Does Letus Extreme lose more light than Brevis

[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!
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.

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. The 1 to 1 relationship does not account for translucent imaging elements.