Sensor Illumination with Small Exit Pupil/Rear Element?

[Jorge Díaz-Amador]

Has anyone had the chance to test older retrofocus lens designs with small rear elements and small diameter exit pupils on the RED One? Some examples of these lenses would be:

Zeiss Distagon 16mm T2.1
Zeiss Distagon 24mm T2.1
Zeiss Planar 32mm T2.1

Cooke Speed Panchro 18mm, 25mm, 32mm, 40mm

I am curious to know if these lens designs will illuminate the RED sensor with acceptable light fall off in the corners. All lenses have fall off, but newer designs and faster lenses with larger rear elements and exit pupils tend to reduce this to a minimum.

As many of you have heard (or have personal experince) the lenses mentioned above will have unacceptable light fall off on a diffusing screen optical adapter (such as P+S Mini-35, P+S Pro-35, MovieTUBE, etc). But these products use diffusing screens (ground glass) which respond differently to a solid state sensor.

Obviously, still camera lenses designed for the Leica frame 24 x 36mm will almost never have visible fall-off on a Super 35 sized sensor. But there are other major issues with still camera lens designs that make them less desirable for professional production work on a high resolution digital cine camera.

Jorge Diaz-Amador
CinemaTechnic, Inc.
Miami, FL USA

[Stephen Williams]

Hi Jorge,

I tested the Zeiss 16 & 24 on a Phantom HD. The 16 portholed until stopped down until T4 the 24 2.8/4 split. The 32 was missing from the set, the longer lenses were fine,

Stephen

[Jorge Díaz-Amador]

Stephen,

Thanks for the info. It seems like the problem is not as bad on a solid state sensor as on a ground glass. I don't think those lenses are usable at all on the P+S unit. How big is the sensor on the Phantom?

The 32mm Planar is a very small lens optically. A compact symmetrical Double-Gauss design. The front element on that one is behind the flange of the PL Mount! It will probably exhibit similar results to the 24mm. Once you get to the 50mm, they are all Planars, and the exit pupils get much bigger.

-JDA

[Stephen Williams]

Hi Jorge,

The sensor is 2048 x 2048, the figures quoted for shooting 1.85:1 using an active pixel area of 25.6mm x 13.85mm (2048 X 1108 pixels) so I guess the active sensor is 25.6 x 25.6.

I tested the lenses against a white background, I was looking for that problem.

Stephen

[Greg M]

My Red should arrive in a few weeks and this is the first thing we are testing. I have a set of Ultra Primes and a set of Standard Speeds. I'll post the results as soon as we get our camera.

Someone else reported earlier that he used a set of Standard Speeds and he did not see any fall off. I believe it was Evin.

[Stephen Williams]

Hi,

Some Standard speeds were used on "crossing the line" the issue is wide open and against a flat colored background. FWIW The Zoom supplied with my D70 also portholes.

Stephen

[Jorge Díaz-Amador]

Hi Jorge,

The sensor is 2048 x 2048, the figures quoted for shooting 1.85:1 using an active pixel area of 25.6mm x 13.85mm (2048 X 1108 pixels) so I guess the active sensor is 25.6 x 25.6.

I tested the lenses against a white background, I was looking for that problem.

Stephen

That is a BIG sensor! ANSI Super 35mm spec is 24.9mm wide, and DIN is 24.05. And that's full camera aperture. Scanned/projected is smaller. I understand the RED sensor is 24.5mm wide, about halfway between DIN and ANSI.

-JDA

[Mick van Rossum, NSC]

Stephen,

Thanks for the info. It seems like the problem is not as bad on a solid state sensor as on a ground glass. I don't think those lenses are usable at all on the P+S unit. How big is the sensor on the Phantom?

The 32mm Planar is a very small lens optically. A compact symmetrical Double-Gauss design. The front element on that one is behind the flange of the PL Mount! It will probably exhibit similar results to the 24mm. Once you get to the 50mm, they are all Planars, and the exit pupils get much bigger.

-JDA

I might be able to test next week, however I took my 32/T2.1 to the RED booth at IBC, looking for this problem, but saw no portholing.

In my experience the 32 and the 28 are the worst concerning portholing (you can even see it on Super 35 negative. though very slightly). So that is good news. However not tested very intensively so far on RED.

Cheers

Mick van Rossum NSC

[Stephen Williams]

I might be able to test next week, however I took my 32/T2.1 to the RED booth at IBC, looking for this problem, but saw no portholing.

In my experience the 32 and the 28 are the worst concerning portholing (you can even see it on Super 35 negative. though very slightly). So that is good news. However not tested very intensively so far on RED.

Cheers

Mick van Rossum NSC

Hi Mick,

I doubt you got much of a chance to see with all the chaos of IBC, unless you had a wave form monitor plus an evenly lit white surface. Lets face it, the monitoring at IBC was hardly state of the art!

Stephen

[Mick van Rossum, NSC]

So I put my set of lenses on a RED seeing how they did, especially the wider angles, and Stephen, yes they do vignet, especially when I put them on a white test bench. Especially when you see it on a scope it is kind of scary. It doesn't make them unusable but for let's say a white limbo set with an open aperture, one really needs a serious window in CC to get it fixed. In general I don't see much of a problem working with them, they work very nice with the Mysterium sensor and the fall off to the sides is -for me- acceptable. The 32 was the worst, the 16 and 24 were a bit better. But again something easy to fix in post.
More test results later

Cheers

Mick van Rossum NSC

[Petros Nousias]

How much did you have to stop down the 32 in order for the portholing to disappear?

[Mick van Rossum, NSC]

How much did you have to stop down the 32 in order for the portholing to disappear?

4 to get rid of the most

[Petros Nousias]

how about the rest up to 32? also at T4?
did you also check the 20 and 28mm?

[Mick van Rossum, NSC]

how about the rest up to 32? also at T4?
did you also check the 20 and 28mm?

Did not test those that well, I don't have the 20 and 28, I know the 28 is as bad as the 32 (same design) my guess is that the 20 is like the 24 and 16. I can only compare it to 35 stuff I shot with those lenses.