Questions re Letus Ultimate.

Kholi said:
Also, I've never had any other SGPro user report that their adapter didn't respond linearly to light loss. Timur Civan recently, in another thread, said that his SGpro responded linearly to light loss. Are you saying something different?
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the SGpro responds linearly all the way up to f2. the difference between f8 and f5.6 is one stop, the difference between f5.6 and f4 is one stop, the difference between f4 and f2.8 is one stop, the difference between f2.8 and f2 is one stop BUT the difference between f2 and f1.4 is 1/10th of a stop.... and that's only in the center of the image. the edges remain the same....

1/10th of a stop is not what i call significant... it's barley even perceptible unless you flick back from one to the other.

Kholi said:
But how that equates to the Ultimate being "more diffused" than the SGpro is odd. How did you figure that?
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this is where my doubts come from... for the Ultimate to respond linearly all the way up too f1.4 then the GG needs to be more diffused than the SGpro's. because the more diffusion the GG has, the more linear the response.

that's where i'm coming from.
 
We're talking about two completely different subjects, that's the issue. When I think of the "Brevis Effect" I'm thinking of how light transmission from 1.4 to F4 doesn't change. Dennis proved that in his video. I'm not talking about exact measures from 1.4 to 2 or 2 to 2.8 and so on. That's for more qualified people like Leni to judge.

You can't measure 1.4 to 2 without a lightmeter and proper tools, those of which I do not have. When I say it responds linearly I mean when I roll the lens iris light transmission decreases. Unlike the Brevis and that specific diffuser it takes many clicks to see light transmission changing.

I have no idea how much light it loses from 1.4 to 2 exactly. I'll leave that kinda measurement up to someone who needs to know or has the tools to calculate the amount of light being transmitted but does it change from 1.4 to 2? Yes.

Sorry, we're on two different roads here.
 
The so-called "Brevis" effect is called that because we are the only manufacturer so far that took the time to demonstrate with a waveform monitor what actually happens when you stop down the taking lens, and compared that to stopping down the video camera lens. That entire controversy over linearity and 35mm adapters ended with that video. Btw, there is a change from f1.4 to f2.0...just not what you'd expect. The tests we performed take nothing more then an NLE with a waveform monitor. I can tell you with confidence that no adapter claiming .8 stops of light loss has a linear light response from f1.4 to f5.6. It would be incorrect to assume that we've never tested the spinning disc/decoupled condenser model either. None of them came close to the light efficiency we were looking for. That's not a bad thing, just not good for us.

The response changes a fair bit with our different imaging elements CF2Le and CF3Le and the video to show that, as well as the visual differences will be up next week. We repeat our original light loss measurement using CF1Le, CF2Le, and CF3Le in the studio, then take them outside for a side by side comparison. I'm guessing a few more assumptions will fall shortly after it's released. Taking anecdotal comments, and then comparing them as fact to our careful tests doesn't seem appropriate. Duplicating the tests with different systems makes perfect sense and is very simple to do.

For those hung up on the linearity thing, rest assured that the linearity you seek is available using your video camera's aperture :-)
 
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The terminology is being crossed. I thought Leny was asking "Does the light transmission change when you stop down?". That's what I know as the Brevis effect. If he was asking something different then that's a different story.

So here's the question: Is the Ultimate like the Brevis in that when you stop down you don't see much of a difference in transmitted light? No. It responds like how I would expect it to, losing light as you stop the lens down. How much in EXACTS? Well, someone ask Doctor Frankenstein because that's what all of these things are: Frankenstein Contraptions. If it doesn't respond how, say, a RED ONE or FILM CAMERA responds... I guess you know why.

Whether it's "accurate" is not what I'm getting at. Hell, even lens markings on SLR lenses aren't accurate. Some lens manufacturers claim their lenses are 1.8 when they're really 2. Head on over to 16-9.net to see that.

Again, I was responding to the question above, if that was not what was asked then I can't answer it.

Edit here: I'm personally not so hung-up about exacts on light loss transmission i.e does 1.4 to 2 equal 1 stop? As long as it responds significantly enough or close enough to what I would expect that's fine. It's kind-of a moot point because the characteristics of the ground glasses themselves change what DOF characteristics look like, proven once more by Leny and Dennis. So, for me, as long as the amount of light pouring through the lens in increments close to that of the F stop 1/2 or 1/3 or whatever scale I'm fine.

However I AM still hung up on 35mm FOV. :B Hur hur.
 
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thanks dennis. i just think it's important to know exactly where the cut off point for this "brevis effect" is for each of the adapters. because we've got people spending thousands of dollars on f1.4 lenses when they aren't any faster than f2 lenses on the adapter they're using.....


Kholi said:
but does it change from 1.4 to 2? Yes.
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i propose that you'll find the answer is in fact No.
 
I just did it. Does it change in a full stop? I have no idea. But does it change? Absolutely. It's pretty obvious even in the HVX LCD.

Again, let's clarify: Are you saying NO it doesn't change in a full stop or NO it doesn't change at all? Let's get on the right track so we can understand each other.
 
Well I thought this had all been laid to rest, but just to give it one more brief go.

Kholi, Yes we all expect there would be some change, but probably not a full stop.

I believe that Dennis and Jennings are correct that neither an SG nor an Extreme are linear from 1.4 to 2.0. In fact they are probably not even completely perfectly linear from 2.8 to 2. However I get different slightly different results from Dennis and Jennings so its pointless to quibble about details.

However, what started all this was when people started to say a given adapter loses say 1/2 stop of light. I find that is usually a deceptively vague measure.

My tests pointed out that the light loss figure could be markedly different at 1.4 and 2.8. An adapter that was faster or equal at 1.4 could be slower at 2.8 That's why I asked a simple question - how does the Ultimate compare to the Extreme at 1.4 and at 2.8. I know how the Extreme compares to a Brevis and an SG at those f stops from my own tests.

Similarely I'm wondering how the Ultimate screen diffuses the DOF and highlights compared to the Extreme. I also suspect that that is related to lightloss - but Kholi is right - who the hell knows. I don't understand these beats.

Jennings - the best way to measure those figures (unless you have Dennis's rig) is with a light meter. look at my tests - the link is at the beginning of this thread.

Kholi - How can you light without a lightmeter? Do yourself a favor and blow a few dollars on a fundamental tool. Actually I hate to shoot without a waveform also - that;'s why I didn't buy a Carrion monitor.
- Lenny
 
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Kay, I was under the impression that you were asking: Does it respond to stopping down like the Extreme. And again, I'll say, from side by side with the Extreme it looked to respond the exact same way. However, only a scientific test (less by eye and more by charts and graphics and monitors) will say whether or not that's the truth.

Does the adapter lose half a stop of light like manufacturers claim? I know it loses as much light as an Extreme. That's enough for me.

Once more: I do not know if it's 1 stop to 1.4 to 2 and do I care, personally? No. Why? Because it honestly doesn't matter if the measurements are not accurate to what are published standards. You can only hope to get within the range, but it's all pretty much guessing which means I pretty much agree with you, Leny. It's pointless to quibble about how much light is being transmitted and it's just up to the user to decide what's worth it. I see a difference between 1.4 and 2. Is it negligible? Negligible by definition is defined by opinion. I have the choice as well as others do to spend money on faster lenses. Doesn't matter which adapter that they use. I know PLENTY of SGPro users that swear by the fastest lenses that they can obtain and use them wide open when necessary. That's how it is, man.

As far as lighting without a lightmeter goes I have been hacking it: going by what looks right to me and what I'm used to. When there's a monitor with waveform on set or location then I'll use that, other than that Zebras have been working out quite well for me. Bad me.

If it were actually a few dollars I'd get one. :B It's more like hundreds of dollars, though.

Edit: One great thing about using RED is all the waveform and monitoring options (r, g, b channels) that you can employ. On big budget stuff (which I haven't gotten to yet) I'd like to have a Light Meter and all the stuff I SHOULD have... I just haven't seen the immediate need-- yet-- to go out and get one.

I do want a Waveform around, though. THat's why HPX170 is tempting, along with the HD-SDI output.

As far as THIS thread goes and light transmission: I got the question backward. Does the Letus Ultimate see a change in transmitted light between 1.4 to 2 and so on and so forth? YES. Is it linear or accurate? I have NO idea. I just know that it "looks" right at this point.
 
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Oh. Okay. I said that many posts ago. LOL. It was just a confusion of what's being meant and I was on a different page than the rest of ya. Sorry!
 
ok cool. i think we're all an an understanding. :)

just for fun i got out my sgpro and did my own little test to demonstrate what i'm talking about for anyone who's interested.

gx23FxX9-e17d946058f6dc89bde98f30e143287e.jpg

URL: http://www.postimage.org/image.php?v=gx23FxX9
PqNGa70-e17d946058f6dc89bde98f30e143287e.jpg

URL: http://www.postimage.org/image.php?v=PqNGa70
aV1Exzq0-e17d946058f6dc89bde98f30e143287e.jpg

URL: http://www.postimage.org/image.php?v=aV1Exzq0

the second image should be as dark as the third...

there is a difference between 1 and 2 but in my mind it's not enough of a difference to matter. it's only 1/10th of a stop according to my waveform.

i still want to know how the letus performs in this regard :D
 
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Jennings - Its not an accurate comparison to change the f stop on the video camera as that's not precise on a DVX, nor neccessarily even linear ( sorry ) either.
However your point is nevertheless correct and you would find something similar on a an Extreme. - Again look at my tests as they are relatively accurate.

It all old news though. Lets reinvent a different wheel shall we.

This began as a " hey what's the Ultimate screen look like compared to the Extreme." Anyboidy dobne comparisons.

Kholi I await your tests.



Lenny Levy
 
That's what it looks like. Same/Similar thing that I experienced with the Extreme. How much each stop differed I have no idea but it's the same on the Extreme and the same on the Ultimate. 1.4 to 2 there's a difference, one may say it's not enough and some might say it's the lifesaver in a pinch.

But it does behave in a similar fashion. When I get the Extreme in my hands sometime next week (hopefully) I'll be able to A/B them for Leny, but other than that it behaves just as you posted.

To say that there's no difference between 1.4 and 2 though isn't correct. There is, even if it can be deemed "negligible" to some. Horraaaay all done now, time to move on to something else.
 
That's great. My experience is that I can change the exposure about 1/6 stop even while my HVX reads out the same stop. Also the exposure change in the first fstop or so is not really a full stop. As I recall Barry Green and I talked about this once on these pages somewhere and couldn't figure out for sure why that was.

Lenny
 
We've tested the HV20, XH-A1, EX1 and HPX500 (17X fujinon lens). In every case we set them up baselined at about 50 IRE (using shutter speed to adjust) at f2.8. Closing down the shutter to f4.0 results in an adjustment to just under 70 IRE on each. In other words, with standard gamma, each camera shows just under 20 IRE in a 1 stop adjustment assuming you start from the middle of the inherent gamma curve of each camera. This behaviour is somewhat predicted by the 8 bit nature of the common formats in use. Keep in mind that we deliberately target the middle of the curve at 50 IRE as we know the usable latitude most are seeing is more like 8 or 9 stops but this gets stretched at the beginning and end of the curves. Lenny is correct in that none of these camera have the click fstop detents typical of an SLR camera lens, but there is comfort in repeatable results on cameras typically used by our customers.

Given that each camera has a different ISO rating, this is the only way we could find to test them somewhat objectively. It's also why we use this measurement to rate the adapter with a 50mm f1.4 lens attached at .5 to .7 stops total system loss relative to the video camera. On every camera it tests the same, so we're very confident in quoting these figures for our users as typical.
 
hi everyone, i am new at this forum and we want to buy adaptor for our xdcam F350 letus exrem or ultimate, i wonder which do you advice to us? and does letus adapter turn the image like M2? thank you
 
fotokaxa said:
hi everyone, i am new at this forum and we want to buy adaptor for our xdcam F350 letus exrem or ultimate, i wonder which do you advice to us? and does letus adapter turn the image like M2? thank you
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lurk around the forum a bit and see what you can pick up from other people's experience. Better yet, start a new thread :)
 
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