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Hi Dennis,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.
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.
I JUST TAKE TO LONG TO WRITE
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 rangeJust pm your address/phone number and email, and it'll be there in 2 days.
Cheers![]()
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.
I JUST TAKE TO LONG TO WRITE
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)...
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.[/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.
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!