Does Letus Extreme lose more light than Brevis

Michael Friedman said:
That is true in film. Not with all adapters. The 1 to 1 relationship does not account for translucent imaging elements.
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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.
 
Douglas Villalba said:
Do you understand the formula? If you do you would agree with what I have said.
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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.

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.
 
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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
 
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Douglas Villalba said:
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.
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Douglas Villalba said:
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.
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Michael Friedman 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.

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

Lenilenapi said:
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
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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?
 
Douglas Villalba said:
How do you describe the fact that from f4 to f1.4 there is no light improvement?
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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.


Douglas Villalba said:
Do you agree that it is useless to use a fast lens as far as lighting?
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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.

Douglas Villalba said:
Do you agree that this GG can not be 1 to 2 stops faster than the LEX?
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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
 
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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 (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.
 
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.
 
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
 
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.
 
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.
 
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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.
 
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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:
 
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
 
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 :-)
 
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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:
 
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
 
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