect.

And the only way to get to the bottom of it is to test it. I've taken the rational approach of repeatedly asking around for other users to loan a unit so I could get to the bottom of it, and that hasn't happened (which is, of course, perfectly understandable). I guess the only recourse is to torch a thousand bucks?

Fine. So be it. Maybe while I'm at it I'll torch another seven thousand on an EX1 just so I can be allowed to talk about that emperor's clothes too?

I mean, what's the alternative? I guess this is the same spot lenny came to, where he had to buy three of 'em. And even then we get conflicting reports where Tim Naylor and Lenny's tests directly contradict each other... maybe there's no other way.

[Kholi]

Part of the claim was that it behaves in this extraordinary way while the others don't.

Also, I was trying to contribute a solution - to get a ball rolling.

Thanks for the input.

Others don't. My LetusEx doesn't defy physics. My M2 Didn't defy physics. I get what you're saying, the actual point was that the Brevis was the one that he wanted to test about the defying o'physics.

Which means it's as simple as getting Barry a unit and the Cinescreen in question to test for himself.

[jenningsp]

do it barry, do it! buy that ex1 and the brevis. do you own an sgpro? buy that too!!!

does anyone know why the spinners footage looks 100x more awesome than ALL of the non-spinners...? it's not just the bokeh or the extra diffusion... it's something else...

for some reason the "in-focus" stuff from the non-spinners looks like it's video. so if you've got a scene where everything is in focus, it looks like video...
but with a spinner, all the footage looks awesome!!!! all the in-focus stuff looks like silk.

i'm not sure why this is... everything i've scene from the M2 and the SGpro looks awesome! but half the stuff i see from the brevis and the letus just doesn't excite me, some of it does look awesome, but some doesn't, it's about 50/50.

i own a letus35a myself and it exhibits the same non-awesomeness quality as the other non-spinners. i've shot some awesome footage with it, but i've also shot some non-awesome stuff.

i am one of those people who obsesses about how my image looks. i can see the difference very clearly. i know some other people can too. i just want to know why?

awesome

[Kholi]

do it barry, do it! buy that ex1 and the brevis. do you own an sgpro? buy that too!!!

does anyone know why the spinners footage looks 100x more awesome than ALL of the non-spinners...? it's not just the bokeh or the extra diffusion... it's something else...

for some reason the "in-focus" stuff from the non-spinners looks like it's video. so if you've got a scene where everything is in focus, it looks like video...
but with a spinner, all the footage looks awesome!!!! all the in-focus stuff looks like silk.

i'm not sure why this is... everything i've scene from the M2 and the SGpro looks awesome! but half the stuff i see from the brevis and the letus just doesn't excite me, some of it does look awesome, but some doesn't, it's about 50/50.

i own a letus35a myself and it exhibits the same non-awesomeness quality as the other non-spinners. i've shot some awesome footage with it, but i've also shot some non-awesome stuff.

i am one of those people who obsesses about how my image looks. i can see the difference very clearly. i know some other people can too. i just want to know why?

awesome

You're blaming the adapter for something the shooter takes responsibility for. Gonna tell me that Phillip Blooms LetusEX footage looks like that?

AND, upon looking at the Phillip Bloom Brevis shots further... My theory is that it's a huge hot spot.

[jenningsp]

i've seen most of phill's footage. his letus and brevis stuff with CF1 and CF3 exhibits the same thing i'm seeing on the other footage...

phill tends to shoot static shots, and the "difference" i'm seeing only really becomes apparent when everything starts moving, like people walking, moving water (this is a big one) that sort of thing...

also nighttime stuff looks a lot better than daytime stuff with the non-spinners.

phill likes to add vignetting in post to a lot of his footage. so that might explain the "hot spotting"

again it's 50/50, half the stuff from non-spinners looks great, the other half doesn't look so great. it's all better than no adapter at all though :D

[Kholi]

i've seen most of phill's footage. his letus and brevis stuff with CF1 and CF3 exhibits the same thing i'm seeing on the other footage...

phill tends to shoot static shots, and the "difference" i'm seeing only really becomes apparent when everything starts moving, like people walking, moving water (this is a big one) that sort of thing...

also nighttime stuff looks a lot better than daytime stuff with the non-spinners.

phill likes to add vignetting in post to a lot of his footage. so that might explain the "hot spotting"

again it's 50/50, half the stuff from non-spinners looks great, the other half doesn't look so great. it's all better than no adapter at all though :D

Definitely not doubting your observations. I notice a lot of stuff that others tend not to as well so I'll keep an eye out. I think most of it has to do with things outside of the adapter realm, though: composition, shot choice, etc. There's lighting to consider: The M2 has been used on more narrative work than any other adapter. Given that track record, you're chance of seeing really GOOD work versus Run-of-the-mill-back-yard-trees is greater.

A great example of narrative work with the LetusEX is Jack Daniel Stanley's "A Little Mouth To Feed".

[Douglas Villalba]

I don't always agree with Barry, but I think that anyone that has knowledge of how light works has to agree with him on this one.

Simply put my HVX without an adaptor has a ASA (ISO) rating of 320. Now add the LEX with a lens and it drops down to 200. Brevis user and builder claim that at f 2.8 the Brevis is between 1 and 2 f stops faster than the other adaptors. If the Brevis is only one stop faster the LEX (I use the LEX because I own one) that would make the ASA raring 400 on the HVX. That would mean that the Brevis is creating light since without and adaptor I started with an ASA rating of 320.

I could understand that their GG is not too sensitive to over exposure and you see no actual difference from f 1.4 - 2.8.

If I were a manufacture of an adaptor and really believe my claims, I would jump on a plain to show Barry my product. Even if just for the exposure I would get my product.

I believe that all the adaptors have + & -. Some LOOSE less light than others. Some you are able to use faster shutter speed, but by the law of light traveling they all have to loose light.

I would also offer my studio in Miami to conduct a review just for fun. I already own the LEX and HVX. My friend owns the M2, LEX and recently ordered the SG. If you would like be included just drop me a note. Preferably if you own any of the other adaptors.

[jenningsp]

yes the context, professionalism, composition and lighting have a great deal to do with how the image looks. but what I'm talking about goes beyond that.

it's an inherent trait that spinners give the image. there is a quality that i can't quite put my finger on. i'll call it "awesomeness" for now...

different adapters, namely their GG's, give a certain "look" too the image. and for some reason spinning adapters look "awesome" 100% of the time and non-spinners look "awesome" only 50% of the time.

i actually watched half of "a little mouth to feed" when it came out, but my download stuffed up and never finished it. still, it still had that same quality i'm talking about.

[USLatin]

Barry... are you really going to buy a Brevis? Dennis, why don't you let Barry pay shipping and let him have a Brevis for weekend free of change if at all possible... this should definitely be nothing but good for your product, especially if it is finally proclaimed the fastest adapter out there. I think a review by Barry that concluded just that would translate to the acceptance of it's supremacy in terms of speed for 80% + of DVXuser members. That definitely can't be bad for sales :thumbsup:

Jenningsp, maybe it has to do with consistency on all the GG's effects on the picture all the way to the shorter shutters given the higher speed of the grain?

[Dennis Wood]

Ok, here it is. Forgive the audio but we fired this together at the end of the day...should be fairly self explanatory. Please right click and "save as". The file is a 35MB quicktime file that runs about eight minutes.

http://www.cinevate.com/images/lightloss.mov

The camera used was the XH-A1, with no presets loaded (default config) with everything set to manual. AGC was off of course. We've tested on 3 different cameras (HV20, XH-A1, XL2) to confirm that when baselined to approx 50 IRE on the waveform monitor, a 1 stop difference (on the camera)corresponds to ~20 IRE on the monitor. We used Adobe OnLocation on the laptop, with output directed via HDMI to the 42" LCD so you could see clearly what was going on.

Seriously, we don't ask folks to buy the adapter for reviewing purposes...never have, and never will :-) As Barry has already mentioned, we were all lined up to send one for the shootout...and we were apparently the only adapter manufacturer that was willing to do that. At least one third-party review of the flip vs non-flip Brevis has been done, and should be up any day now.

Please, if you've invested your hard earned dollars in one solution or the other, then the best thing you can do is shoot with it, learn it's quirks and limitations, and ignore this thread. If you'd like to see what I think is some very cool stuff, check the clip...and try it with what you're using. At the worst, you'll figure out how much light to bring along, or leave at home for your next shoot :-) Does it lose light? Sure. Does it lose what you'd predict based on convention (that doesn't apply here)...absolutely not. Moving from f1.4 to f5.6 on the 50mm lens mounted to the Brevis flip with CF1Le resulted in about the same light loss as stopping the bare camera down 1 stop.

[Kholi]

Okay, I suck at reading waveforms and was hoping to see some actual footage. But as mucha s I suck at reading waveforms, does it read that with the Brevis on there's a non-uniformity with light to begin with.

The sides are lower than the center, and the bar's got lumps in it from the get go.

Hot Spotting?

Edit: Considering if it were a hotspot in the Cinescreen (is that what it's called?) then the hotspot blows colors out? Is that why the colors of the Brevis Unit in Phil Bloom's tests look strange?

Does anyone have a Brevis unit in Los Angeles?

[USLatin]

Dennis! I see you! hehe... thanks for the little video!

I am thinking aloud here... does this behavior happen with any lens or only with certain ones? Or does it happen with all lenses and just slightly differently with each?


Okay, I suck at reading waveforms and was hoping to see some actual footage. But as mucha s I suck at reading waveforms, does it read that with the Brevis on there's a non-uniformity with light to begin with.

The sides are lower than the center, and the bar's got lumps in it from the get go.

Hot Spotting?

Yes, it seems the center and either side are slightly different, but at times it was backwards... so not always necessarily "hot" spotting... I'd love to see a white page on a waveform with a different adapter to see if this is also present and just how pronounced if it is

[USLatin]

I wonder if the adapter not being screwed in has something to do with some of this edge fall-off?

but man... a little hot-spotting for a big chunk of light...? I gotta see some of that flipped HD hosted somewhere! I have to look for that drop-off on the edges and gauge how pronounced they are...

but what I'd really like to see is some footage of the same subject (something that would help point out hot-spotting) and see the same thing all different stops on two or three lenses, one being a focal length far from 50mm just to change things up a bit

[Dennis Wood]

The behaviour changes of course with different lenses, but the relative exposure curve is very similar. We always baseline with the 50mm f1.4 as it's nearly ubiquitous. I've always indicated that slower zoom lenses work amazingly will with CF1Le...and that light efficiency is why.

The sharp edge falloff on the right/left represent the black edges of our imaging element gate in the overscan area. The thickness of the line is coming from an underexposed imaging element...note the shutter speed! What you're seeing there is the grain itself in the imaging element that was not moving. You can actually use the scope with a stopped down 35mm lens to set dead-accurate back focus by observing the grain effect on the scope.

[Kholi]

The behaviour changes of course with differnent lenses, but the relative exposure curve is very similar. I've always indicated that slower zoom lenses work amazingly will with CF1Le...and that light efficiency is why.

The sharp edge falloff on the right/left represent the black edges of our imaging element gate in the overscan area. The thickness of the line is coming from an underexposed imaging element...note the shutter speed! What you're seeing there is the grain itself in the imaging element that was not moving. You can actually use the scope with a stopped down 35mm lens to set dead-accurate back focus by observing the grain effect on the scope.

Thanks for explaining that.

[USLatin]

Ok, but the higher exposure should still be a straight line till it gets to the very edges and overscan yet I see an ever so slight belly in the middle... it looks to be about 5% difference at most which given that it is a gradual curve it should be very hard to notice and it isn't as pronounced under all settings... right?

1.4f and 2f and 2.8f
seems to be a bit darker in the center by far less than 5%, and also the curve seems to be completely consistent at all of these

4f
seems to be completely flat

5.6f
seems to have a slightly irregular hot spot in the center

Now if this is from the grain just as the line is not a thin line from grain adding "dark spots" of grain all over the screen and it is the grain that will have the hot spot in the center at 5.6f or ever so slight "cold" spot in the center at 1.4, 2, and 2.8 then there will be irregularities only in the exposure of the grain across the screen... but if the grain is not consistent then the image projected isn't consistent either because they are one in the same...

which also brings me to what I think is a realization that the GG allows for different "exposures of the same area by one "grain" being darker than the one next to it and this might help mimic the dynamic range of our eyes? well... I'd ignore that las thing if you know what's good for you cause it is a thought of which I have little grasp of if at all and even if I were able to explain it it is veryl likely WRONG anywhay :)

[USLatin]

BTW it looks like I might have to get more ND filters than just the one filter equivalent to half the built-in ND's in the HVX which I was planning on getting!

I really want to see some flipped Brevis HD shot on the HVX now! :D

hehe...

[Lenilenapi]

Look guys therte is absolutely nothing in what I have described that defies any laws of physics or optics. Now I do think it has sometimes been described inaccurately as "gaining light" which is I agree is impossible. Dennis may have used that expression at one point and I told him I thought he was describing it backwards. But if you'll bear with me a moment I will try to explain what is happening as I see it.

The Brevis CF1L with its less dense screen seems to be "faster" than the others which makes perfect sense as it is diffusing less thus allowing more direct light through. With the 35mm lens at 2.8 the difference in speed (or better "transmission") is noticable so the Brevis seemed perhaps as much as a stop faster in my tests. It is also noticably a less "diffused" image which by the way is not neccessarily the same as sharpness

However related to the greater transmission it seems to not react to the wider f-stop as you go from f 2.8 to f1.4. This is NOT a physical impossibility and presumably it must have something to do with the viewing angle we are at with respect to the image on the screen. It is probably akin to vignetting but it is probably not quite the same and Please Please Please - don't use this as an excuse to claim the Brevis will vignette more, because I haven't seen that. Its possible but I haven't seen it, nor have my clients. Lets make vignetting another thread OK.

At any rate, because it doesn't react to the wide f stops, it loses its speed advantage as we open up to f1.4, because for some reason the denser screens seem to pick up more of the light from the wider apertures.

This is not illogical or crazy in the least. You all agree that you have seen this phenomena on the other adapters but not to such a degree. Barry noted that some don't seem to notice anything from f2 to f1.4.
I seem to recall that the Redrock ( the densest of these screens) reacted the most linear between f2.8 and f1.4. I believe it was almost 2 full stops. Thus the Redrock became comparatively faster with the wide open lenses.

Though I haven't done any careful tests , I have noticed that there can be non-linear behaviour on the other end as you close down the iris. On one of these guys I remember seeing the light reduce more and more as the f stop narrowed. Can't remember which one.

Does this make any sense to you guys.
As with the DOF issue - these adapters act in odd ways that we don't expect. It doesn't neccessarily mean that the observers are quacks, but that we need to change our understanding. That said it also important to be skeptical and not trust every wacky claim you read on these pages.

By the way. I have no experience with any other claims or tests run by Dennis or anyone else on this forum, and I can't get Dennis test to play so a healthy "no comment"from me.

Lenny Levy

[Lenilenapi]

Incidently, I don't think Tim's and my tests were so far off as to be in "direct contradiction" His Letus was a touch faster, and mine a touch slower than the SGPro but they were less than a 1/2 stop off the SG in both cases. and I was using a Rev 2 and he had a Rev 3.

Wayne swears they are the same but Tim thought that his Rev3 was maybe slower than his previous version. Everything else about Tim's test I pretty much concurred with, though I felt it was unfair to talk about sharpness without carefully checking focus on a chart as part of the test.


lenny

[Michael Friedman]

The math Barry cited applies if you were shooting just the imaging element from the front (like a movie screen).

Instead, you are shooting through it (it is translucent) which means that your camera is still gathering light from the outside world. This accounts for little to no change at wide exposures since the opening of the aperture is still (likely) as wide as the imaging element. You are 'seeing' straight through - edge to edge.

[USLatin]

The math Barry cited applies if you were shooting just the imaging element from the front (like a movie screen).

So it is the light transmission of the GG that plays this "trick"... but I still don't understand how it would shave off different percentages of the total light on different total amounts of light?

Anyone know where there is some flipped HD?

[Lenilenapi]

It is reacting to the size of the iris and the angle at which the light from that iris hits the GG. Its not that hard to visualize how this could happen.
A denser screen scatters light in more directions is my guess, and so it would also scatter light from the more radical directions more to the center as well.

[Dennis Wood]

Leni, did you try VLC (videolan.org) ? I can re-encode to wmv for you if that works better...

US, the flip modules started shipping in volume a few days ago, so for now, this will have to do: http://www.cinevate.com/phpBB2/viewtopic.php?t=1496 It was shot using a preliminarly setup, so expect even better performance from the currently shipping unit.

[Barry_Green]

The math Barry cited applies if you were shooting just the imaging element from the front (like a movie screen).

Instead, you are shooting through it (it is translucent) which means that your camera is still gathering light from the outside world. This accounts for little to no change at wide exposures since the opening of the aperture is still (likely) as wide as the imaging element. You are 'seeing' straight through - edge to edge.
Well, if that's the answer, that's a great-big "duh" moment and a slap-my-forehead, why-didn't-I-think-of-that issue. If the iris is actually physically bigger than the screen and thus affording no occlusion, such that the adapter can "see" straight through... interesting. This would make no sense in the case of a solid surface (such as front projection) but if it's a transparent/translucent element...

But, wouldn't that run counter to the assertion that the Brevis is the one that's most immune to light changes at the largest apertures? As I understand your suggestion, wouldn't a smaller imaging screen be "fully bright" at deeper f-stops (since the camera is still looking "straight through"? Yet the Brevis has one of the largest imaging screens.

[Barry_Green]

Oh, and thanks to the incredibly responsive members of the DVXUser community, it looks like I'll be able to test a Brevis in Feb. after I get back from this Wounded Warriors school stint.

[Michael Friedman]

Well, if that's the answer, that's a great-big "duh" moment and a slap-my-forehead, why-didn't-I-think-of-that issue. If the iris is actually physically bigger than the screen and thus affording no occlusion, such that the adapter can "see" straight through... interesting. This would make no sense in the case of a solid surface (such as front projection) but if it's a transparent/translucent element...

But, wouldn't that run counter to the assertion that the Brevis is the one that's most immune to light changes at the largest apertures? As I understand your suggestion, wouldn't a smaller imaging screen be "fully bright" at deeper f-stops (since the camera is still looking "straight through"? Yet the Brevis has one of the largest imaging screens.

Yeah, it sort of just dawned on me today. I think it must explain a great deal of it.

As for why it is more apparent in the Brevis, I don't know. Perhaps it is the most translucent? I don't own one, I don't know. Maybe it has just not been tested as definitively on other adapters.

[StMad]

...and according to St. Mad and others, I'm not allowed to point out that something just simply doesn't make sense here?

Not at all, it's better for the community when you do. But you were being more direct than that and leaving less room.

I did my own test with my Brevis and SGpro with 50mm 1.8 Nikon, recording my HVX's lcd (with zebra) with my HV20. Not a patch on Dennis' test :), but it showed similar results - there was no discernable light loss from f1.8 to f4 (almost certainly less than half a stop). f4 to f5.6 appeared to lose 1 stop. The SGpro's light loss was linear (1 stop seemed to = 1stop).

Exposure changes (or lack of change) seemed to be consistent across the entire frame - but this is the most speculative of my findings.

I can post a quicktime but I'm guessing there's not much need after Dennis' effort.

[Dennis Wood]

Barry, Lenny is on the right track. There are a few concepts at play with our imaging elements that are not part of conventional optics thinking when it comes to f stops and the like. It is fascinating (regardless of one's prowess in physics) to quantify the interplay :-) I should have posted a test like this a year ago, but I assumed the light efficiency topic (gain, loss yada yada) had been resolved long ago with the Brevis.

[Kholi]

I would LOVE to see a Quicktime of the effect in real time. The Waveform explanation was a great one, glad the effort was made. I'm gonna strap the HVX and Letus up to On Location not to test the linearity of light loss, but the uniformity.

Does the Hot Spot theory make more sense with Michael's theory? If in fact the ground glass was just that thin and the Brevis screen is that much larger than the rest, that could contribute to the phenomena.

What really amazes me, still, is that Phillip Bloom was stopped down to F8 in that light and things were still too bright for comfort. Camera and Lens at F8? Wouldn't that make the image extremely hard to control in that case?

Edit: QUESTION FOR DENNIS WOOD--

How far is the ground glass from the actual lens of the HVX? Is it closer to the end of the unit or to the camera side? And, how close is the achromat to the actual camera Lens?

Someone in LA wanna let me play with their Brevis?

[Dennis Wood]

That's why I've also been guilty of the broken record effect regarding using external NDs with the Brevis. If you want more light control, we've got CFLe and CF3Le to do just that. Their response curves are different, and the swap only takes a few minutes. We learned early on that every shooter has a different idea of what the perfect adapter is. We're not there yet, but no one would accuse us of not pushing forward constantly to that end. Even in blinding sun on new snow, I've found a .9ND and polarizer adequate when used with the taking lens at f5.6 or so, camera at f8. This was shot using those settings: http://cinevate.com/phpBB2/viewtopic.php?t=559 in the brightest setting I believe anyone would encounter.

Kholi, remember that you must baseline your taking lens and camera before you test the adapter...and you must baseline in the 50 IRE area. Your camera's gamma tweaks for knee and stretch will mess with your results otherwise. (check this: http://www.24pdigitalcinema.com/cinegamma.pdf) The curve (referring to waveform monitor rendering of an evenly lit white surface) of an HV20 for example at full zoom is nearly a perfect arc...and this is 100% due to the camera's lens. The XH-A1 however, happens to have a very flat response throughout the zoom range and is so a good condidate for this type of testing.

[Jason Ramsey]

Ok. I attempted my own series of tests similar to what I watched Dennis do in that video. I did a crude version of this last night. Tonight I did a little less crude version, but still pretty crude nonetheless.

First a couple of disclaimers:

I have no real preference of one adapter over the other. I've only ever shot with the Brevis. When I started looking for an adapter on the cheap some months ago to start learning I came across a Brevis on the cheap. I think it started it's days as a beta unit and has been upgraded a couple of times since then. It's a Rev2 now. Doesn't have the latest "MC" (micro collimation) upgrade to it. Anyhow, I found a good deal on an adapter and I bit. It uses CF1L as it's diffuser. This is without the flip module. Beyond that... if I had the money, there's a few adapters out there I would like to buy, each for their own unique traits. So, I happen to own a Brevis, and one single lens... It's NOT a matter of preference of this adapter over that adapter or whatever. Having never had extensive experience with any adapter let alone my limited experience with this one, it would be quite ignorant of me to prefer one over the other... at least in terms of picture quality. Feature set, well that's another matter.

This is not scientific by any means, but I will try to document what I did on my own as much as possible. There will be details I'll leave out for time and boredom's sake, but on request, I may be able to provide some of them.

I've never done this sort of shooting tests and things. I just shoot footage and look at the picture. I don't get all scientific, so this is a first, and I am by no means an experienced "tester" of this sort.

Anyways, I just wanted to try to do something similar to what Dennis did and document my results.

First, I stopped the HVX lens from f4 to f5.6 to f8 to f11. One stop of light, right? I did this with the bare HVX... The only reason I started at f4 was because that was the most open I could be before overexposing the frame with the light I had set up.

As those of you who have read Barry's book or operate with the HVX know, getting exactly 1 stop increments is a bit hard just going off of the lcd readout b/c the HVX actually has 3 ticks of exposure change for every fstop number readout... Meaning in the f5.6 range, there is actually three subtle exposure changes before it will change to the next fstop range on the HVX.

Anyways, so one stop is not exact, and I allow for a margin for error for that. It was just to get an idea (using the marker function on the HVX) of the IRE change with one stop change in iris. Due to what was stated above, it varied a bit from number to number but a good average IRE change for one stop seemed to be around 20 IRE. That's what Dennis quotes, so that's what I figured as "close enough".

I also panned across the page and noted the IRE change in the LCD readout of the HVX from center of paper (I was filming a white piece of paper) to the edges of the paper. My reasoning behind this was just to get an idea of how uneven the lighting on the page may have been so I could take that into account when looking at the waveform in EDIUS later. The difference was that the center of the page was about 2-3 IRE brighter than one edge, and maybe 3-4 IRE on the other edge... More on this later....

But, that's basically my starting point. Approximately 20 IRE seemed to be about the equivalent of 1 stop of light, and a variance of 2-4 IRE across the page in light as I panned across the page checking for changes in IRE.

So....

HVX @ f5.6 gives me a reading of around 74 IRE at center of page. (Note: I took exact X,Y coordinates and noted the IRE for the center of page and corners of the page in EDIUS' waveform. I did this both with the bare lens and the adapter on. Can post those numbers later if requested).

Anywho... Bare HVX @5.6 gives about a 74 IRE at center of page...
Attach the Brevis and a 50mm f1.4 @ f1.4 and I get about 57-58 IRE at the exact same coordinates.

(it should be noted that there is a margin for error of about + or - 1.5 IRE when footage is being played back. One would assume, grain pattern or whatever. This is evident in both the bare lens and the brevis attached numbers. So keep that in mind).

Anyways... f 1.4 is one stop of light, is that right?

I am showing approximately one stop of light loss from bare HVX @ 5.6 vs HVX @5.6 with Brevis attached and 50mm lens at 1.4.

Kinda peculiar to me. Should be a bit more. I would think. One thing I would like to make note of here though, is: Apparently changing your focus will effect the IRE readout. I was at about MF09 with the Brevis attached. Without it I went to something around MF26... don't really remember. But, I did notice that as I changed to focus of the HVX lens after taking the Brevis off, the IRE readout on the LCD of my HVX began to change as well... I don't know remember which way it went, b/c I didn't think much of it at the time. But, it is worth noting that it did change, and that could account for some discrepency... I mean, if it became 10 IRE darker as I changed focus, then that could amount for the missing .5 stops that should be showing from the Brevis' light loss... I don't remember how much or which way the IRE went, but it changed when I changed focus on the HVX lens. Worth noting.

The Brevis with no lens shows about a 10 IRE difference from the bare HVX, so one would think that a lens losing a stop of light, an adapter losing a half a stop would amount to 1.5 stops. I never gave this much thought until when I just looked at it on the waveform (again, I'm inexperienced at this kind of thing). But, I'm showing about a 20 IRE difference taking into account margin for error, etc. with the brevis and lens attached from the bare HVX.

Ok...
So, as I stop through the fstop increments (correct me if I am wrong but these are all one stop of light increments, same as what I did with the bare HVX) on the 50mm lens here's what I see in IRE change...

From F1.4 to F2.0 = Zero change.
From F2.0 to F2.8 = Approximately 1 IRE change
From F2.8 to F4.0 = About 4 IRE change.

If I have a clue what I'm talking about, F1.4 to F4.0 would be 3 stops of light, correct? I'm showing only about 7 IRE at this point... taking into account margin for error, etc... maybe half a stop or so. Continuing on...

From F4.0 to F5.6 = about 7 IRE change. So, this would be about the same IRE change going from 4.0 to 5.6 as going from 1.4 to 4.0 was.

From F5.6 to F8.0 About 21 IRE (approximately 1 stop... now it's more in line with 1 stop change in iris = one stop of light lost, as it was with the bare HVX)

From F8.0 to F11 = About 20 IRE
From F11 to F16 = About 19 IRE

Ok, so this is just what I saw, nothing more, nothing less, and by no means scientific.

Next thing is light falloff of the bare HVX vs. the Brevis w/ 50mm lens attached.

First remember what I stated above about there being a 2-4 IRE variance from center of page to edges of page.

The bare HVX shows pretty much an IRE in line with that. It's pretty flat.

The HVX w/ Brevis and lens attached shows a slight curve in addition to the variance. Maybe an addition 3 IRE, maybe 4... it's hard to tell.

I'm pretty much looking at a 2-3 IRE variance from center to one edge with the bare HVX, and about 5 IRE from center to the same edge at the same coordinance with the Brevis and lens attached.

This could be b/c of the diffuser in the brevis, or my lens, or a combination of both, but there is a slight variance that I can't see with my naked eye, but can see on the waveform.

Anyways, I think that pretty much covers it, I guess.

I find this an interesting discussion, and a confusing one, so I thought I might make better sense of it if I tried it myself... I actually learned a bit about how light loss is supposed to function by observing the HVX lens, which only made me confused as to why the same wasn't true when stopping down the 35mm lens... at least until I hit f8 or so, then things matched up what the HVX does.

Anywho... that's what I saw. Take it for a grain of salt, of course.

Now, I seem to remember Lenny stating that the Letus Extreme had a similar effect as what is being talked about here in relation to the Brevis, although not as pronounced... But, the light loss on the Extreme (particularly in the more wide open apertures) was not stop for stop with the Extreme either... IIRC.

later,
Jason

[Barry_Green]

... most fascinating...

I cannot wait to get a firsthand look at this. There has to be some explanation.

The assertion is that you can stop down a lens from f/1.4 to f/5.6 (being that you're transmitting 1/16th as much light) and yet the net effect is to cut the amount of actual light transmission only in half. Surely you can see how that sounds like snake oil, right? Yet the Cinevate movie and Jason are reporting comparable results, without excessive hot-spotting.

Most bizarre. It defies all logic. Well, it can't defy *all* logic, there's just logic applying that we don't have yet... bizarre...

[pureHVX]

Wow, this thread is moving fast. I want to chime in as that owner of both a flipped Brevis and a Canon K-35 zoom, yes you can use them together. In fact (as was described) I could as well with three spacer tubes attached to the non-flipped Brevis, but personally didn't care for the resulting length.

And yes, the combination of the new achromat lens and the longer path resulting from the flip vastly improves upon the non-flipped results. In fact, I can now zoom all the way in on the HVX200 using the flip module. Such a vast improvement is noticeable immediately.

I rented the flip out for Paul Nordin's shoot with cinema primes and the comment from both DPs working it was that it was much better than a non-flipped, and now truly comparable to the P+S Technik in quality of image. Having shot plenty with both, this claim doesn't come lightly.

If Paul doesn't post some of the footage from that shoot soon, I'll have some from a shoot I'm doing Sunday.

Jason

[USLatin]

It is reacting to the size of the iris and the angle at which the light from that iris hits the GG. Its not that hard to visualize how this could happen.
A denser screen scatters light in more directions is my guess, and so it would also scatter light from the more radical directions more to the center as well.

not having read anything past this that I quote:

I am not getting this still... the general angle of the incoming light is perpendicular to the GG, so do you mean the angle at which the light leaves the GG towards the flip and later the camera? But why is it that there is a sudden drop when the size of the image on the GG is constant? I thought there might be a sudden drop in the amount of light captured by the first element but if the projection on the GG remains of equal size at all times then that doesn't make sense...

What angle is it you are talking about?

[Dennis Wood]

Jason, those numbers are pretty consistent with our findings. In the test we did today, the Brevis with CF1Le and the 50mm lens at f1.4 lost about half the amount of light that we observed while stopping the bare camera down from f2.8 to f4.0 (1 stop). So the entire system loss was just over half a stop.

What you are illustrating though is that quoting light loss without attaching a lens doesn't really tell a potential customer what to expect. Intuitively, affixing a 50mm f1.4 should result in 1 stop of light loss to the system..and it does not. It shows about half of what's expected, and then completely misbehaves by showing 1 stop loss to the camera, as five stops are dialed in on the 50mm! CF1Le was engineered, by the way, specifically to flatten out that curve you were seeing...so my tests will look flatter than yours with CF1L installed. Again, CF2Le and CF3Le do not behave quite this way, and the light loss curve is different. I could have bought a few nice cars with the R&D dollars invested into these little elements :-)

Jason (pureHVX), thanks for piping in here. You're one of the first shooters to have used the flip in the field, and we're hoping the rest of our customers are as happy with the system.

[Jason Ramsey]

All I know is now that I actually have a bit of an understanding about how things "should" behave in regards to light loss after doing that test, I'm more confused than ever :beer:

It doesn't make sense... so someone needs to find whatever the logical explanation to it is.

Later,
Jason

[pureHVX]

Yes ... as if this thread is going around enough, let's have two different Jasons chime in simultaneously.

Jason M ...

[StMad]

Kholi, quicktime, for sure. Quick and dirty...

http://www.conceptsmith.com.au/brevis.mov


I love the SGpro's bokeh, and I love the idea that the Brevis is more sensitive with 35mm lens (my 50mm anyway) at f4 than the SG with lens wide open. I'm keeping both, but man this is an expensive game.

[USLatin]

Dennis... Barry... Tim Michael Jason... crap! all of you guys that know WAY more than me 'bout cameras... the list is just too dang big :)

Guys... IF, and that's unfortunately a bigger if than I'd like... but IF I can get the Nikon 28-70 and 80-200 2.8's... should I? Cause if 2.8 is the same as 1.4 well then HECK, the zooms are said to be sharper than Nikon primes!

I just looked at the 720 from the flipped Brevis, and besides some minor but present hot-spotting I was quite pleased... I would like to see a bit more definition from time to time but it is most definitely a nice image... and I was already I was planning on getting the RedRock mattebox with a (half a built in) ND and a polarizer... but would that be enough to control the light? on a frozen snowed-over lake?!? not kiddin' about that, I mean it about the white lake... (Dennis I was SO happy to see your lake footage!)


Also, did you guys just say you could zoom? if so how much cause that would multiply your focal lenghts when using a set of primes.

[Dennis Wood]

Not to worry on the bokeh issue Steve...stay tuned on that one. Us, we deliberately test with cheap ugly zooms (you can get them used for next to nothing)...and they work extremely well. I've got a 28-200mm Canon f3.5 that is very usable, at all points in it's focal range. In fact, I ended using it at 28mm for the falls shots (http://cinevate.com/phpBB2/viewtopic.php?t=1496) in our flipped footage example. Ben Winter shot this very amusing short (http://cinevate.com/phpBB2/viewtopic.php?t=1700) .... with one f3.5 35-105 zoom lens.

[hienle]

OK, this will be unusual post from me, as you have seen we never defend our products, just let the users judge. But I have to jump in to comment on this.

Barry, you don't need to test further, there is no need, as I know exactly what happened. And you would find out exactly the same result if you do the same test on the same GG.

This is the very reason we had to recall about the first20 Extremes when it entered the production version. We mistakenly assembled the test ground glass (the see through ground glass) to the Extremes. With that ground glass, you would see the same phenomenon. I hope Dennis didn't ship a lot of these GG already.

Here is the way you can prove it, if you have time, of course:

1. Take a piece of glass about 1-2mm thick
2. cut it to the size of the GG holder
3. use the sand to hand sand it, just a little, and let all the aerial images to pass through
4. Put it on your adapter (replace the current GG of course)
5. Do the same test like in the video, you'll see it perform "better" than the demonstration in the video.

The problem? You just let the whole aerial images to pass through the GG and this is the worse thing that a 35mm adapter can do.

OK you have just tested the one extreme of the GG.

Now do the test again, but this time, sand the GG really well (or get the piece of GG from Flip Enhanced or SG Pro or Extreme, they are about the same see through level, which is almost none). Do the same test again. Uh oh, I cannot get that "cool feature". But this is what you want for a 35mm adapter.

I hope this will put to rest this phenomenon as it is a known thing. All DIY adapter builders out there should experience the same thing.

Please do not email me regarding this until you do the steps above. Have fun disproving me ;)

[Dennis Wood]

Well, CF1Le, CF1L or CF1 can be found in every one of our units sold worldwide over the last 18 months. We've not had a single complaint of aerial image pass-thru...and they all perform much the same as this one. I've made it very clear that CF2/Le and CF3/Le have a different response curves and bokeh rendering. CF1Le is purpose designed for maximum light efficiency. The "e" versions that we're currently shipping have been carefully engineered to replicate that very flat response you see as we stop the 35mm lens down...and this is consistent across the line.

In our extensive testing comparing shots using actual film vs. the same lens on the Brevis adapter, we also developed a very accurate matrix of the relative differences in bokeh rendering across the f-stop range...and from this first study evolved our entire imaging element line.

[USLatin]

defend? who's attacking?

who is this?

anywho... I find that that is a cool thing about the GG that let's lots of light get though... better yet I find it is excellent that you can replace the GG's...

I would love to get a third party like Barry to tell me what the pitfalls of the Brevis are as he will most likely do it objectively and in POLITE fashion... also I pray he tells me how to get the best out of a Brevis because if it seems simple enough for full days I will likely go with it

I am not 100% about this but it seems that so long as you know how to avoid hot-spotting and you are pleased with the image then the Brevis with CF1Le allows you to manipulate your DoF to great extent without affecting exposure and it might allow for 2.8 glass to be used as if it were faster...

please, PLEASE do tell me if there is something bad about light getting straight through the glass... I SURE do need help from people that know far more than me... without a DP I would be, well.. a bit worried... I'd be just fine, but I am the first to admit that I am not a cinematographer... so please tell me about things I don't know, but do so objectively and for the good of ALL users

[Michael Friedman]

Can someone explain what 'aerial image pass-thru' is and why it is (or isn't) bad?

I found this (http://en.wikipedia.org/wiki/Aerial_image) but I am not clear how it applies to adapters.

[USLatin]

I guess it is light that passes straight though the GG

And wouldn't it be guided properly by the lenses, I mean it is correctly directed by the elements of the first lens, and you are only recording the correct sector of the GG, so if you can get enough grain and DoF accent (and all other attributes being sought) from a lower amount of grain then so be it... right??

[Kholi]

Yeah, I can in one term: Hot Spot.

The ground glass is basically see through, and you need an actual screen to retain the image, right? If you barely have a screen to project the image, the rest of the image passes through and all of the light is hitting the iris in the first place.

That's why Phillip managed to stop down a Vibrating GG adapter to F8 and not see any grain... cause there's barely an actual surface that nets enough image to keep it from spilling. I can see a few things wrong with it: Namely the difficulty in controlling color rendition and light in general.

[Dennis Wood]

Unfortunately, there is no perfect adapter. We listen to our customers, and the R&D programs we undertake are based on their requests. It's also true that keeping costs down means that not every feature I'd personally like to see, can be integrated into the system at it's current price point. I suspect that Hienle, and Wayne would say the same thing about their products. You'll also find many folks are understandably biased towards what they've spent their hard earned money on. Barry has his own opinions toward adapters and cameras, based on his own experience with them. Competition is a good thing....and the only danger is being caught standing still. Btw, it is technically impossible for light to pass straight through any of our imaging elements. The waveform monitor performance shows that the Brevis flip (as Barry mentioned) is showing no hot spotting at all. The waveform monitor response is nearly dead flat...and it cannot be more graphically demonstrated. This is a very difficult thing to achieve, which is why you don't see too many test like this. Can I say it again? There are lots of great adapters out there and if you have one of them, worry more about learning their quirks and optimizing your experience with them. I think I've demonstrated that a few minutes with a few basic tools of the trade can be very helpful in understanding the lenses, adapter and camera that you're dealing with.

[USLatin]

but the hot-spot only occurs at a specific aperture... so if you can avoid it and you need to use slower glass then this is the answer, right?

Is the hot-spot not present with the CF3Le?

[Kholi]

Btw, it is technically impossible for light to pass straight through any of our imaging elements.

It was also technically impossible for the Brevis to be brighter until it was explained in a better way.



Can I say it again? There are lots of great adapters out there and if you have one of them, worry more about learning their quirks and optimizing your experience with them. I think I've demonstrated that a few minutes with a few basic tools of the trade can be very helpful in understanding the lenses, adapter and camera that you're dealing with.

You can say it again. There's gonna be drawbacks at the price point. We just wanted to know how the Brevis managed this feat.

[Dennis Wood]

Every lens itself has a degree of edge fall-off as well as "hot spotting" and it gets worse as you get to the wider angle lenses. This behaviour also changes with aperture, and with some lenses, is actually worse when they are used wide open. On a wf monitor, this looks like a gently sloping hill. You are taking what is essentially a circular wave and trying to get it to normalize an a planar surface...which is why lenses have all those elements crammed into them.

The line you're seeing on an evenly lit white board in this test is flat all the way to f5.6. Looking at the aperture at f5.6 it is 25 times smaller (5 squared) with respect to surface area..and this is very difficult for any optical system to deal with. In other words, no adapter can fix this unless it can dynamically and differentially alter it's gain value across the focussing plane. There are a few things I won't discuss about the unit, but I have no problem showing you the manifested behaviour of the system :-)

[Jason Ramsey]

Losing light with adapters is one of the side effects of using adapters. It's a tradeoff. It's a tradeoff in design I would imagine and a tradeoff that the end user would need to consider based on their needs.

Less light loss in an adapter is also likely to be a tradeoff in exchange for a less film like representation due to the less dense diffusion, right? To get a more film accurate bokeh, an adapter would lose more light as a side effect, would it not?

So, it isn't so much a lose the least amount of light is best, or a get the most film like representation is the best.... It depends on what the end user is looking for ultimately. Someone shooting a film under controlled circumstances would probably look for the most film like bokeh, etc, etc. Someone who shoots run n gun style stuff or weddings, or is simply just after the shallower DOF an adapter can offer, might not be as concerned with film like representation, and might just want to get the brightest adapter they can find without too much tradeoff in picture quality. Others might wish to live somewhere in the middle.

The advantage to the end user is that there are some really great options to look at in the adapter world for us. When the Letus Extreme came out, it really upped the game for everyone. Letus went from being an affordable flip option to being a very competitive all around product. And, every adapter maker now offers a flip option of one sort or another, and there are some very good adapters out there now, dollar for dollar. Every one is upping their game.

Depends on what you are after, and just wanted to clarify that light loss is only one factor to consider with adapters. Not the be all end all.

With concern to what this thread has been largely about, which is the non-linear light loss of the Brevis (and possibly other adapters to some extent... I'm sure people will be testing it now), the question is... why is it happening... what are the tradeoff's going to be, and how will they effect the shooter based on their individual needs.

Later,
Jason

[Douglas Villalba]

So far, all the testing and argument for a numbers guy like me only tell me that:

The GG in question is inefficient for fast lenses and the amount of light lost is grater at wide aperture since you don't gain anything by using brighter and usually more expensive lenses.

Assuming that the adaptor looses only 0.5 f, then the ASA raring would be about 200 at f 4.0.
Then at f 2.8 it lost 1 full stop and the ASA rating would be 100.
At f 2.0 it lost another f stop and the ASA rating would be 50,
At f 1.4 the rating would be 25.

Don't take me wrong I think the Brevis is a great adapter. They have as far as I know the only Back Focus adjustment and image centering. I just think that the wide aperture phenomenon is a negative for that particular GG.

I love to have the actual ASA rating as use on that test. I know that most videographers don't have any idea of what this is because you use monitors to determine exposure, but without it you can't compare apples to apples.

[Barry_Green]

Okay, then, key question for Dennis: does this "non-linearity" of f-stop response apply only to the CF1-series screens? If so, that would go a long way towards explaining it, as Hien and Michael have said. If there's less effect the more diffused the ground glass is, that all starts to make a lot more sense.

Thanks to all who have participated in helping us get to the bottom of this, or more towards the bottom of it at least!

[USLatin]

As far as I can remember he said that the other elements have different curves. It sounded like one of them might be a middle ground and the third has direct light basically completely avoided by design... I am not sure at all where they fall but it seems that this is something that the guys at Brevis have been completely aware of from the get go and have been developing the current GGs and are developing up coming GG's with this in mind.

Not knowing much at all about optics and such I did understand the powerfully ability of being able to exchange elements... after all this is where our curves reside together with grain and other added qualities that we are asking for in order to emulate film. It was also evident to me that they were serious and had budgeted for R&D of multiple GG's... I think all is possible... whhhell... maybe not all, I really dunno... but this is the biggest selling point for me still to this day: possibilities

Someone equated the change of the GG to changing film stock... and that's an ability that is (was?) missing when using cameras which cannot emulate film all on their own to that greater degree which we are now used to achieving.

If I end up buying into the Brevis with my little money it will be mainly because I believe they will continue to provide me "new adapters" for only the cost of a different GG.

(and I plan to completely understand how to use, how they work, and how to teach my DP to use one before I buy any) hehe... :thumbsup:

[Dennis Wood]

US, in about a week we'll have our complete 8-part Brevis "Video University" online which will go a very long way in helping you with your quest for knowledge :-)

[USLatin]

I think I have a very good idea of how to perform the initial set up and use the Brevis to get the most out of. I say this based on what I've learned and read about it on this thread mostly. But just like with my HVX, knowing how to use it is not enough. So I will be glad to have the VU available if get a Brevis.
Same goes for photography, and just like with your DOP when you direct, knowing how to make and speak with visuals is not enough. You still want and need a pure breed DOP that you can lean on when you doubt yourself or when you simply ran out... I feel the need to MASTER all that I am responsible for, and as a Producer Director I feel that means knowing 100% about the medium before hand. Not so I can do the job of holding the chisel, but because I feel it is my responsibility to know how and why when you are the sargent and your soldiers are on the trenches. Because if you are asked which way to charge, you HAVE to know.
I becha I could go out today with one all alone and come back with some very compelling footage, but there is a long way to go before I can feel that based on my knowledge I might have gone to film school in the past. It is tough to be self-taught, but not so tough when you have DVXuser in your bookmarks and good threads in your User CP. Thank you guys for allowing me to take part in this discussion. I don't like to read from the sidelines even when I don't have much to add because I feel I can learn much quicker if I put my understanding to the test and under your scrutiny.

[StMad]

The GG in question is inefficient for fast lenses and the amount of light lost is grater at wide aperture since you don't gain anything by using brighter and usually more expensive lenses.

Assuming that the adaptor looses only 0.5 f, then the ASA raring would be about 200 at f 4.0.
Then at f 2.8 it lost 1 full stop and the ASA rating would be 100.
At f 2.0 it lost another f stop and the ASA rating would be 50,
At f 1.4 the rating would be 25.

Don't take me wrong I think the Brevis is a great adapter.

I'm not sure how you got those figures. For arguments sake, if f4 is 200 asa with the Brevis, then f1.4 would be pretty close to 200 asa too. The adapter isn't doing things backwards - you're not losing more light the wider open you are. And the benefit of stopping down is that the 35mm lens will almost always perform better 2 or 3 stops down from wide open (eg, f4 vs f1.4).

If my 50mm is at f4 with the Brevis then theorectically it's performing better than when it's on the SGpro at f1.8, and my Brevis setup is still more sensitive. My early opinion is however that the SGpro is aesthetically more pleasing, so I'd use that when I have plenty of light.

Dennis, I'm interested to hear your developments on the bokeh front, however would a trade off be greater light loss? And I'm not sure I want to be changing out screens - I'm sure many are ok with it but it's not for me.

[Douglas Villalba]

I'm not sure how you got those figures. For arguments sake, if f4 is 200 asa with the Brevis, then f1.4 would be pretty close to 200 asa too. The adapter isn't doing things backwards - you're not losing more light the wider open you are. And the benefit of stopping down is that the 35mm lens will almost always perform better 2 or 3 stops down from wide open (eg, f4 vs f1.4).

If my 50mm is at f4 with the Brevis then theorectically it's performing better than when it's on the SGpro at f1.8, and my Brevis setup is still more sensitive. My early opinion is however that the SGpro is aesthetically more pleasing, so I'd use that when I have plenty of light.
.
You would be correct if when you open from f 4.0 to any other f stop the light would change linearly also.

In the case of this GG you don't see any changes when you open more than f 4.0.

Think about it.
if the SGpro is 1.8 when the Brevis was at f4 in reverse since there is no change when the Brevis is from f 1.4-f 4 the SGpro is still at 1.8

You are no loosing light you are just not taking advantage of a wider lens.

[USLatin]

StMad, about not wanting to exchange the GG. I think you own multiple adapters so this may not apply to you. But for those with very limited budget, I think that a little break to take the Brevis off the adapter and exchange the GG in a place with no air movement other than your air gun might be worth it.

Say I go to Fargo and I film my day exterior stuff on the snow and frozen lake on a sunny day but that same day we shoot into the night with the full moon :) and just a few lights... then maybe I will want something a bit less translucent to start with and change the GG at dinner?

Wouldn't this help me avoid the hot spotting during the day if the first element was a bit more like the G35's M2's and Letu's... then at night using the translucent one help me get the most out of a smaller crew and kit?

[Lenilenapi]

Hey guys, I'm happy to see this discussion has risen beyond - you guys are nuts! that's impossible.... etc etc. It seems that most of you are recognizing the phenomena is real. Thanks at last!

Thanks Jason for a great extremely simple test that revealed what we have been saying for a long time. I never bothered to look at the more closed apertures because I had other stuff to do, but that is very interesting. it would be cool top\ compare a few adapters at different apertures.

A couple of quick thoughts:

1. This is not a hot spot or vignetting - I repeat it is not something that indicates a crappy image from the Brevis. It might be related to vignetting but the image is FINE. I have very rarely seen a professional video camera reproduce a flat field as a flat line on a waveform. There is generally some fall off due to the optics.

2. It is a function of the GG or Diffusion Screen not the Brevis mechanism. The Brevis CF2 & CF3 are more linear than the CF1.

3. This seems most directly related to how dense the diffusion quality of the screen is. More diffuse = more linear. Redrock is very diffuse and more linear than any of the others in my tests.

4. Hold on to your seats fellas. The most interesting thing I noticed was that at least between f1.4 to f2.8 there is also NO DIFFERENCE IN DOF OR SHARPNESS of the 35mm lens. This is why I have always described it as "the adapter doesn't appear to even see the extra light from the wider aperture at all." How this might pertain to more closed apertures is worth testing.

5. You can decribe this phenomena many different way and as a glass half-full or one half-empty. If you want you can even drive yourself nuts trying to compute the ASA changes involved.

However, if you care about speed, the important thing is to realize the Brevis CF1L is clearly faster at 2.8 than the denser adapters, but they begin to catch up with high speed lenses wide open. You can draw your own conclusions for your purposes depending on what lenses you like and what f stop you want to run them at.

I hope that you are all beginning to realize that as Dennis mentioned there is a whole world of unusual optical phenomena that come with these adapters. Some that warrant further discussion include:


A. Why Denser screens seem to produce lower apparent DOF - i.e. Same 35mm lens/ Same f-stop: The denser screen will usually have lower DOF.(When I first mentioned this people also yelled "scientifically impossible etc." but now it seems to be accepted here as a fact.)


B. Why do different screens seem more well suited to tele or wide lenses or to different size video cameras. This is particularely something where Dennis claims he has designed his screens to optimize for different situations. This may get into trade secrets though.

C. Why in the world do higher 35mm apertures or video shuttter speeds produce more "static grain" on the image. I have trouble visualizing this, especially the f-stop thing.

D. What's the deal with so-called corner to corner flat field focusing and its absence most of the time in my experience.
Its the whole sharpness issue altogether. Sharpness and corner to corner sharpness are not neccessairly the same.

E. i have found that the way different screens handle extremely bright objects varies quite a bit, and this is a real difference in the kind fo image you can get from these contraptions. the issue is rarely mentioned here though it can be important I think.
Thanks,

Lenny Levy

[USLatin]

A. do you mean lower as in less pronounced out of focus regions?

Dennis, could you please give me a summary of your available GG's and add to it what you can disclose about those you are planning on releasing, when and what will follow? :-) :)

[Kholi]

Not much left for me in thus thread but I will say: I can't see any advantage to not being able to control your color and contrast, not to mention wild highlights, when shooting in any condition.

[Lenilenapi]

US Latin Content - I'm not sure what " hot spotting" you guys are talking about here. I haven't experienced this as a specific problem withe Brevis CF1L though maybe some have. I have seem some overexposure rendering I don't like in some adapter screens, but it really depends on exactly what kind of highlights you're worried about. I wouldn't call it hot spotting though.

I think one of the big differences between these different screens in addition to speed, is just how much softness you like and what kind of bokeh. None of them are going to screw you.

Certainly you can control contrast and color with any of them, that's a camera function or maybe i don't understand what you mean Kholi.

Lenny Levy

[Dennis Wood]

Douglas and Kholi, you are evidently happy with the adapter you are using, and based on your comments, using the Brevis with CF2Le or CF3Le would conform to your expectations. Until someone posts a test just like the one I did with a few other adapters, what are you basing your light loss and efficiency observations on? Everyone is assuming that the other options have been tested on a waveform monitor like we just did...and I've never seen those tests. Ask a guy like Patrick Moreau at stillmotion.ca (an award winning sponsored Canon Pro who uses no less than 5 Brevis adapters) about CF2Le or CF3Le and he'd reply..."No idea". Why? Because they do a lot of wedding and corporate work where light loss is a huge issue. He therefore has no need for CF2Le or CF3Le in his work.

There is no free lunch with adapters. Based on our testing, we believe that no solution can offer a perfect film match with anwhere under 3-4 stops of light loss. We tested head to head with film to come to this conclusion using the same lens on both adapter and film camera. An adapter that did this would be dismissed as a light hog. What we've done instead is offer interchangeable imaging elements so the light hog and light miser could be the same adapter...and give the shooter the choice. We've taken it to the next level and optimized performance with different cameras in the same package. Again, there is no free lunch with adapters.

Barry Green has stated quite clearly in this thread that the Brevis CF1Le test we did demonstrates virtually no hotspotting and a very flat response. I've tested several cams and found that the XH-A1 is very, very good with respect to even light response with it's bare lens. Research on 50mm lens options would demonstrate that you must baseline the lens by itself when used full aperture. For a person experienced with technical testing of cameras, lenses and maybe adapters, they would find these waveform monitor results surprising. Why? As Lenny explained earlier, few cameras and lenses show a line as flat as the one in our tests when tested in isolation. We've taken a typical camera + typical lens + adapter system and tuned the Brevis system to that response..and this is no small feat.

US, I'd direct you to our website, specifically the online catalog for detailed descriptions. For cams like the HV20 we have CF1, CF2, CF3 and for the larger cams u p to HPX500, we have CF1Le, CF2Le, and CF3Le.

Cheers :-)

[Douglas Villalba]

Douglas and Kholi, you are evidently happy with the adapter you are using, and based on your comments, using the Brevis with CF2Le or CF3Le would conform to your expectations. Until someone posts a test just like the one I did with a few other adapters, what are you basing your light loss and efficiency observations on? Everyone is assuming that the other options have been tested on a waveform monitor like we just did...and I've never seen those tests. Ask a guy like Patrick Moreau at stillmotion.ca (an award winning sponsored Canon Pro who uses no less than 5 Brevis adapters) about CF2Le or CF3Le and he'd reply..."No idea". Why? Because they do a lot of wedding and corporate work where light loss is a huge issue. He therefore has no need for CF2Le or CF3Le in his work. There is no free lunch with adapters. Based on our testing, we believe that no solution can offer a perfect film match with anwhere under 3-4 stops of light loss. We tested head to head with film to come to this conclusion using the same lens on both adapter and film camera. An adapter that did this would be dismissed as a light hog. What we've done instead is offer interchangeable imaging elements so the light hog and light miser could be the same adapter...and give the shooter the choice. We've taken it to the next level and optimized performance with different cameras in the same package. Again, there is no free lunch with adapters.
Barry Green has stated quite clearly in this thread that the Brevis CF1Le test we did demonstrates virtually no hotspotting and a very flat response. I've tested several cams and found that the XH-A1 is very, very good with respect to even light response with it's bare lens. Research on 50mm lens options would demonstrate that you must baseline the lens by itself when used full aperture. For a person experienced with technical testing of cameras, lenses and maybe adapters, they would find these waveform monitor results surprising. Why? As Lenny explained earlier, few cameras and lenses show a line as flat as the one in our tests when tested in isolation. We've taken a typical camera + typical lens + adapter system and tuned the Brevis system to that response..and this is no small feat.
US, I'd direct you to our website, specifically the online catalog for detailed descriptions. For cams like the HV20 we have CF1, CF2, CF3 and for the larger cams u p to HPX500, we have CF1Le, CF2Le, and CF3Le.
Hi Dennis,

You don't have to defend your product with me. I which that my Letus had some of the features that your have. Like I said before I like the back focus and centering adjustments.

What I have problem is the way when you talk about the linearity of the GG in question from f 1.4 to f 4.0.

You ask what I base my test? Simple, you agreed that there is light loss. If you take a light meter and for sake argument at f 4.0 your ASA rating is 200 (200 is just an easy number and since 320 is a common ASA rating with 1/3 CCD HD cameras without an adaptor) and without changing anything but the aperture on your meter your ASA had dropped to 25.

In other words you don't gain anything by using a fast lens.

Let me put it to you this way. If your meter calls for f1.4 and you set your lens at f1.4 you would be under exposing by 3 stops since there is no change from 1.4 - 4.0.

Like you said I don't own the Brevis so I can't make a video to show what I am saying.

Why don't you tell us what the ASA rating is at f4.0?

I just had a problem with words that could be misunderstood as the Brevis gaining light instead of loosing just a little light.

I am not being a spokesman for any manufacturer. I paid and own a Letus EX and if Aaron who I bought mine from tell me that you can use speed of over 1/250 sec. or that you could close the lens more than 3 stops and not see noise I would also be speaking my mind.

Just post you ASA with and without the adaptor for us numbers guys.

[Dennis Wood]

Douglas, if you searched back over a year's posts and read all the incredulous responses to the Brevis (using CF1, CF1L, or CF1Le) claims of light efficiency (now demonstrated clearly in the clip) you'd understand the defensive tone :-) It's hard sometimes not to take the grief personally...but the lesson learned is that next time we'll post footage to support these claims. I don't own, use, or test with a light meter as we feel that the waveform monitor and vectorscope readings are much more relevant. The system does not perform according to convention, making a calibrated light meter of questionable value. With regard to light efficiency at wide open apertures, you will find that the same test repeated with any other adapter on the market will show less base efficiency when compared to CF1, CF1L, or CF1Le...I guarantee that.

What we do know is that pretty much every NLE can provide the waveform and vectorscope values, and users can compare/test based on grabs that are analyzed this way, even if they don't have OnLocation etc.
I've been strongly suggesting for a long time that adapters should not be tested without a lens attached as we feel the results can be misleading. HienLe used an equation similar to the following in a discussion on this very forum last year. Assume "x" is the adapter loss.

Total system loss = Adapter loss + 35mm lens loss

Using a 50mm f1.4 lens as the example (the most common 35mm adapter lens?) which has a 1 stop loss at f1.4, and knowing the Brevis flip system in the clip loses .5 stops with a 50mm f1.4 lens affixed:

-0.5 = x (adapter loss) + (-1)

therefore: x = 0.5

In other words, if you use this equation, the Brevis adapter must be represented as a .5 stop gain as a baseline...and we've shown it's not linear at all. That is why I've always rejected quoting adapter loss, and we've always quoted our light loss at .5 stops with a 50mm f1.4 lens attached. I agree completely that it is impossible for any system to create energy passively beyond what is input...and the equation results are misleading. In other words, conventional wisdom does not apply, and the equation needs to more sophisticated to predict light loss in an adapter. A simple graph of the taking lens aperture vs system light loss would work much better IMHO.

[Barry_Green]

Guys, here's the thing -- the Brevis is not behaving according to how we would all expect adapters to behave. That's what led to the aghast reaction to some of these claims.Here's what's going on: hold up a 35mm lens and look through it. Now change the aperture. Does the image through the lens get darker? No. It's supposed to, that's the whole point of having an aperture, but it doesn't. You're looking through the lens and it looks just as bright regardless of aperture.And, are you seeing shallow depth of field? No you're not. Look through that lens and you'll see that everything is in focus.Now, we know that this is indeed "nuts"; stopping down an aperture should produce a loss of light. Stopping down an aperture should produce deeper depth of field. But it doesn't, if you just look through the lens.This is my current theory for what the Brevis is doing. It's using a highly transparent ground glass to just look through the glass, to a degree. Obviously there's some image being trapped there by the ground glass (or else we'd be seeing the image upside down).There are tradeoffs in any situation. There are always going to be drawbacks, there is no "free lunch". So far I haven't spent any time with a Brevis so I don't know what those tradeoffs would be -- I would have guessed that there'd be significant hotspotting, but the waveform doesn't show that, so -- I don't know. It's curious.I'm tempted to say Dennis has created the "pixel shift" of adapters -- whereas pixel shift creates resolution higher than the native pixel count, the Brevis may have created sensitivity. I'm sure there are tradeoffs, but the question is: has the Brevis walked the line fine enough that any tradeoffs just don't matter to most people? If so, well done.

[Dennis Wood]

Barry, if you're interested in playing around with a rig for a few weeks, I'd be happy to send you a full rig/rails in flip/non-flip config with a full set of imaging elements in both the CF, and CFL range :-) Just pm your address/phone number and email, and it'll be there in 2 days.

Cheers :-)

[Douglas Villalba]

You don't understand a simple point. If your system looses as you say 0.5 at f4.0 and you open to f1.4 and still have the same result, what is the use of having a fast lens? It won't even change DOF since the GG only sees f4.0 and up.

You are provably a great engineer, but you need to know some basic laws of photo (light) to see why it helps a DP.

I don't have anything to prove , so if you think that you proved me or Barry wrong with the video. I can't speak for Barry but it just proofed that their is no benefit to using fast lenses with this particular Brevis GG.

We will just agree to disagree.:D

I JUST TAKE TO LONG TO WRITE

[Kholi]

You are provably a great engineer, but you need to know some basic laws of photo (light) to see why it helps a DP.

I don't have anything to prove , so if you think that you proved me or Barry wrong with the video. I can't speak for Barry but it just proofed that their is no benefit to using fast lenses with this particular Brevis GG.

We will just agree to disagree.:D

I JUST TAKE TO LONG TO WRITE


Very good idea to just let people do as they will. We've learned mostly why it happens, when Barry gets his hands on it he'll confirm whether the theoretical cons are accurate or not.

No sense in botherin' about it!

[davide]

I don't have an adapter to test, but I've observed something similar with my pentax dslr.

I shoot a lot with a 50/1.4 Supter Takumar m42 adapted onto my K100d. This lens can be done in either auto-stop down mode (which won't work with adapter) or manual where I close the iris myself. I locked down the shutter speed on the camera and took three successive shots at 1.4, 1.8 and 2.0 with it. The results showed the shots getting progressively darker.

But when I look through the ground glass in the viewfinder as I move the aperture ring from 1.4 to 2.0 I see almost no change in brightness. It's only when I take the pictures and compare them that I see the difference. Note: since the lens is in manual stop-down mode, when I adjust the aperture it actually changes it doesn't stay wide open until just before the shutter is released.

I'm wondering if this is a function of the ground glass in the viewfinder. Maybe it responds to changes in light levels logarithmically while my camera's sensor is linear?

I don't have my lightmeter with me but if I did I'd try holding it in front of the camera and taking a reading and then holding it right where my eye would go behind the viewfinder. It's a kludgy test but I'd turst it more than my eyeballing.

If this is completely wrong I'll edit out my post since the thread is already long and I don't want to fill it up with noise.

If anyone else feels like trying this with more modern lens, try setting a 1.4 lens at 1.8 or 2.0 entering DOF preview mode. The stock ground glass in my k100d offers no discernable change in brightness between these apertures

[USLatin]

Barry, if you're interested in playing around with a rig for a few weeks, I'd be happy to send you a full rig/rails in flip/non-flip config with a full set of imaging elements in both the CF, and CFL range :-) Just pm your address/phone number and email, and it'll be there in 2 days.

Cheers :-)

AHA!!! I think I am sold! ;-)
I was hoping you'd do this... I thought you would as you've shown great faith on your product and openness about it. Now that you did I am only hoping that the tests that Barry performs on the CF3Le shows linear response on par to an M2 or Letus. And that the 1080p image doesn't show too much resolution loss above and beyond other adapters, and all the other quircks and trade-offs are as small as they seem to be on the significantly compressed 720p .mov's I've seen but it seems we are soon to find out.

Barry, please test the Flip. And PLEASE do a shoot-out including LeX and others. Please compare them on all fronts, resolution, edge to edge, and all the other stuffs besides light loss. But I am 200% that your test will be twice as good as I can think of how to test adapters. Please gather a few others before testing! Definitely the top dogs, SGpro and Lex and all the others that may have advantages my humble understanding doesn't discern.

[USLatin]

You don't understand a simple point. If your system looses as you say 0.5 at f4.0 and you open to f1.4 and still have the same result, what is the use of having a fast lens? It won't even change DOF since the GG only sees f4.0 and up.

You are provably a great engineer, but you need to know some basic laws of photo (light) to see why it helps a DP.

I don't have anything to prove , so if you think that you proved me or Barry wrong with the video. I can't speak for Barry but it just proofed that their is no benefit to using fast lenses with this particular Brevis GG.

We will just agree to disagree.:D

I JUST TAKE TO LONG TO WRITE

Douglas, I see your point. If the adapter makes no use of your investment on great glass that's kind of a horrible thing to have happen to you. But don't you think it may be that this adapret allows slower glass to be used instead of not giving you even greater unexpected benefits that you would expect to see on even faster glass?

Also, if it confuses the heck out of you... well this can be far worse than anything an adapter might do to your image cause if it messes at all with your schedule, or even worse with your exposure in a significant way to only find out when watching dailies... well no need to explain how bad that is. But given proper on-set monitoring, or under good lighting conditions, switching to an element that makes the Brevis behave more like a Letus and company should be the way to deal with this.

I don't know much, but I think this might be a way to give a few things up (waiting for Barry's test to find out what) in order to allow people to use slower glass and get the same speed as a fastest adapters out there when using the fastest glass available. I also think that if not already achieved to it's highest expression possible on the CF3Le, then the guys will put out that GG soon enough that will give the best the Brevis will have to offer on the opposite end of the spectrum.

While this may not make the Brevis the best picture in everyones eyes as there are some sick adapters out there producing stunning imagery that the Brevis will likely never be able to reproduce with any GG you drop it... I personally think that the Brevis may not only give me the highest ability to express myself though imagery by providing me with options as some GG's may produce different color and contrast curves when I certainly cannot afford multiple adapters like you guys... but it may also allow me to get unlimited focal lengths with a relatively small investment on 2.8f Nikon zooms... I just have to see how bad the draw backs are at 1080p.

[Dan Vance]

Here's what's going on: hold up a 35mm lens and look through it. Now change the aperture. Does the image through the lens get darker? No. It's supposed to, that's the whole point of having an aperture, but it doesn't. You're looking through the lens and it looks just as bright regardless of aperture.And, are you seeing shallow depth of field? No you're not. Look through that lens and you'll see that everything is in focus.Now, we know that this is indeed "nuts"; stopping down an aperture should produce a loss of light. Stopping down an aperture should produce deeper depth of field. But it doesn't, if you just look through the lens.This is my current theory for what the Brevis is doing. It's using a highly transparent ground glass to just look through the glass, to a degree. Obviously there's some image being trapped there by the ground glass (or else we'd be seeing the image upside down)...


Sorry if this is old info, but this thread is unwieldy...
:)
A diffuser, such as a GG, scatters light--that's how we're able to see an image on it with the camera. But unless diffusion is 100%, some light makes it through the diffuser without being scattered. That's what creates the "hot spot" that is an image of the exit pupil when you look "through" the ground glass. (There are other reasons for the "hot spot," but for adapters, that's the main one.) With a GG, the image is a combination of diffused and direct light. Note that the image of the exit pupil is something that only exists when you look *through* a GG. It's an image that is *created* by the eye (or the imager of the camera with an adapter). Also note that the camera is focused ON the GG, which mitigates the hot spot to an extent, because the image of the exit pupil is not ON the GG, but BEHIND it (within the lens). The location of the exit pupil (lengthwise along the lens) varies with the particular lens, so the intensity of the hot spot varies accordingly. Also its appearance is also going to vary somewhat depending on the F-stop of the CAMERA's lens--the increased DOF of the camera lens at higher f-stops will increase the visibility of the hot spot. And of course the exit pupil gets smaller as you stop down on the TAKING lens.

I think the ratio of diffused to undiffused light (fineness of the GG) can explain at least part of the observation of changing f-stops seemingly without affecting light thruput.

One other thing that is getting in the way in this discussion is the misunderstanding of F#. A lens that is "F1.4" for example, does not "lose one stop." F# is the ratio of focal length to diameter--by definition. If a 50mm lens has a maximum aperture diameter of 35mm, its F# is 50/35 = F1.4. If the lens happened to be made from ND glass and only allowed 10% of light through, its F# would still be 50/35 = F1.4. Same as before. The F# gives an indication of RELATIVE light thruput, but it can't be used to claim any particular light loss. It's useful for relative measurements on the same lens at different F-stops. Other than that, it's not an absolute.

[USLatin]

the increased DOF of the camera lens at higher f-stops will increase the visibility of the hot spot. And of course the exit pupil gets smaller as you stop down on the TAKING lens.

Thank you so much for pointing this out to me. I would have not thought about this if you didn't mentioned it! Thank you! I guess this is because the hot-spot would become more visible with smaller apertures on the camera itself because the image behind the pane on which which we are focused on the GG also comes into focus as the depth of focus becomes greater and then also includes the length of the "opening" though the whole barrel of the taking lens. Did I get that right?


I think the ratio of diffused to undiffused light (fineness of the GG) can explain at least part of the observation of changing f-stops seemingly without affecting light thruput.[/qoute]

Yea, this is what I think Dennis and the guys at Cinevate must have noticed and are now developing multiple GG's to take advantage of multiple points in the curve of this balance.

[QUOTE=Dan Vance;1159388]One other thing that is getting in the way in this discussion is the misunderstanding of F#. A lens that is "F1.4" for example, does not "lose one stop." F# is the ratio of focal length to diameter--by definition. If a 50mm lens has a maximum aperture diameter of 35mm, its F# is 50/35 = F1.4. If the lens happened to be made from ND glass and only allowed 10% of light through, its F# would still be 50/35 = F1.4. Same as before. The F# gives an indication of RELATIVE light thruput, but it can't be used to claim any particular light loss. It's useful for relative measurements on the same lens at different F-stops. Other than that, it's not an absolute.

Thank you for the lesson! This is something I definitely needed to know before I embarked on the treacherous task of purchasing glass without schooling to guide me!

[Lenilenapi]

Davide and Dan Vance's posts above ( especially Davide's observations) I think are capturing the essense of this phenomena.

Some of you guys are right. If you work with a CF1L there is no point in spending extra money on the fastest lenses. Though a fast lens stopped down to f2.8 should perform better than a 2.8 lens wide open at least in theory.

My observations wer that even at 2.8 the Brevis was a bit afster than the others art 1.4 but I'll let you run your own tests.

Dennis, I got to admit the business of rating an adapter without a lens is just c9nfuysing to me and my brain lglasses over reading it. I'll try it again, but I'm leery of theory in general on this and just want to know waht practical tests show. I think you sghould get yourself a lightmeter even if to just understand how the rest of are measuring this.

Comparing the trade-offs of the Brevis to the other adapters should be done with care. there are a lot of variables that affect sharpness and bokeh. Use a FOCUS CHART Please and when looking at bokeh look at overexposed objects at different f stops - a lamp, a window etc, a light bulb - you will see things that could surprise you.

- Lenny

[USLatin]

I am personally hoping that Barry will do a shoot-out instead of just testing the Brevis. Such a test before I got to purchasing my adapter would most definitely be a blessing.

The zooms I am looking at take a significant dive when stopped to 2.8... the differences between the other stops ate not as pronounced.
28-70mm http://www.photozone.de/Reviews/Nikkor%20/%20Nikon%20Lens%20Tests/239-nikkor-af-s-28-70mm-f28-d-if-ed-review--test-report?start=1
80-200mm http://www.photozone.de/Reviews/Nikkor%20/%20Nikon%20Lens%20Tests/46-nikon--nikkor-aps-c/252-nikkor-af-80-200mm-f28d-ed-review--test-report

I already can agree that a better lens will still be better one way or an other... this purchasing glass thing is as complicated as I was hoping it wouldn't be when I first set out to do it myself hehe...

[puredrifting]

I am someone who does shotouts and tests, how much are guys going to pay Barry for his days, possibly weeks of time to do this?

I am all for finding out a lot of these answers but for all of the items you ask for Roberto, this will take Barry a considerable amount of time and effort. Luckily I have a website that pays me to do these, not my regular day rate, but if Barry is doing this for free, we should be thoughtful about bombarding him with requests unless we are willing to pay him for his valuable time.

Knowing how Barry is, he will probably do it anyway but we should not take advantage of his good will.

Dan

[Dennis Wood]

We are expanding our collection of charts etc. with a set from DSC labs...so we'll have some better numbers for you guys based on a few other important considerations shortly. Lenny, we chatted a while ago about light meters, and yes, I should have one...but given where we're going in product development, we'll never use it other than for this application.

In our field tests comparing an identical 50mm f1.4 lens on both film and the Brevis adapter throughout the aperture range, we did see a difference in DOF between f1.4 and f2.8. Being that is what many are using adapters for, the faster lens makes perfect sense...regardless of application. Certainly these lenses are highly recommending for use with our CF2/Le and CF3/Le imaging elements.

[Barry_Green]

Dennis, your offer is very generous and I'd love to take you up on it, but I can't do so for a while, I'm booked solid until February. I'll send a PM with an alternate idea.

US, this is the type of thing I'd like to do -- a complete adapter comparison. But as Dan points out, I do all this stuff outside of my regular jobs (usually to *avoid* doing my regular jobs, heh) so I'm not sure how extensive I could get. In comparing cameras I found that accurately testing one is rational, trying to compare two is exponentially harder, and trying to compare three is astoundingly more difficult. It's not just 3x the work, it's more like 30x the work. Keeping track of every variable and testing for all conditions... it's absolutely intimidating. And heaven forbid that you forget something, because then you invalidate your test results, so all that work for nothing...

But yes, we tried to set up an "adapter shootout" about a year ago, IIRC. And at that time, Dennis was the only manufacturer who responded saying he'd do it. Of course, a shootout of a Brevis against -- nothing else, well, that wouldn't have been much of a shootout, would it? :) So we didn't do it.

It is encouraging to get some progress on understanding these issues. I apologize for using words such as "impossible" before; I should have said "I cannot see how this is possible." That statement would remain true until I was enlightened, at which point we could then say "ah, so THIS is how you're doing it..." Then we can spin down a whole different path of trying to understand the implications of the chosen method.

[marco0782]

If you are someone who likes to shoot f/2.8 for that certain sharpness and depth of field, the Brevis is a LOT faster than the Letus, about two stops faster. That's because shooting with the Brevis at f/1.4 is equivalent to the depth of field on the Letus at f/2.8. The fact that the Brevis has more depth of field than the other adapters gives it this advantage because you don't need to stop down necessarily to make pulling focus easy.


Marco

[Dennis Wood]

Marco, the DOF physically does not change, as that's a function of the lens and circles of confusion etc. What is different is the bokeh rendering/light efficiency and this certainly creates the impression that the DOF of these screens are different.

[Lenilenapi]

Dennis, Thanks for the correction. I have been trying to use the expression "Apparent Depth of Field" for this. For all practical purposes though "ADOF " is all that matters here anyway.

I want to second Barry's explanation of how difficult and painstaking it is to do truly accurate fair tests. I have a lot I'd like to do but I just don't have the time. I never posted stills from the tests I did do because it would have doubled or tripled the amount of work involved. Just didn't have the time.

By the way Barry thanks for the apology. We're all in this together. I've certainly learned much from your painstaking skeptism even if i think you sometimes take it a bit too far.

Lenny

[USLatin]

Pure, I am not asking Barry for anything that he wouldn't want to do and he had already expressed his intention of doing the shoot-out as opposed to just a Brevis test before I repeated myself saying that I would love it if it were in fact a shoot-out.. I have to admit that I do forget or to be more accurate :) don't even GET how hard the test and comparison that HE plans to do will be... hehehe... it is a common phenomena for me to read the title of the test and imagine what I'll find inside but get completely flabbergasted by what I actually find after clicking on it... as I said numerous times I know little about optics and it is hard for me to understand how much goes into it.

But Barry, it is a good point that Pure brings up as I know I wasn't taking "you" for granted but I have not a clue of how much time this would take... or actually I have an idea but I am certain it is nothing but my imagination :) so thanks a million for ANYTHING and thank you regardless, even if you don't , for all the other posts and countless replies to my posts... And again, thanks to ALL of you guys, you included Pure, that know a ton more than me and take the time to answer a little question here and there for me...

[USLatin]

I am a bit lost on how the CF1Le will render the bokeh at 2.8f as opposed to faster lenses. Since my main concern with the HVX was speed I was focusing on image problems to find out if the added speed was in fact a attainable a a low "cost". But I forgot to look at the other factors that should be taken into account when deciding between the zooms and primes.

Being able to use 2.8f zooms with the same sensitivity as the faster primes might be a great thing but what will I give up besides the possible better feel to the focus wheel and possible longer draw on primes such as the all manual Nikons or maybe even Zeiss if I can find them...

[jenningsp]

I am a bit lost on how the CF1Le will render the bokeh at 2.8f as opposed to faster lenses. Since my main concern with the HVX was speed I was focusing on image problems to find out if the added speed was in fact a attainable a a low "cost". But I forgot to look at the other factors that should be taken into account when deciding between the zooms and primes.

Being able to use 2.8f zooms with the same sensitivity as the faster primes might be a great thing but what will I give up besides the possible better feel to the focus wheel and possible longer draw on primes such as the all manual Nikons or maybe even Zeiss if I can find them...


this is just my opinion.... but i think what the brevis "gives up" is the "film look"... yes it has a shallower depth of field and looks better than just the bear camera, but it just doesn't look anywhere near as good as the M2 or the SGpro.
the brevis has amazing technical specs but the footage just doesn't feel right to me. this is including CF3 footage

it's all personal preferences though....

[USLatin]

But what about the possibility of a GG beyond the CF3... what then... cause why wouldn't it be possible for them to make one?

I guess the only fear is that the vibrating GG might not move fast enough for decent shutters with a 100% non translucent GG?

[Douglas Villalba]

the Brevis is a LOT faster than the Letus, about two stops faster.

Marco
Marco your statement is totally baseless. Dennis already answer the DOF statement, so I am only going to answer the above statement.

If this was true the Brevis would be gaining over 1 stop over the camera without any adapter.

Like Barry previously said unless Dennis came up with an innovating new system that actually produces gain rather than light loss, that would be an impossibility.

[Lenilenapi]

Its very hard to put these differences into words and it really does come down to taste and preference. I wouldn' say the CF1L has less "film look" but it is definitely less diffused. That can be good or bad depending on your preference or the nature of the job. You could also describe it as "clean".

I'm using a Pro35mm with an HDCam next week. For my taste the Pro35 is far too diffuse and flares highlights too much. For this job I'd rather have a Brevis CF1L, but it won't work with an HDCam. I prefer the SG for interviews cause I like the soft feeling and lower DOF. For drama I don't know which I prefer - might depend on the shoot. I don't like the CF3L because I can't seem to use my zooms with it and I like the Nikon zoom.

There is a post somewhere of stuff shot for a feature with a Brevis that looks great. I thought the Redrock was too soft and diffuse but I've seen great stuff with that too. The Letus is kind of in between the SG and the Brevis CF1L but there is some highlight handling that's not to my taste - I've been using it though to happy clients.

No simple answer, you can be very happy with any of them.

Lenny Levy

[Dennis Wood]

US, you're an astute fellow. The imaging element R&D program is by no means finished. We're very, very excited about what's to come :-)

[John Alton Disciple]

Speaking of what's to come - how's the 2/3" relay lens setup coming? :happy:

[Kholi]

There is a post somewhere of stuff shot for a feature with a Brevis that looks great. I thought the Redrock was too soft and diffuse but I've seen great stuff with that too. The Letus is kind of in between the SG and the Brevis CF1L but there is some highlight handling that's not to my taste - I've been using it though to happy clients.

No simple answer, you can be very happy with any of them.

Lenny Levy

The feature stuff from the Brevis DID look REALLY nice. I remember that guys post and I did ask him for more footage. Classic case of knowing how to use your equipment and not getting hung up on it (guilty as charged).

To be dead honest, if I had the money I would have an SGpro and LetusEX (speaking at this moment, who knows what'll come out here soon). SGpro for high shutter, high iris scenarios and Letus for everything else.

Or I could just anti up and get a mattebox and some great filters to chop light. =P

[USLatin]

Can someone link me to that footage?

Kholi, out of those options get yourself a matte nice box and filters for sure. Right? I am getting the RedRrock as soon as it it out. (hehehe... if all goes well with the financing, can't forget that)

[Kholi]

Can someone link me to that footage?

Kholi, out of those options get yourself a matte nice box and filters for sure. Right? I am getting the RedRrock as soon as it it out. (hehehe... if all goes well with the financing, can't forget that)

It's always renting, my way. I can see the advantage of purchasing and owning, though, because the gear is universal: it sticks with your camera upgrade regardless. Another good feature of the newer 35mm adapters in that you can strap em on to other cams as well.

I want to wait for the Redrock, I'm sure it'll drop sometime soon.

[USLatin]

Yea, I figured that's why you didn't have it allready.
From what I gathered by e-mailing directly was that they have not had any setbacks (YET) for their Feb release but it is not a hard date by any means.

While we are off-topic... do you have their FF? And does anyone know if it will be the only unit that will work with their remote FF?


About the GG development program Dennis, this is why I asked you about the GG details... really what I was trying to get out of you was more info about the new one you guys are going to release soon. And more spesifically, what I want to know is if this will be a 100% non-translucent? And if it won't be is it because you guys are getting SGpro-like footage with it already? I don't know if that will be possible at all with the Brevis, but you know what I am saying here... talk about it! please :)

[Lenilenapi]

What do you mean by 100% non-translucent?

Someone threw out that word as an explanation of why the exposure issue happens and now it seems its being used to describe the look of an adapter screen. I don't know if this a good choice of words as it implies that there is some light coming right through the screen and screwing with the image. I 've never seen that.

lenny

[USLatin]

That's exactly what it means and what I am saying. This is being extensively discussed on this thread as posibbly the main reason why the Brevis' light loss curve is not linear and as the likely reason for hot-spotting at smaller apertures on the taking lens.

[Lenilenapi]

I'm not going to continue to belabor this any longer , but I have never heard of hot spotting at small apertures being an issue. Somebody here mentioned that , but its far from proven and I have never seen any examples. Maybe I missed them. Nevertheless you can't even use a Brevis at small apertures anyway because you will see static grain. It's a f4 or 5.6 tops unit because its a vibrator.

Did someone post example of Brevis hot spotting? Maybe I'm out to lunch and missing something that's obvious to many of you and if so i'll be glad to eat my words.

In general I find myself defending the Brevis on these pages alot - which is weird because I don't have any special attachment to it. I don't even use it as my primary adapter most of the time.

But it seems to get knocked a lot here and claims are made for other adapters vs. the Brevis that I often find highly questionable. =

Lenny Levy

[Dennis Wood]

John, our 2/3" relay project is going quite well. In fact, the HPX500 should be here this week for testing. This is by far the most I've ever even remotely considered spending on a camera, so anyone in Thunder Bay looking to rent one take note :-)

US, our CINEFUSE R&D program is something we keep a very tight lid on. All I can tell you is that CF1 and CF1Le will continue to be the offerings for maximum light efficiency, and that the next offering is something quite special.

Btw, check this clip (http://www.cinevate.com/phpBB2/viewtopic.php?t=1812)done with CF2Le :-) Ironic, given that the outside temperature is dropping to -32 C here tonight...

[jenningsp]

Dennis, can i suggest an acrylic GG with a grain-less structure. about the same diffusion as CF2 maybe slightly more. it'll be usable at all apertures and can be used static if you're careful to avoid dust.

ay? what do you think? is that what you're working on? :D

[marco0782]

Marco your statement is totally baseless. Dennis already answer the DOF statement, so I am only going to answer the above statement.

Wow, you don't have to be a jerk to disagree with someone or have a discussion.


Like Barry previously said unless Dennis came up with an innovating new system that actually produces gain rather than light loss, that would be an impossibility.

Here are the facts I know, based on shooting 15+ short films and a feature with the Brevis:

1) The Brevis does not handle light loss the same as other adapters; each stop you go down on the lens does not reduce light transmission by equivalent stops
2) The Brevis with CF1 renders less bokeh at f/1.4 than the other adapters, similar to what the Redrock/SGpro/Letus render at f/2.8
3) This means that more appears in focus at a given f-stop than with the other adapters
4) And in conclusion, means that pulling focus is easy when you shoot wide open on the Brevis and therefore stopping down to assist focus pulling is not as necessary as with other adapters

When I shoot with the SGpro I find it necessary to stop down to f/2.8 when I need to make things easier on the focus puller. With the Brevis I could have left it at f/1.4. What this means is that the Brevis, which is already half a stop faster than the SGpro, now has an extra advantage relatively speaking because in the same shooting situation I will lose two extra stops of light in order to get more in focus with the SGpro.

If you don't understand that then you should test both adapters for yourself. It's really upsetting to find myself attacked when I only came on here to share my experiences to those who might find them helpful. And Barry should just put his assumptions on hold until he actually gets to test the Brevis. The characteristics of the way that the Brevis CF1 handles light are different than anything out there and he's just contributing to misinformation and confusion.

[Lenilenapi]

There's a lot to what Marco says. We tend to worship DOF on these pages, but most camera assistents live in fear of wide open apertures for good reason. An SGPro with beautiful bokeh using the SLR size framing, is operating with considerably less DOF than an ordinary feature film. I like the SG for interviews, but the Brevis has much to recommend itself for narrative. I've used it that way. That's when needing less light is more important too.


By the way whether you like the Brevis or not, Dennis has spent an incredible amount of time and money researching diffusing screens. I don't know how he can afford it actually.

Lenny Levy

[Dan Vance]

What do you mean by 100% non-translucent?

Someone threw out that word as an explanation of why the exposure issue happens and now it seems its being used to describe the look of an adapter screen. I don't know if this a good choice of words as it implies that there is some light coming right through the screen and screwing with the image. I 've never seen that.

lenny

The imagers used in all the adapters are "translucent"--that's how they work, so it's really the proper word. And yes, there is light that comes right through, but it doesn't necessarily screw with the image. It's just a fact of the optical system, and it can cause problems under certain conditions. Obviously it's not a big issue, because we see some awesome results from many of the adapters.

[USLatin]

Dennis, that looked nice and sharp... again too bad it wasn't HD, but I saw quite a bit of detail on that other 720 you linked me to earlier. I am pleased with the image but I think I will like CINEFUSE better than CF2/3Le's for some reason... maybe all the mystery :)
I am hoping that the CF1Le and the Cinefuse will constitute the pair I am hoping they will be but I guess the CF2Le or the 3 might be something worth getting as a step in between? I dunno....

I was thinking about this and I thought about using the CF1 for wides and then switching elements (cinefuse?) and re-lighting for close ups, then I can get my gorgeous bokeh when I want it most and and I should have more available as the frame would be tighter... of course this doesn't work for all angles of all locations at all times of the day... but often I should be able to move in and crank up the bokeh... given that they match...

[JasonFox]

US - FYI, the "CF" in CF1, CF2Le, etc. stands for "Cinefuse." :beer: Dennis just has an ongoing R&D program to develop new ones. My CF2Le should arrive today -- can't wait to see how it looks, although work will keep me from it until later tonight.

[Douglas Villalba]

Wow, you don't have to be a jerk to disagree with someone or have a discussion.

Marco I didn't call you any names so you should not feel offended.

If someone is willing to claim something, then they should be ready for someone else to dispute their claim.

I never said that the Brevis was better or worst than any other adaptor including the one I own. People get personally offended when ever someone talks about their product that is not what they expect to hear.

That is why there are still directors that say that they would never use anything but film. Well guess what? Film is good but video has many advantages over film. Sometimes you can use film and some you use video.

The same goes for adaptors. There is not a do it all adaptor. You have to use the right tool for the job. You can claim what ever you want but it has to do what you say it does. Otherwise you are either knowingly or by ignorance, lying.

A 35 mm adaptor is not meant to do TV. It is meant to do film like. That is why it is important for a DP to know how to use meters. How else are you going to know DOP and lighting ratios before the video camera is set up? and, How would he know all theses if (s)he doesn't know the ASA rating of the camera that is being used?

[marco0782]

If someone is willing to claim something, then they should be ready for someone else to dispute their claim.

Certainly, but you are not disputing my claim.


I never said that the Brevis was better or worst than any other adaptor including the one I own. People get personally offended when ever someone talks about their product that is not what they expect to hear.

I didn't say you did, and I didn't say anything of the sort either.


The same goes for adaptors. There is not a do it all adaptor. You have to use the right tool for the job. You can claim what ever you want but it has to do what you say it does. Otherwise you are either knowingly or by ignorance, lying.

I was knowingly illustrating the job for which the Brevis would be the right tool.


A 35 mm adaptor is not meant to do TV. It is meant to do film like. That is why it is important for a DP to know how to use meters. How else are you going to know DOP and lighting ratios before the video camera is set up? and, How would he know all theses if (s)he doesn't know the ASA rating of the camera that is being used?

A 35mm adapter can be used for a variety of reasons. I don't use it because I want to trick people into thinking that my digital footage is actually film. My reasons are:

1) I want the option of shallow depth of field
2) I want to use prime lenses of various focal lengths and from various manufacturers and time periods


If the Brevis doesn't treat light the same way as the other adapters that gives it a special advantage in certain circumstances and that is what I was trying to illustrate. I wonder why you haven't yet commented directly on what I said.

I have had terrific results in digital without any need for a light meter. I can see my lighting ratios on the monitor without having to calculate them with a meter. Zebras and waveform monitors make light meters kind of redundant to me.

Once again, I will try to state my point and if you want to discuss it feel free, but it is impossible to have a discussion if you refuse to directly address what I state:

The Brevis lets you shoot wide open where you would need to shoot stopped down on other adapters. This lets you get away with having less light.


Marco

[Kholi]

Can't wait to Barry gets his hands on a unit, that way we can get illustrated examples of the advantage and if it is or not.

[USLatin]

I don't think you need a meter at all if you have a pro HD monitor, but if you want to start creating when the camera is down then a meter can help you do this. However I am not able to spend that money for that benefit and instead I would try to get more lights since I don't have "20 small to medium lights" :)
Using the reflected light meter in the HVX together with zebras can help quite a bit though it would not be the same as a meter. But with zebras and a good monitor I feel you would be at worst in decent shape. If you can use On Location then you are basically solid but that won't be as portable as a meter.
All of these methods are great if you know how to get the best from them. As it was pointed out to me countless times here when I first embarked on this self-taught film school deal I am doing... it is about the operator and not the gear.

Just my 0.02... both of you guys added to the thread so don't argue with each other as you are helping each other analyze something together with everyone else by pointing out everything you see might play a role in this "new" phenomenon. It is good to discuss all sides. I know I am thankful for both your posts. :thumbsup: :thumbsup:

For the sake of picking your adapter... how hard is it to find a set of used Zeiss primes?

[Kholi]

I

For the sake of picking your adapter... how hard is it to find a set of used Zeiss primes?

Not hard at all. The real question is: How expensive. =P

[USLatin]

Well given that I am considering getting the 28-70mm and the 80-200 new, would you say they are in my reach?

[Lenilenapi]

Maybe about $20,000 if you are lucky. That's why people talk about the Nikon's here. There are Nikon/Zeiss lenses out there but they are not the same thing even remotely.

[USLatin]

Is that new? I guess I would only be looking at a set of Nikon primes then?

[Kholi]

Is that new? I guess I would only be looking at a set of Nikon primes then?

He's talking about Zeiss ZF's and Planars. SLR glass. A used set might run you 2k+

[USLatin]

And how impossible are they to come by without any dust or scratches visible on the footage?

[Ted Spencer]

$20K? Wait a second...I'm looking at these three new Zeiss lenses at B&H for my LEX:

-Zeiss Wide Angle 28mm f/2 Distagon T* ZF Manual Focus Lens for Nikon SLR, $984:

http://www.bhphotovideo.com/c/product/524035-REG/Zeiss_1486_409_Wide_Angle_28mm_f_2.html

-Zeiss Normal 50mm f/1.4 ZF Planar T* Manual Focus Lens for Nikon SLR, $492:

http://www.bhphotovideo.com/c/product/441695-REG/Zeiss_1405174_50mm_f_1_4_ZF_Manual.html

-Zeiss Telephoto 85mm f/1.4 ZF Planar T* Manual Focus Lens for Nikon SLR, $984:

http://www.bhphotovideo.com/c/product/441700-REG/Zeiss_1405176_85mm_f_1_4_Planar_T_.html

Are these not proper choices? They total $2460. Please enlighten...

Thanks

[philip bloom]

$20K? Wait a second...I'm looking at these three new Zeiss lenses at B&H for my LEX:

-Zeiss Wide Angle 28mm f/2 Distagon T* ZF Manual Focus Lens for Nikon SLR, $984:

http://www.bhphotovideo.com/c/product/524035-REG/Zeiss_1486_409_Wide_Angle_28mm_f_2.html

-Zeiss Normal 50mm f/1.4 ZF Planar T* Manual Focus Lens for Nikon SLR, $492:

http://www.bhphotovideo.com/c/product/441695-REG/Zeiss_1405174_50mm_f_1_4_ZF_Manual.html

-Zeiss Telephoto 85mm f/1.4 ZF Planar T* Manual Focus Lens for Nikon SLR, $984:

http://www.bhphotovideo.com/c/product/441700-REG/Zeiss_1405176_85mm_f_1_4_Planar_T_.html

Are these not proper choices? They total $2460. Please enlighten...

Thanks

as mentioned above these are the Nikon Zeiss lenses. Very nice, but not the Zeiss super speeds that cost a fortune.

[jenningsp]

thoes are Zeiss SLR lenses... they're essentualy the same a Nikkor AIS lenses, maybe a little bit sharper wide open, but essentualy the same.

Zeiss also make cinema lenses. a second hand set of about 5 Zeiss cinema lenses will set you back about 20k.


EDIT: DAMN YOU PHIL!!!!

[Ted Spencer]

I see...I didn't realize that we were talking about Cinema lenses. I'm aware that they're much more expensive. Sorry for the misfire...

[USLatin]

Well I was asking about the Nikon mount lenses, not the SLR's so those are the ones I was asking about Ted.
I do want to have an SLR mount but I am in no rush as I first want to shoot a few shorts with my own lenses to get used to and get the most out of the adapter once I get it.

Is there anything else I should consider? Such as the nicer Nikkors...? Are the good Nikkors only the MF's? Which are the best Nokkors? I am not sure which to look at for pricing as there is a million different Nikkors out there...

[Dennis Wood]

Marco, thanks for raising those points. It's absolutely true that CF1/Le have a characteristic "profile" that shooters need to well aware of, as do CF2Le, and CF3Le. Barry has arranged for a technical review, and we'll be augmenting that with a light loss profile for each imaging element.

Because they do not behave at all given the expected shutter speed/aperture ratios, an XY plot of light loss vs taking lens aperture is the only to predict their performance with a given lens. We've invested in a rear-illuminated box, and chart series from DSC labs. so we'll attempt to quantify the behaviour as thoroughly as practical. There's been quite a few discussions on dynamic range compression with adapters, so expect some interesting analysis of that area in short order.

Cheers :-)

[USLatin]

Dennis, so will this be something that Barry will do or what you guys will do separate from Barry's review?

[Douglas Villalba]

I wasn't going to answer 'cause I don't think that there is a worst blind than the one that doesn't want to see.

But by popular demand, here it goes.

Wow, you don't have to be a jerk to disagree with someone or have a discussion.



Here are the facts I know, based on shooting 15+ short films and a feature with the Brevis:
That is nice. I love to see them on my free time. Is there a link to them? or maybe I can rent them at Block Busters.

1) The Brevis does not handle light loss the same as other adapters; each stop you go down on the lens does not reduce light transmission by equivalent stops
Is the glass half full or half empty.

If you start at f16 and you start opening a stop at the time you do see a linear increase in light. When you reach f4 you stop having more light coming in. That is the only comment I had about the Brevis. "A fast lens is useless if you need more light"

I would expect you to agree with that 'cause you just said the same thing but backward.

2) The Brevis with CF1 renders less bokeh at f/1.4 than the other adapters, similar to what the Redrock/SGpro/Letus render at f/2.8
3) This means that more appears in focus at a given f-stop than with the other adapters
4) And in conclusion, means that pulling focus is easy when you shoot wide open on the Brevis and therefore stopping down to assist focus pulling is not as necessary as with other adapters

When I shoot with the SGpro I find it necessary to stop down to f/2.8 when I need to make things easier on the focus puller. With the Brevis I could have left it at f/1.4. What this means is that the Brevis, which is already half a stop faster than the SGpro, now has an extra advantage relatively speaking because in the same shooting situation I will lose two extra stops of light in order to get more in focus with the SGpro.
I assume that you tested those adaptors. I didn't so I'll take your word for it.

If you don't understand that then you should test both adapters for yourself. It's really upsetting to find myself attacked when I only came on here to share my experiences to those who might find them helpful. And Barry should just put his assumptions on hold until he actually gets to test the Brevis. The characteristics of the way that the Brevis CF1 handles light are different than anything out there and he's just contributing to misinformation and confusion.
My friend if you can't handle the heat get out of the kitchen.

I am not going to defend Barry here. He can do that himself. I am just going to answer you comment about assumptions.

Neither you nor Dennis are able to give a scientific answer to the phenomenon. So your quotes are assumptions and I don't see anyone telling you to stop making them.

Don't take it personal.

It has been made obvious to me that there are all levels of expertise and different uses for the adaptors. Not all of you need to use a meter, but wouldn't it be nice to know how to use it? That way most would understand what I have said since the beginning of this thread.

I have been in photography (painting with light) for 30 years and I have teached classes on using and measuring lights to professional photographers. I really don't care if you think I am a jerk. I just hope that everyone reading this can take something useful home.

[Lenilenapi]

I would dearly like to see a more professional and respectful tone on this forum, and particularely this thread. Please think twice about how you phrase things before hitting the send button.


Lenny Levy

[Jason Ramsey]

On topic or don't post. Take your personal disputes to the pm and stop peeing in the pool please... Thanks :)

Later,
Jason

[USLatin]

Hey Doug, do you believe that a translucent GG, as Dennis said the CF1 is, would allow more light to get through than non-translucent GG's and therefor plain and simply allow more light in? I don't now how to calculate ISO to set a light meter myself but this isn't necessarily about how to measure the light but about how much light gets to the sensor regardless of how you measure it. It has not been proven that other adapter GG's are not at all translucent though... :undecided

I have not yet seen two adapters being tested with any other methods, or with a light meter, so I am not personally ready to accept that the Brevis is in fact faster than even the Letus. However, it does seem there are a lot of people --who don't even know each other-- saying it might in fact be faster than all others. And another thing that I am noticing is that there isn't anyone coming forth to clearly stating the opposite. I have not yet seen anyone saying the Letus is being faster than the Brevis... so I think we have covered all areas of the matter as much as they could be before someone does a shoot-out or dissects adapters to find the magic star dust that's adding light hehehe... hahah... which would clearly be cheating Dennis! :)

I think if I get it anyone can so let me re-cap:
_ It seems most people might agree that the Brevis is faster but it has not yet been proven by a shoot-out!
_ It also seems that the Brevis might NEED the flip or a spacer and/or? achromat to avoid soft edges.
_ It also seems the Letus is a superb, solid, high-shutter and extremely fast performer out of the box.
_ It seems the SGpro (and possibly the G35?) take the cup when it comes to the bokeh whores... (great technical term Kholi, hope u don't mind me using it)
_ Lastly it seems that the Brevis provides more creative options that may be somewhat but not completely equatable to being able to switch film stock! And it offers more fine tuning abilities for maximize quality with each individual camera and it's manufacturing tolerances.

Did I miss something? I am sure I missed something... but unless someone can test all or some adapters at the same time then I think there is nothing else to be said that all of you guys haven't already said... well how would I know... heheh... but if there is, please say it clearly so we can all understand it, and without picking sides... I doubt there are any clients here that you may want to convince towards your equipment being better, and we are all helping eachother learn and find other ways to do this stuff. If you are posting here then you are all on the same team. I sure need all the help I can get!

[Kholi]

Put a movie projector on a wall. Put a sheet up as the screen. Look at the contrast and how washed out it looks. Why? Because the image is passing through to the next surface, wall, etc.

Now put up a real screen and look at how much better the image looks.

It's not a hard concept to understand. The GG only needs to be transparent enough to let light in, so that the HVX can see it. If it's too transparent, the image passes through and you lose color and contrast.

I mean I'm probably COMPLETELY wrong here.

[USLatin]

No not at all. As usual you point out something relevant and do so clearly! :dankk2:

However I am wondering if taking advantage of multiple points of a ratio between not letting any light or letting lots of light pass through might have more uses than just one ratio... so while the CF1 is NOT going to be the sharpest image, it may have met an imensly useful balance between the two and the CF3 or next Cinefuse might give you the complimentary opposite end.

[marco0782]

That is nice. I love to see them on my free time. Is there a link to them? or maybe I can rent them at Block Busters.

Sure when I get back from Slamdance in Utah where my first short film is playing this week I would be more than happy to send you links to stills/clips from films I've shot.


Marco

[USLatin]

Congrats Marco!

But please let it die out guys...

instead help me with my lens purchase decisions and help me figure out which are the best Nikon primes, something I am sure you both can help me with and something that may play a big factor on which adapter in the event that the CF3 or next GG + flip HD footage isn't as clean as I personally hope and believe it will be.

[marco0782]

What is your budget? I use the following Nikon AIS lenses which are amazing but can be pricey:

20mm f/2.8
28mm f/2.0
35mm f/1.4
50mm f/1.2
85mm f/1.4


These are all very sharp wide open and no soft corners/vignetting to speak of using the SGpro.

[jenningsp]

my soon to become a reality lens set is - all nikon mount

20mm f/1.8 sigma
35mm f/1.4 AI nikkor - i just bought this today!!!!!!
50mm f/1.4 AI nikkor - i might have to settle for the AIS though
85mm f/1.4 AIS nikkor - i can't find the AI version anywhere???

i'm buying them all second hand. i like the AI nikkors better than the AIS just because of the longer focus draw.

[Jason Ramsey]

I'm still trucking along with a single 50mm f1.4 Nikon.... :(

Next on the list is a Nikon 85mm F1.4... woo hoo....

Later,
Jason

[USLatin]

Lenses that fast might negate the need for the CF1... probably not though... I am exited to see some numbers...

...but regardless as it was wisely pointed out earlier on this thread, faster lenses are usually better in all other ways also, not just speed... so I am going to try to get 1.8's at least... hopefully 1.4's

My budget, I am HOPING, will be about anywhere from $1,600 to $2,100...

it is because of this that I am thinking the Nikon 28-70 and 80-200 zooms might be the best way for me to get the most creative potential... I am a BIG fan of LOOONG focal lengths... I have lots of use for their perspective qualities... so that's an other plus as 200mm lenses won't be as fast as the speed that makes prime sets so tempting... and also the ease of production is just a huge factor... add the speed of the CF1 at 2.8f and the sub-par focus rings on these zooms may start to sound a bit more of a necessary burden...???

I looked in B&H and new the 50 and 85 Planar and the 35 Distagon come out to a bit over $2200 without tax and shipping... how much for them used? I mean I ain't no Jason Ramsey that can wrap a blockbuster with one focal length ya know... I am just not that good. MAD props to you for shooting interiors without a wide, I can't wait to see your film.

And what's the difference between the Distagon and the Planar?

Oh! and I have not discounted Nikon primes if they have a nice draw... which should I look at? there is a million

[John Alton Disciple]

John, our 2/3" relay project is going quite well. In fact, the HPX500 should be here this week for testing. This is by far the most I've ever even remotely considered spending on a camera, so anyone in Thunder Bay looking to rent one take note :-)

That's great news. :2vrolijk_08:

So am I correct in inferring that you have a prototype that you'll be testing the HPX-500 with?

Please keep me updated as, of course, there's a project that I'm in need of this system for.

[Dennis Wood]

John, there is a great deal of testing to do, and with the camera's CAC, interesting options may arise :-) This project will be integrated with several other items in the "skunkworks", so all I can promise is good things for B4 camera owners.

[Tim Naylor]

A 35 mm adaptor is not meant to do TV. It is meant to do film like. That is why it is important for a DP to know how to use meters. How else are you going to know DOP and lighting ratios before the video camera is set up? and, How would he know all theses if (s)he doesn't know the ASA rating of the camera that is being used?

The only time I use a light meter these days is when I shoot film. For digital, I don't use them at all. For consistent imagery and matching shots, I find my waveform and a good monitor far more crucial. And now with SD cards, we don't even need to refer to our lighting ratios to match reverses, etc. We can just look at the clip instantly.

Now what I really would like to see is a spot meter that has a histogram readout instead of a stop or a footcandle. In otherwords you set the ASA and turn the stop wheel while watching where the histogram moves within a given lattitude. Perhaps you could even set the lattitude to match you cameras or your film stock. Now that would be truly revolutionary and perhaps possible these days.

Back on topic.

I've owned all three adaptors (SG, Brevis and LE). I still like the SG picture the best. I do want to re-test the Brevis as by all accounts seems to be much improved. I'm re-testing my LE as I have suspicions about edge to edge sharpness. But I also think I may not be zooming in enough.

If you don't shoot with a lot of light, the Brevis maybe the way to go. If you like high stops, photographic bokeh and high shutter speeds, the SG is the one.

[Tim Naylor]

yes the context, professionalism, composition and lighting have a great deal to do with how the image looks. but what I'm talking about goes beyond that.

it's an inherent trait that spinners give the image. there is a quality that i can't quite put my finger on. i'll call it "awesomeness" for now...

different adapters, namely their GG's, give a certain "look" too the image. and for some reason spinning adapters look "awesome" 100% of the time and non-spinners look "awesome" only 50% of the time.
t.

I'm not so sure it's a function of spinning versus vibrating but perhaps the level of diffusion that lends the "awesomeness" you seem so fond of. What I do notice, however, is less random grain from the vibrating GG. The only vibrating GG that doesn't have the grain buzz is the PS, but it cost a bundle. I also don't think they look as good as their first models (which were spinners). I also wonder if light defracts differently from a spinner.

[Lenilenapi]

Once again I agree with Tim completely. By the way i shot with the Pro35 and the HDCAM F900R today and was surprised at how great the Pro35 looked. If I get a chance tomorrow I may bring my Ex and Letus to see how it compares. Don't know if I'll have time though.

[jenningsp]

i said in an earlier post that i'm not sure it is the diffusion. namely because the LetusEX (which is said to be about the same diffusion as the SGpro) and the brevis CF3 (which is verging on M2 diffusion) also exhibit this same lack of awesomeness....

[jenningsp]

also the bokeh on the spinners is always clean and perfect, whereas on the non-spinners you have to stop down to at least 2.8-5.6 to get that same effect. is this to do with diffusion or how the non-spinners are handling light?

[Douglas Villalba]

The only time I use a light meter these days is when I shoot film. For digital, I don't use them at all. For consistent imagery and matching shots, I find my waveform and a good monitor far more crucial. And now with SD cards, we don't even need to refer to our lighting ratios to match reverses, etc. We can just look at the clip instantly.

Now what I really would like to see is a spot meter that has a histogram readout instead of a stop or a footcandle. In otherwords you set the ASA and turn the stop wheel while watching where the histogram moves within a given lattitude. Perhaps you could even set the lattitude to match you cameras or your film stock. Now that would be truly revolutionary and perhaps possible these days.

Back on topic.

I've owned all three adaptors (SG, Brevis and LE). I still like the SG picture the best. I do want to re-test the Brevis as by all accounts seems to be much improved. I'm re-testing my LE as I have suspicions about edge to edge sharpness. But I also think I may not be zooming in enough.

If you don't shoot with a lot of light, the Brevis maybe the way to go. If you like high stops, photographic bokeh and high shutter speeds, the SG is the one.
How are you doing Tim?

I hardly ever use a meter either. If I am building a set while we shoot another in difficult lighting I will.

You don't need a light meter to understand what I've said before.

I base it on what users, Dennis have said and the clip that shows no change from f4 to 1.4.

Again all I have said is that the GG in question make a fast lens useless since it doesn't have a light gain from f4 - f1.4.

The claim is that there is no light loss from 1.4 to 4. I say that there is no light gained from f4 to f1.4

I also disagree with claims that this Brevis GG is from 1 to 2 stops faster than the other adapters. Anyone that has used the LEX knows that the light loss with lens is under 1 stop. Therefor if this GG is 1 to 2 stops faster you are actually gaining light.

Now I ask you since you know the relationship between ASA, shutter speed and f stop. My ASA without the LEX is 320 and with the LEX and Lens it drops to about 200. According to the claim of 1 to 2 stops that would make the Brevis GG from 400 to 800 ASA. If this is true then you are having a light gain.

Your waveform won't read GAIN (as in camera electronic gain). It only shows range from white to black. Your light meter will.

Now Tim, Do you see any flaws in my math?

[John Alton Disciple]

John, there is a great deal of testing to do, and with the camera's CAC, interesting options may arise :-) This project will be integrated with several other items in the "skunkworks", so all I can promise is good things for B4 camera owners.

Excellent Dennis. :thumbsup:

Now my questions is.... Good things when?

[Dennis Wood]

John, as soon as it's ready for prime time, we'll release more news. Right now, it's safe to assume a few months to get to production volumes. It'll take me about that long to stop sobbing over the purchase of a kitted HPX500 :-)

[Lenilenapi]

also the bokeh on the spinners is always clean and perfect, whereas on the non-spinners you have to stop down to at least 2.8-5.6 to get that same effect. is this to do with diffusion or how the non-spinners are handling light?

In my experience this is completely inaccurate. I don't have time or energy to go through what every one has found through testing. But with nonspinners you need to be open generally from 1.4 to 4 and can't stop down beyond 4 or 5.6 depending on the unit & other factors because of static grain. There are no bokeh issue with non spinners that I know of, and spinners can have bokeh problems just as much as non spinners - Redrock has some issues from spinning with bright lights for example.

Douglas, the light meter analogy is inaccurate and inappropriate in my view for a number of reasons that i don't have time for. It gets you into drawing conclusions that just don't apply.

USLatin:
-Letus is not good for high shutter.
-Believe who you want to about speed differences, there have been shoot outs - I did one. If you what to wait for Barry fine but I don't hear him announcing any impending shoot ouut.
-Brevis has no particular problems with especially soft corners according to most users except Kholi. Ask Philip Bloom.This is an issue with all of them. Flip probably does help though.
-I would not use Brevis CF's as something you can change quickly and often on the set like a film stock. But it does give you options.

Lenny Levy

[Tim Naylor]

How are you doing Tim?


Your waveform won't read GAIN (as in camera electronic gain). It only shows range from white to black. Your light meter will.

Now Tim, Do you see any flaws in my math?

You're right. Good math. Didn't read it closely enough. Scientifically impossible to be one-two stops faster than an LE. My old Brevis (sold it a while back) was about 1/2 a stop faster than my SG Pro Rev 3. Not a a scientific analysis though - just from finding myself bringing the lights in or using bigger units. A light meter would definitely tell me how much more FC's I need to achieve a similar stop.

[Kholi]

In my experience this is completely inaccurate. I don't have time or energy to go through what every one has found through testing. But with nonspinners you need to be open generally from 1.4 to 4 and can't stop down beyond 4 or 5.6 depending on the unit & other factors because of static grain. There are no bokeh issue with non spinners that I know of, and spinners can have bokeh problems just as much as non spinners - Redrock has some issues from spinning with bright lights for example.

Douglas, the light meter analogy is inaccurate and inappropriate in my view for a number of reasons that i don't have time for. It gets you into drawing conclusions that just don't apply.

USLatin:
-Letus is not good for high shutter.
-Believe who you want to about speed differences, there have been shoot outs - I did one. If you what to wait for Barry fine but I don't hear him announcing any impending shoot ouut.
-Brevis has no particular problems with especially soft corners according to most users except Kholi. Ask Philip Bloom.This is an issue with all of them. Flip probably does help though.
-I would not use Brevis CF's as something you can change quickly and often on the set like a film stock. But it does give you options.

Lenny Levy

You're wrong about that. I'm just the only one that'll say something. Believe, I've gotten "THANK YOU" PMs a-plenty.

[Douglas Villalba]

In my experience this is completely inaccurate. I don't have time or energy to go through what every one has found through testing.

Douglas, the light meter analogy is inaccurate and inappropriate in my view for a number of reasons that i don't have time for.

Lenny Levy
When ever you find the time and energy, let me know what analogy and why.

[Lenilenapi]

Because the adapters are not linear and they're responses differ in their linearity.speed at one f-stop is different than at another. Read my first posts on this thread.

[sfoster]

All I know is that I get my Brevis flip tomorrow and will be playing like mad with it and looking for all possible advantages.

[USLatin]

Lenilenapoi, thanks for going through my points... I messed up by mixing the Letus with the SGpro which I think is the one ou guys agree is good for high shutter... right?

About the soft edges on the Brevis, this is a known fact... it shows up clearly in many examples till the user zooms in as much as they can and get it under control, or get spacers which seems to help more, or get the flip which might deal with it al together. So if you are saying that this isn't a problem because proper setup makes it minimal, or you consider the spacer as part of the kit as all non-flip users should IMO then I see what you are saying... it is not something you can't "fix" so maybe it shouldn't be attributed to the system with a blanket statement.

I would LOVE it if you could please link me to your shoot-out!!! Please, I have just now started looking into adapters so I am not aware of all important past threads... I simply wasn't looking.

So how hard is changing the GG in the Brevis? I suppose I might see a video tutorial on the "University" as soon as they allow me to take a look even though I haven't purchased a Brevis. What I am hoping to see in your shoot-out is the effect on DoF and bokeh at the smaller apertures at which the Brevis doesn't react normally.


Doug,
I still think you are confusing the claims... nobody has said that the system becomes ultra sensitive at 5.6 and other smaller apertures, but that it doesn't react to the smaller apertures... the ISO doesn't change... that makes no sense... it is more like the iris has no effect (limited) on light loss...

[USLatin]

All I know is that I get my Brevis flip tomorrow and will be playing like mad with it and looking for all possible advantages.

nice! post some pictures and footage please... maybe a shot of something that makes it easy to see the DoF easily where you switch though the apertures and full focus a little at each of them

[JasonFox]

Even though my head hurts from all of this, I'm going to posit the question anyway:

Even if using a fast lens on the Brevis (which I own) doesn't buy you more light at say 1.4 vs. 4, wouldn't you still want to use one if you could so you can control DoF more? Even though you're not apparently seeing an increase in light hitting the GG, aren't you still affecting DoF by altering the SLR lens's iris?

I got my flip yesterday, but couldn't mount it up properly with my Redrock Rails (they're for sale in the marketplace, btw), so I'll see what's what when my Cinevate rails arrive tomorrow.

[USLatin]

Those are exactly my questions... but nobody seems to be able to quantify it... so I am hoping for a better test...

I need to figure that out cause I am basically set on buying myself the zooms and renting primes as needed.

What I don't yet know is if I should go with the Brevis with two GG's for these 2.8 zooms or LeX for simplicity... I do not want to use the CF1Le but it would be nice to have it available for "emergencies"

[JasonFox]

Well, I've got a good 20mm and an 80-200mm zoom, so I'll tell you if either one vignettes with CF2Le.

[USLatin]

Please... thanks. And can you tell me about pulling focus with the 80-200 while you are at it? It sounds like I may be giving up quite a bit of accuracy with the focus pulling too.

Does anyone know of a dust free bag or sorts? I was wondering if like the mag re-loading tents there may be sealed bags with a window that you could run canned air through and then replace GG's... just a thought.. couldn't hurt! :D
Dennis? What do you think? It might be something simple and cheap that may work nicely... ? Just get something that already exhists and modify it with gloves a window, a port for the air can and an escape valve? Just a thought... too complicated?

[Michael Friedman]

Does anyone know of a dust free bag or sorts? I was wondering if like the mag re-loading tents there may be sealed bags with a window that you could run canned air through and then replace GG's... just a thought.. couldn't hurt!

I think when you get to the point of swapping out GG in a change bag, on set, between setups, you are adding a degree of complication that begins to produce diminishing returns for a real low-budget production environment.

With the attention and resources you are talking about putting to that process you might consider just buying another used Brevis tube with your second GG preloaded for the day and swapping out. I just cringe to think of a full set waiting for a DP to light, block and changes GG elements in a change bag between setups. Of course this is a worst case scenario, but not unlikely given the workflow you are describing. You are back to needing film-crew sized camera departments.

I have always imagined the intended use of swappable GG to be - "I am on a night shoot, I am going to put in the most sensitive GG" - not for swapping on a shot by shot basis.

[Douglas Villalba]

That is correct. Lenny is saying that at f2.8, the Brevis is 1 stop faster. That's half the amount of light required :-) The gap widens as you stop down the lens.

I regularly test with inexpensive f3.5 to f4.5 zooms (not everyone has a 20K lens collection at their disposal), and at this aperture, the Brevis is likely between 1.5 and 2 stops faster than everything else out there.


That would defy the laws of physics.
Agree


The fact that the Brevis does not lose light in a linear fashion that corresponds to the taking lens is a well known, commonly observed fact amongst our users. It is very, very hard to believe as you watch an aperture go from f1.4 to f2.0 to f2.8 (50% reduction from f1.4, then 50% area reduction again from f2.0 to f2.8). We are not defying physics here at all...the imaging elemnent is a break in the optical chain. The physics at work at the imaging plane simply do not correspond to conventional thinking regarding aperture and light loss.

Lenny measured the Brevis at just over a stop faster then the Letus EX with the taking lens at f2.8. I can't speak for the Letus, but his findings are absolutely consistent with our own findings here. With the Cinevate flip, the numbers would be closer to .7 stops at f1.4 and virtually the same, .7 stops as the 50mm lens is stopped to f2.8.

Don't take my word for it. Attach a Brevis to any camera and connect it to a waveform monitor. Stop the lens done from f1.4 to f2.8 and you will see exactly what I, and every one of our customers is talking about. Douglas, there is nothing I've said in this thread that any Brevis user could not confirm for themselves in about 10 seconds of testing :-) This is why we really think adapters should be tested for light loss with a standard f1.4 50mm mounted at f1.4, f2.8 and f4.0

Cheers.


Forgive the frustration. Several claims have been made that appear to defy scientific fact -- such as the idea that using an adapter can actually "gain" light.
.


Ok, here it is. Forgive the audio but we fired this together at the end of the day...should be fairly self explanatory. Please right click and "save as". The file is a 35MB quicktime file that runs about eight minutes.

http://www.cinevate.com/images/lightloss.mov

The camera used was the XH-A1, with no presets loaded (default config) with everything set to manual. AGC was off of course. We've tested on 3 different cameras (HV20, XH-A1, XL2) to confirm that when baselined to approx 50 IRE on the waveform monitor, a 1 stop difference (on the camera)corresponds to ~20 IRE on the monitor. We used Adobe OnLocation on the laptop, with output directed via HDMI to the 42" LCD so you could see clearly what was going on.

:-) Does it lose light? Sure. Does it lose what you'd predict based on convention (that doesn't apply here)...absolutely not. Moving from f1.4 to f5.6 on the 50mm lens mounted to the Brevis flip with CF1Le resulted in about the same light loss as stopping the bare camera down 1 stop.


Look guys therte is absolutely nothing in what I have described that defies any laws of physics or optics. Now I do think it has sometimes been described inaccurately as "gaining light" which is I agree is impossible. Dennis may have used that expression at one point and I told him I thought he was describing it backwards.

However related to the greater transmission it seems to not react to the wider f-stop as you go from f 2.8 to f1.4.
At any rate, because it doesn't react to the wide f stops, it loses its speed advantage as we open up to f1.4, because for some reason the denser screens seem to pick up more of the light from the wider apertures.

By the way. I have no experience with any other claims or tests run by Dennis or anyone else on this forum, and I can't get Dennis test to play so a healthy "no comment"from me.

Lenny Levy


Not at all, it's better for the community when you do. But you were being more direct than that and leaving less room.

I did my own test with my Brevis and SGpro with 50mm 1.8 Nikon, recording my HVX's lcd (with zebra) with my HV20. Not a patch on Dennis' test :), but it showed similar results - there was no discernable light loss from f1.8 to f4 (almost certainly less than half a stop). f4 to f5.6 appeared to lose 1 stop. The SGpro's light loss was linear (1 stop seemed to = 1stop).

So if there is no light loss from f1.4 to f4 the reverse can also apply. There is no light gained from f4 to f1.4


I agree completely that it is impossible for any system to create energy passively beyond what is input.


If you are someone who likes to shoot f/2.8 for that certain sharpness and depth of field, the Brevis is a LOT faster than the Letus, about two stops faster. That's because shooting with the Brevis at f/1.4 is equivalent to the depth of field on the Letus at f/2.8. The fact that the Brevis has more depth of field than the other adapters gives it this advantage because you don't need to stop down necessarily to make pulling focus easy.
Marco


Marco, the DOF physically does not change, as that's a function of the lens and circles of confusion etc. What is different is the bokeh rendering/light efficiency and this certainly creates the impression that the DOF of these screens are different.
It has taken me soooo looooong to to research this thread that I forgot what I was looking for. :D

I have to go home. I'll edit when I get home.

[Douglas Villalba]

Doug,
I still think you are confusing the claims... nobody has said that the system becomes ultra sensitive at 5.6 and other smaller apertures, but that it doesn't react to the smaller apertures... the ISO doesn't change... that makes no sense... it is more like the iris has no effect (limited) on light loss...
I knew I forgot to answer what you said.

Here is how it works:

ASA, shutter speed and f stops are in direct relationship.

Lets say that your correct exposure iwith film is

f4 at 1/120 with 400 ASA film If you don't want to shoot at 1/120th you have to:

F5,6 at 1/60th ASA remains 400 , but if you want to still use f4 instead of f5,6 them

f4 at 1/60 but you have to change the film to 200 ASA

There is always a balance a 1 to 1 relationship.

that is why said that if the Brevis with the CF1le GG at:

f4 at 24 fps the effective ASA is 200 then since there is no light or shutter speed change

f 2.8 at 24 fps yields and ASA of 100 at f2 the ASA is 50 and at f1.4 the effective ASA is down to 25.

The other way if you close it from f4 to f5,6 and loose 1 stop you effective ASA rating is at still 400 ASA.

[Michael Friedman]

There is always a balance a 1 to 1 relationship.


That is true in film. Not with all adapters (http://www.dvxuser.com/V6/showpost.php?p=1157689&postcount=64). The 1 to 1 relationship does not account for translucent imaging elements.

[Douglas Villalba]

That is true in film. Not with all adapters (http://www.dvxuser.com/V6/showpost.php?p=1157689&postcount=64). The 1 to 1 relationship does not account for translucent imaging elements.
I wasn't talking about a translucent Imaging Element. The formula doesn't change. It is made for film we just try to adjusted to video. There are to many variables in video that is why there is no ASA (American Association of standards)

We use f stops that's meant for film. They actually start at f1.0 (human eye sight) you multiply by 1.4 to double the amount of light (1.0X1.4=f1.4 1.4X1.4=f1.96 round up to 2X1.4=2.8 and so on) Do we need it for video? No, but it helps for references.

Not knowing effective ASA is just like not having f stops. Imagine all of these thread if instead of f stops we were saying "I open my iris about half a turn and there was no change, that makes my adapter 3 times faster than yours or was that 2 times" The same same goes for ASA. It is a reference number for comparison.

Do you understand the formula? If you do you would agree with what I have said. It is no different than what others have said. The only difference is that I put numbers for reference.

[Michael Friedman]

Do you understand the formula? If you do you would agree with what I have said.

I understand the formula, and I do not agree.

I guess I view the translucency of the GG as a variable that makes determining a fixed ASA at wide apertures hard to determine.

The GG in this case is not a final (static) destination. It is another glass element on the way to the camera's sensors. As an extreme example, what is the ASA of a window?

I see it as an extension of the back of the (35mm) lens which would not have an ASA rating but would instead be measured in light loss -like a lens.

I think that Barry addressed this topic best here (http://www.dvxuser.com/V6/showpost.php?p=1159194&postcount=107).

Perhaps 35 mm adapters are a 'square peg' that are not going to fit conveniently into the 'round hole' of traditional measurements that apply to film and video acquisition formats.

I guess we can agree to disagree.

[Lenilenapi]

Douglas,
I think the quotes you pulled are a good distillation of the exposure argument. I agree with Michael Friedman about ASA however. If you are determined to work with ASA numbers and a meter be my guest. I use ASA in a very general way with video though I might use a meter alot on some shoots.

For me its a waste of time to be as precise as you're doing especially because changes to gamma and black level, can radically change your ASA, and just the fact that video does not respond in a linear way to light ( sahdows and highlights are totally off the linear scale) makes metering only an approximate tool.

But that's just me. Do whatever you want with the Brevis and your meter.

Re changing Brevis glass in the field: Its very easy to introduce dust and time consuming to eliminate it.
My clients are always on my ass about time. I would never consider it. I did consider the idea of having 2 Brevis units, one for speed and greater DOF and one for softer low DOF that needed more light. I ended up with a Brevis and an SGPro for that reason (because I preferred the SG to the Brevis CF3L) When the Letus came out and people raved about, I had to see for myslef.

USLatin,
I can link you to my shoot out results, but there are no stills, just exposure results, no Bokeh, focus or DOF test stills. I have tested most of that stuff but i just don't have time to take a dozen stills , label them organize them & post them on the web. i admire all you guys who do, but I don't really have time to even be writing these posts. I don't even know how to post stills yet.

Re Brevis soft corners - known fact to who? Not to every brevis User, so please don't make blanket statements. Obviously some people have had that problem, but not all. Philip Bloom chimed in here and said he didn't. I don't have that problem any more than I do on my Letus. Much less than I had with a Redrock. That's why I went to a Brevis in the first place. I agree with Papa - soft corners to some extent are inherent in the optics of an adapter. Many factors can make it better or worse.

I'll try to find my original test results.

Lenny Levy

[Douglas Villalba]

I wasn't talking about a translucent Imaging Element. The formula doesn't change. It is made for film we just try to adjusted to video. There are to many variables in video that is why there is no ASA (American Association of standards)

We use f stops that's meant for film....... Do we need it for video? No, but it helps for references.

Not knowing effective ASA is just like not having f stops. Imagine all of these thread if instead of f stops we were saying "I open my iris about half a turn and there was no change, that makes my adapter 3 times faster than yours or was that 2 times" The same same goes for ASA. It is a reference number for comparison.



How are you doing Tim?

I hardly ever use a meter either. If I am building a set while we shoot another in difficult lighting I will.

You don't need a light meter to understand what I've said before.

I base it on what users, Dennis have said and the clip that shows no change from f4 to 1.4.

Again all I have said is that the GG in question make a fast lens useless since it doesn't have a light gain from f4 - f1.4.

The claim is that there is no light loss from 1.4 to 4. I say that there is no light gained from f4 to f1.4

I also disagree with claims that this Brevis GG is from 1 to 2 stops faster than the other adapters. Anyone that has used the LEX knows that the light loss with lens is under 1 stop. Therefor if this GG is 1 to 2 stops faster you are actually gaining light.



I understand the formula, and I do not agree.

I guess I view the translucency of the GG as a variable that makes determining a fixed ASA at wide apertures hard to determine.

The GG in this case is not a final (static) destination. It is another glass element on the way to the camera's sensors. As an extreme example, what is the ASA of a window?

I see it as an extension of the back of the (35mm) lens which would not have an ASA rating but would instead be measured in light loss -like a lens.

I think that Barry addressed this topic best here (http://www.dvxuser.com/V6/showpost.php?p=1159194&postcount=107).

Perhaps 35 mm adapters are a 'square peg' that are not going to fit conveniently into the 'round hole' of traditional measurements that apply to film and video acquisition formats.

I guess we can agree to disagree.

How do you describe the fact that from f4 to f1.4 there is no light improvement?


Douglas,
I think the quotes you pulled are a good distillation of the exposure argument. I agree with Michael Friedman about ASA however. If you are determined to work with ASA numbers and a meter be my guest. I use ASA in a very general way with video though I might use a meter alot on some shoots.

For me its a waste of time to be as precise as you're doing especially because changes to gamma and black level, can radically change your ASA, and just the fact that video does not respond in a linear way to light ( sahdows and highlights are totally off the linear scale) makes metering only an approximate tool.Lenny Levy
I said that previously, but in film there are other factors as well. That is why there is another factor similar to that in video and we call it latitude.

Our minds are wired differently and we rationalize thing differently. I use ASA, f stops and shutter speed. You can use what ever works for you.

How you determine light loss doesn't matter as long as you have some way of measuring so you can compensate for it.

Do you agree that it is useless to use a fast lens as far as lighting?

Do you agree that this GG can not be 1 to 2 stops faster than the LEX?

[Lenilenapi]

How do you describe the fact that from f4 to f1.4 there is no light improvement?
I've done this so many times I can't count it and I'm not going to repeat it again . It is not hard to imagine. Read the begining of this thread I think.




Do you agree that it is useless to use a fast lens as far as lighting?
I agree, and first thought I would sell my fast lenses, but they are generally optically better and I use more than the Brevis. Size of the rear element could effect GG use as well so i stick with them, but not for speed.


Do you agree that this GG can not be 1 to 2 stops faster than the LEX? No it is faster above f2.8 - That's what this whole xxxx thread is about.

I'm out of this thread now. Too much running around in circles. The basic points have been made and I think most people understand this issue better than before.

- Lenny Levy

[USLatin]

Hey guys, thanks to EACH AND ALL of you... especially for those that ran around in circles. Thanks to you guys making your points in a dozen different ways I feel like I am really getting to understanding a lot that I was never taught from not oging to film school.

Doug, thanks for the break down man! Now since as you explained to me the ASA is exact and was designed for film, and as you pointed out it is not exact but just a guide for video with the wacky curves and all the effect that settings have on them are far from linear and can be changed so much so fast that their consistency can also pose a big problem when you know your camera and take advantage of all the tweaking you can do... then... I guess you really know your stuff as you can use all that as a guide... your meter can offer valuable info... but...

would you guys say that the best possible monitor screen WITH a histogram or waveform would be the end of it all for matching lighting shot to shot...? Is there one with a waveform?!?! or a histogram... I sure would love one! I am thinking about getting a 1024-768, 500:1, 8.4" Carrion (http://www.siniarchproductions.com/lsdsgn/carrion-c.htm) (made by Siniarch) which I saw and considered an amazing deal with excellent resolution for focus and great color... but I don't think it offers anything like a histogram... not have I heard of monitors with such features.... wouldn't that be the way to go so you don't have to rely on your eyes?

Then again... play bacl of the clip to match and switching to the live display of the lit shot you are trying to make match should be plenty for a trained eye...


BACK ON TOPIC! :)
I doubt I can consider getting two barrels... having an SGpro might be best if you are going that way... unless Dennis' next Cinefuse blows out minds which it very well could!
I AM a low budget production... most of you guys would wine and complain like my DP does... then again he is trying to develop his reel with me, plus I do all the research do he doesn't have to figure out the camera's and now other optical equipment's limitations and tricks... he shows up, I regurgitate everything you guys teach me and we start messin' till we feel we can squeeze all the gear has to offer... we will also shoot a pair of shorts before we do my feature so it will be trial by fire (but short fire :))

So... what I am saying is: I might HAVE to get different GG's and I might have to switch them several times though a feature... I think it should be better to shoot magic with the CF1Le... yes the DoF won't be as strong and you should be able to shoot a nice part of it on the CF3 or higher... after all if this might end up being your best visuals why not go for broke with the nicest bokeh and DoF... but what about being able to shoot magic for another 10+ minutes ... got your attention now? I dunno... I haven't done my thang with a brevis yet... I dunno what I might do...

But... back to the frequency of GG replacement... you will not shoot weeks of night straight when you have 80% of your crew working for credits... (you guys crinching with disgust yet? :)) I might shoot two three day stretches at night.. I NEED my crew to get as much sun as possible or they'll flick me off and walk out... also I will probably shoot a total of 6 nights... I will have about 5000w of professional lights TOTAL! 1500W of those are soft! my biggest long throw might be a 2500W fresnel (CoolLights.com 575W HMI) I am estatic that my DP said he'll borrow primes, possibly PL's for it even if it is a month long favor he has to pull, but I can't go into pre-production without knowing that I can make it happen on my own, and that includes 2.8f zooms! yes, ouch again... but he said he'd pull all hard shots and that ought to take care of that (minus a few more takes)

I know... you guys don't want to have to think in those terms... it messes with your head... but THAT is why I am thinking about replacing GG's... and the Brevis is just brilliant for letting indies do that...

yes.. indies is a BROAD spectrum.

[Dennis Wood]

This thread definitely wore me out last week :-)

A few updates though that we'll throw up in their own threads:

1. We just screened a beautifully done piece this afternoon. It was shot with both CF1le and CF3Le swapped on set. Cinevate "produced" the piece but basically it was written, directed, and shot by Piotr Skowrownski, a local cinematographer using two HVX200s. I pushed the swapping elements issue specifically as we wanted comparative footage in the same piece. We did this twice, on the kitchen table, with no problems. One thing that came out right away is that in the old apartment it was shot in (3 rooms, 14 hours, 13 volunteers!) light was an issue. Even .5 stops was a big deal. There was basically one circuit that had to power all the lights. Piotr immediately commented on Cf1Le's efficiency, and the extra room he had on the HVX200 to use f4 for max edge to edge sharpness. It was a great experience to see the crew obsess over lights, scrims, gels etc. to craft the image they were looking for. Very inspiring! We'll have the footage up likely Monday once some final color timing and voice over work is done.

2. Piotr and I discussed the light meter issue (he's shot a lot of film) and I was very interested in what he had to say. He suggested that the light meter had more value to him determining relative lighting levels between scenes, and very little with regard to exposure shooting video. That makes sense to me.

2. Our DSC charts and rear illuminated Ambi system arrived today. Expect a chart series comparing the HV20, XH-A1, and HPX500 with respect to adapter performance and dynamic range (percieved) changes. The cost of these items was a slight shock, but regardless, we were very impressed with what came out of the boxes.

[Lenilenapi]

Dennis - I had the same experience shooting a short in a an old apartment with very poor electricity last summer. The speed on the Brevis made it possible. I will post images when I can get that figured out.

Lenny

[USLatin]

Dennis, please post on this thread the links to the thread covering the short and any other threads you might be starting... just asking so I don't miss anything.

[Spinflight]

Just read this post. Quite interesting I must say. I'm with Barry on this one. You can't defy the laws of physics.

This is my take on what I see happening with the Brevis. As you brighten the 35mm lens from f22 to f 4 the Ground glass actually senses the difference in light levels from the aperture and brightens accordingly. beyond f4 the ground glass is at it's maximum level of brightness. That's why you're not seeing much of a change from f4 to wide open. The ground glass illumination is already maxed out so there is no more sensitivity to more light.

Kind of like shooting an indoor scene with a blown out window. You could add twice the amount of light hitting the window but you won't see much of a difference. It's already blown out. The Brevis seems to act the same way. (it's "blown out" by the time it gets to f4.)

So technically and physically, the brevis should be slower than the LEX because it's already maxed out while the LEX continue to get brighter when you open to f1.4

(Of course this is all dependent on how much light there is in the test) I'd bet that if the lights were dimmer, the ground glass would act more linear all the way to wide open since by having less light the ground glass wouldn't have reached it's illumination peak yet.

My two cents anyway.

[Dennis Wood]

Nope. You'd find the response the same at lower light levels..that curve doesn't change. It just shifts up or down. Barry has stated in this thread that he agrees with our findings and has graciously arranged a review by one of the gurus in the industry.

US, I'll definitely throw a link in here when Piotre has finished his final cc tweaks. He's a perfectionist, and I'm not rushing him :-) One of the actors in the piece is actually our own Nick Palinka. Not only does Nick have a university degree in dramatic arts, but he's now a film student. When not in school, he's with us as a specialist in the clean flow room.

[Douglas Villalba]

This Thread sounds like the Bush-Gore elections. Lets have a 20th recount!!!!!!

I am not a betting man, but I bet a lunch that the LEX is faster than the Brevis at f1.4.:happy::happy:

[Lenilenapi]

Well now I see we are getting serious.
hmm wide open, sounds like it could be close. Be specific about your terms.

On an HVX?
academy or full SLR?
Whose tests will you trust?
What if I send screen grabs?

Can I pick my own restaurant? Drinks included?

Lenny

[Dennis Wood]

Douglas, if you have one, scope it up! The Brevis + flip + 50mm f1.4 lens will measure out at .5 to .7 stops of light loss, relative to one stop loss measured on the camera. I wish it was less, but that's where physics gets in the way. Efficiency wide open is great, but from my perspective, unless you own one of the rare lenses that is sharp edge to edge in that mode, efficiency at f2.8 to f5.6 is more of a priority. I rarely, if ever, shoot wide open for that reason.

On our 1 day marathon shoot, Piotre (all on his own, no advice from me) used the HVX locked at f4 and dialled in at least a few stops in on every lens we used. The result is stunningly sharp footage, even on our 42" 1080P panel.

Lenny, I'm still driving a 27 year old VW. Why? Ask DSC labs :-) All of our tests from this point on will be using their rear illuminated Ambi system and a set of OSGs to go with. One of them is their 72db DX1 OSG which measures a 13 step, 12 f-stop range. Expect some eye opening tests :-)

[Douglas Villalba]

How about if we do it in my studio connected to a switcher and viewed on a 42" plasma spitted side by side.

We can always use screen grabs. I promise I won't use my D70 with a 50 mm f 1.2 at 1600 ASA.:happy:

[Lenilenapi]

Well You can test if you you want Douglas, but i have them both here next to me in my office. Can't get to Florida. Actually I don't guarantee that the Brevis Flip will be faster as I haven't tested that.

Dennis - I just realized I don't have a 77 to 72 step down to accomodate the Flip on my EX-1. I do have 77 > 82 then an 82 to 72 step down which will place me a tad further away. Will that make any difference?
Also i posted this question elsewhere - Will the BVrevis Flip on the SGPro need to be a specific distance from the SG ground glass and will that introduce a possible problem?

Lenny Levy

[USLatin]

No, what we should do is make a reality show out of this thread... we'd make millions

[Dennis Wood]

I can guarantee that 99.99% of the world's population has no interest in this thread :-)

Lenny, check your pms.

[Douglas Villalba]

I bet 99% of DVXUser has no interest in this thread. :smile:

99% of the people that have read it don't have any idea what it is all about.:huh:

[Lenilenapi]

Dennis, I don't see a PMS

[USLatin]

Hope you guys didn't think I was serious cause I'd feel offended :)

[Dennis Wood]

No offense here. When you stop laughing at yourself, others tend to do it for you :-)

[JasonFox]

Whatever happened to Barry's test? Or did I miss something in all the screaming? (At home, btw.)

[Arrik]

Shame on you for reviving this thread, Jason! :kali:

[USLatin]

yea, I bet he will never do it now that they are putting out the tutorials.

[Douglas Villalba]

Whatever happened to Barry's test? Or did I miss something in all the screaming? (At home, btw.)

As far as I know no one without a vested interest has test it side by side.

Even if someone had done with 100% certainty both sides will still claim different results.

I offered a simple two identical cameras one with my LEX and Nikon 1.4 and the other with Brevis also with Nikon 1.4. Run them both through my switcher split the image and set the aperture at 1.4

My guess is that the LEX is 2 stops brighter at 1.4 and it will even out at 2.8 or 4.

That seams to me like a simple test.

No one I know owns the Brevis in South Florida so I can't do it on my own.

My offer still stands :happy:

[Lenilenapi]

As far as I know no one without a vested interest has test it side by side.

Douglas,

At the risk of entering the fray here again, I have to say honestly after explaining my tests many times that I find the above comment personally unfair. Are you suggesting that I have a vested interest of some kind?

My partner and I compared 3 units (SG, Brevis, and Letus) as objectively and carefully as I could with absolutely no axe to grind as I owned all 3 and still do own all 3. I explained my results in detail.

I talk to all three manufacturers and respect all of them immensely. I'll be the first to admit that my results haven't always been the same as some other tests but it certainly wasn't because I had an axe to grind. Its hard to do perfect tests and the units themselves might even vary a bit. My Letus apparently had a prism problem, but i have no idea if that affected the results, I tend to doubt if it was extremely significant but it may have had some affect. All in all I think my tests were objective, careful and informative.

I did get into a quite lengthy and spirited defense of the Brevis because I thought it was being unfairly maligned and its optics and speed misunderstood. But if you asked me which was best I'd tell you the same thing I said 6 months ago - all three have their pros and cons. Even which one is fastest isn't a simple answer.

At this point though the advent of flips on all three plus their attempts to tackle the Ex-1 and the announcement of the new Letus just complicates trying to do objective tests more and more and i can't afford them all anymore.

By the way, I could be wrong, but I don't think Barry ever said he intended to do adapter comparisons, that was a fantasy that was started on this forum.


My guess is that the LEX is 2 stops brighter at 1.4 and it will even out at 2.8 or 4.

Incidently my guess is that you are way off. The Letus at f1.4 will be roughly similar to a Brevis at f1.4 or 2.8 ( no difference). At f2.8 the Brevis will be brighter by at least a stop.

Lenny Levy

[Douglas Villalba]

As far as I know no one without a vested interest has test it side by side.
I meant side like with a switcher split screen. Similar to what Dennis did with the Brevis but with both at the same time.


Even if someone had done with 100% certainty both sides will still claim different results.

I am 100% sure of what I claim and you seam to be 100% sure of your test, but we still disagree.

I would love to do the test my self and if I do and come up with the results that I think I would, I don't think that you would agree with my results. That doesn't mean that you are calling me a lier.

[Kholi]

I think it was already established that there's a trade-off for the Brevis' "light efficiency". At the end of the day, just use what you want to use. For those seeking information I'd suggest buying the adapter that behaves in a proper fashion that way you don't have to wonder what might be happening to the image under certain circumstances.

I'm more than happy with the Ultimate and it's linear light performance.

[Tim Naylor]

As far as I know no one without a vested interest has test it side by side.

Even if someone had done with 100% certainty both sides will still claim different results.

I offered a simple two identical cameras one with my LEX and Nikon 1.4 and the other with Brevis also with Nikon 1.4. Run them both through my switcher split the image and set the aperture at 1.4

My guess is that the LEX is 2 stops brighter at 1.4 and it will even out at 2.8 or 4.

That seams to me like a simple test.

No one I know owns the Brevis in South Florida so I can't do it on my own.

My offer still stands :happy:

Use one camera, a greycard and a wave form. One camera eliminates variables. I think Kwan and Beat did some tests with both. Not sure if they did light efficiency tests though.

I think testing wide open holds little value as most lenses suck wide open. I'd be most interested in 2.0-5.6. But primarily 2.8 since that's where a lenses performance really begins to shine. My guess based on my past Brevis and current LEX, is that the Brevis will have about 2/3 stop advantage.

[JasonFox]

Cripes, look what I've done! I just thought Barry was going to do a test to try and explain the Brevis's non-linearity. NOT compare adapters. I have a Brevis, I dig it. But I'm still curious as to the science behind this attribute. (I know Dennis has a video showing it, but I'm sure a non-Cinevate person doing such a study -- especially Barry -- would carry more water with certain individuals.)

Anyway, quit posting. Go shoot something.

[Douglas Villalba]

After I shoot I do some editing.

Have you render a 30 sec. commercial with Motion animations?

What do you want me to do while I render?:thumbsup:

[Arrik]

Cripes, look what I've done! I just thought Barry was going to do a test to try and explain the Brevis's non-linearity. NOT compare adapters. I have a Brevis, I dig it. But I'm still curious as to the science behind this attribute. (I know Dennis has a video showing it, but I'm sure a non-Cinevate person doing such a study -- especially Barry -- would carry more water with certain individuals.)

Anyway, quit posting. Go shoot something.


Shame, shame, shame....

[JasonFox]

After I shoot I do some editing.

Have you render a 30 sec. commercial with Motion animations?

What do you want me to do while I render?:thumbsup:

Hmmm. Perhaps you should stick to in-camera effects.

[Lenilenapi]

Jason,

I'm curious too. I've posted some conjectures but they don't complete the picture. My guess is that Dennis has some proprietary things he does with the screens that change how they handle imaging. Without knowing that, speculation may not get you too far.
It doesn't worry me though as the important thing is how they behave.

Lenny

[davide]

Cripes, look what I've done! I just thought Barry was going to do a test to try and explain the Brevis's non-linearity. NOT compare adapters. I have a Brevis, I dig it. But I'm still curious as to the science behind this attribute. (I know Dennis has a video showing it, but I'm sure a non-Cinevate person doing such a study -- especially Barry -- would carry more water with certain individuals.)

Anyway, quit posting. Go shoot something.


I believe Barry said after having Dennis explain to him the science behind the CF1 diffuser he accepted the fact that's it light response is non-linear, and decided not to do any tests. If I remember correctly Barry's conclusion was that the CF1 diffuser is able to react that way because it doesn't mimic 35mm motion picture depth of field the way the sgpro or letus does. It creates a shallower depth of field but not 35mm motion picture depth of field and bokeh.

Maybe Barry can chime in on this but I'm nearly certain that he went over to Dennis' side and agreed that the CF1 has a non-linear light response. The cost of that non-linearity, he said, is that you are losing the 35mm film-like shallow dof look that you get with the m2, sgpro or letus.

[Jason Ramsey]

Increased light efficiency typically means less "film like" depth of field, and more "film like" depth of field will typically mean less light efficiency. An adapter maker can either push towards one extreme or another, offer multiple options via interchangeable diffusers, or try to find the best balance between the two... But, (at least not yet) you cannot have "perfect filmic dof and bokeh" and only get .5 stops of light loss. The two don't go together.

So, a CF1 equipped Brevis would probably be the most light efficient of the crop of adapters, but at the expense of a less "filmic DOF".

Likewise, (I have never used this) a CF3 is much more dense and loses more light, but possibly with the gain of a more pleasing DOF and bokeh appearance. Or, a Redrock, which probably loses the most light, but generally people say once you get it setup properly produces a very nice bokeh and DOF. The SGPro being a great balance between them (with a leaning towards bokeh rendition), and many people that use it I have often seen refer to how pleasing they think the bokeh and DOF properties are... The Letus Extreme probably leaning slightly more towards the light efficient side of things, but not so much so as a CF1 equipped Brevis. I've never used a Letus extreme yet, but I would think that it might not have entirely, stop-for-stop linear light loss either... I could be wrong, just a guess. I'd also be curious to see if the Redrock has a similar thing going on as the Brevis with regards to non-linear light loss... except in the other direction, being that it's more light hungry. Does it possibly lose more than a stop of light as you stop the lens one stop at a time? And, does this margin increase the further you close the iris? Basically non-linear like the Brevis, but in the opposite way. The brevis loses little to none early on, and by the time you get to the last few stops on the 35mm lens, it's pretty much become stop for stop linear light loss at that point. I wonder how the other adapters all perform in regards to linearity of light loss? I would suspect that they may all exhibit this in some form or another, as it's becoming quite apparent that things that were always "rules" before, are not quite so with 35mm adapters as there are different forces at work.

Anyways... Them's my observations from my little experience with adapters and from general statements I have seen floating around from users of the various adapters.

The thing to keep in mind is what may be a fault to one may not be to another. And, a plus to one person, may be a deal breaker for another.

What you need/want for your uses. Go out and shoot with it :)

In capable hands, I've seen some absolutely stunning footage from any of these 4 adapters with the Letus, Brevis and SGPro producing consistently good results from a wide range of users.

I'm pretty sure I could have closed my eyes and picked any one of those and been pretty happy with it, as I am now with the one that I'm using for the time being... It's not the latest and greatest, but it gets the job done for me, it makes pretty pictures to me (and apparently to others as well) and it performs consistently with little intervention on my part.

Later,
Jason

[Douglas Villalba]

Hmmm. Perhaps you should stick to in-camera effects.

Yeah, that would be nice. Chroma Keying and titles in camera. Maybe I should ask Panasonic for their next update to include it.:undecided

[Adam J McKay]

correct me if im wrong, wouldn't not losing any light when stopping down the lens be a bad thing? I use aperture to control exposure all the time and going from f1.4 to 4 without light loss would do me no good whatsoever other then increasing my depth of field slightly. And as many have mentioned before, there is a level of light loss that would be a good thing, example being if you are shooting 1.4 or even 1.2, that is going to let in alot of light, so an adapter that loses a stop and half of light is almost going to act like suedo nd filter will it not? Allowing you to shoot with a fast aperture and not have to fiddle with on camera f stop and shutter speed nearly as much. I think this is why I am personally drawn to the SGPRO. And for me, this lack of light loss would be a detturent to buying the brevis.

my 2 cents

[Dennis Wood]

This is precisely why you have a choice, and why we're the only company promoting interchangeable imaging elements (six in total). You can easily swap in and out the formula of bokeh and light loss that suits you. In our very first beta testing process it was quickly apparent that there were two camps in the adapter world. One wants light efficiency, and the other wants very shallow DOF. With the Brevis, you've got these covered in one unit, and now with the MP.1's external oscillation adjustment and microprocessor control, we've made it even easier to tune your image.

Don't forget that our imaging element R&D program is in constant forward motion...and the latest drop-in addition will knock your collective socks off...I promise. It won't require you to buy a new adapter either :-)

Btw, the most comprehensive technical review of 35mm adapters ever performed (7 units covered) has been done already by folks who are very good at this type of thing. All I know for sure is that the review is finished, and should be made public very soon. I also know that our light loss observations have been corroborated 100%.

[Lenilenapi]

Jason is I think on the right path here ( as is Dennis who has been talking about this issue for years BTW) . I've tested all 4 of the above adapters as well as the CF1 & CF3 and stated many times on this forum that a good general rule of thumb is that the more efficient a screen is with light the less linear it is at open apertures especially between 1.4 and 2.8. The Brevis in my exoerience doesn't even see light from the wider apertures so its response at f2.8 and f1.4 is the same. A Letus as I recall lost aprox 1 stop between 1.4 and 2.8 and a Redrock almost the full 2 stops. This is in the nature of adapter optics.

There are numerous pros and cons to either style of screen.

I think Davide is correct about where Barry left the issue but I disagreed with Barry and others about whether you can say which is closer to true 35mm DOF. That's not at all established in my view, and to me that expression gets thrown around way too freely.

I think many people find say an SGPro, a Brevis CF3 or even a Redrock prettier and say it feels more filmic. But "Film Feel "or "Film Look" and even Bokeh are not neccessarily the same as DOF. It may actually be the softness that people are responding to.

Does a Redrock or an SGPro have the same DOF as film? Who knows? Nobody on these pages has ever compared them. To do so you would have to compare either video blown to film and projected, or film transferred to video. Either way a pretty expensive test. Perhaps a careful test comparing a depth of field chart to a 35mm adapter would help. In any case whether you use Academy or full 35mm still frame size would also have a huge affect on DOF. And then there is Academy, Super 35, vistavision, panavision 70, anamorphic, cinemascope, 16:9, 2.35: 1, etc, etc, etc and all affect DOF.

My own guess is the contrary of most thinking. I think that probably the Brevis CF-1 screen scatters light the least and thus might be more similar to film in being closer to the strictly optical circles of confusion (the out of focus parts of the image). The denser screens probably diffuse those circles of confusion more through scattering and thus might have less DOF than film. Its just a wild guess though.

Film has both the softness we like in a dense screen and more resolution than any video camera even without an adapter, so you're just not going to get a perfect emulation. Not possible. Many people find an HDCAM with Zeiss digi primes more filmic because of its sharpness and clarity but the DOF is much higher than a Pro35.

In any case I think trying to determine which adapter is closer to true "35mm film" is a bit of a waste of time. They are all alot closer than an untreated 1/3" or 1/2" chip- cameras.

Pick the tool that you like best for whatever you want to achieve, not for its similarity to something it really can't match.

- Lenny Levy

[Barry_Green]

IF I felt like wading back into these waters (and I really don't, seeing as every time I do it seems like a pack of sharks start attacking from whichever adapter happens to be being called into question) but if I was going to do it, I'd use my 35mm movie camera and my M42 lenses, which happen to work on the film camera and on all the adapters, so it'd be the same lenses across the board. I'd test for light efficiency, DOF, bokeh and FOV across the board. And I'd say what the results are. I'd use the same video camera for every test, with the same lens, so the only difference is the adapter. And I wouldn't give a flying fig who disagrees or who gets different results, because the results would be the results. No spin, no bias, just charts and photos of exactly what each unit produces.

That said, that's probably the better part of a week's worth of work to do it right. This is no small task. And my reward would be to be eviscerated by fanboys of some or other adapter, whoever's sacred cow gets gored. And it'd be expensive (film stock and time). And, I don't have all the adapters, I'd have to either buy them or depend on the kindness of DVXUsers to loan 'em.

And even then, the results would stay relevant and accurate only until the next revision by the adapter makers, which (at least in the case of Letus and CineVate) seems to happen monthly!

So, with that said, if you guys want me to do the Adapter Test From Hell, I could maybe get to it in June, but you'd have to get all the adapter makers to agree to send their latest versions 'cause I'm not gonna spend $5,000 to buy 'em all...

[Douglas Villalba]

That is very generous of you Barry. I know that if it was me doing what you are offering to do, it would cost me out of pocket a few thousands of dollars. Even if I didn't have to buy the adapters just in time not producing money.

I don't think you are commended publicly enough for your researches. I want you to know that we really depend on you and few other that do leg work sore of speak, so we know what to expect before buying new technology.

By the way good report on the HVX200a and the upcoming 170.

Thanks

[Lenilenapi]

That said, that's probably the better part of a week's worth of work to do it right. This is no small task.


Yup probably about a week's work. I'm amazed that you are actually offering to do it Barry. I hope no one really expects you to bother.

It would be interesting, but in the end the adapters would be different in weeks and it wouldn't make all that much difference to anyone. These are great tools - there is plenty of information out there already. Use them and make pictures.

Lenny Levy

[USLatin]

Barry if you did it you'd go from celebrity to becoming the Greek God
of film making on a budget... add that to your oder medals... but not expecting to have you do it...

[Kholi]

He's right... there's really no reward in doing that sort of test. Someone's gonna cry, someone's gonna sigh. Might as well just realize what works better for you and figure out how you want an adapter to perform then stick with that.

[Barry_Green]

It would be interesting, but in the end the adapters would be different in weeks and it wouldn't make all that much difference to anyone.
Exactly...

[davide]

Thanks for the offer Barry. If you ever do that test maybe you could place it in an issue of DVXUser Monthly. It'd be sure to attract a huge amount of readers and because of that maybe you guys could negotiate to get more advertising in that issue to make up for the cost of film stock and time.

At the end of the day I don't think people should be choosing adapters based on how 'filmic' they look but based on whether the look they give suits the projects they want to do.

[Dennis Wood]

Actually Hubert's Arri 2C 35mm camera showed up today in fine shape from Holland. So hang on :-) Btw, Barry the overview as you have described has pretty much been done already in what sounds like the most thorough review (free I might add of any outside bias) ever done on 35mm adapters. Doing a thorough review before that "super-review" comes out would be a waste of time.

[Douglas Villalba]

Barry the overview as you have described has pretty much been done already in what sounds like the most thorough review

You care to tell us were it is or when it is coming out.


(free I might add of any outside bias)

All reviews are bias. It is just human nature


ever done on 35mm adapters. Doing a thorough review before that "super-review" comes out would be a waste of time.