Cooke 20-100-or 18-100 owners step in please.

N

NAHA41

Member
F3 lense vignette copy.jpg
I recently purchased a cooke 20-100 zoom lens that is vignetting only on the right side of the frame at 20 mm - 21 mm.
The lense is collomated and tracks within 1/4 of an inch, and comes from a very respected lens technician.

There is a concern that the sensor is not aligned correctly. (my F3 is brand new)

Any other cooke zoom owners have this issue ?

There is no matte box, just the lense.

Love the lens, and am trying to figure this out.

Thanks
 
If it's any consolation, ritual 18-100/T3.1 user here and have never seen that. But, I'm on MX. Even still, shooting 4.5K (Widest you can shoot MX) it has never shown up on the 18 end.
 
This may seem too simple:

I'd check the PL adapter to make sure those little pins are lined up. They have to be pushed in before you tighten the collar. Otherwise I've noticed the adapter doesn't sit flat.

Then I'd make sure the lens flange hasn't been bent.
 
I shoot a 20-100 on my Red One MX at 4.5K wide screen all the time and I never see this problem. You should not see this on the F3. I too suspect misallignment.
 
Have you tried removing the front matte from the 20-100 to see is this takes care of the problem? I remove mine to fully cover a S35 size sensor at full wide.
 
The sensor area on the F3 is larger than the RED One. It is closer to Super-35 while the RED One is closer to Academy 35. The old 20-100 was designed to cover Academy 35, not Super-35.

The lens does not cover the F3. I have seen this before.
 
I've always found it annoying that most charts seem to have different dimensions listed and the manufacturers often don't give anything but the general category size.

Able Cine has something I like, a percentage summary. The Red One is 89%, so comments from guys about their Red don't count on this issue.

The F3 is 95% and Alexa is 96% the size of S35 film. Epic-x is 104%, which means a lot of cinema lenses won't work on it.

Here's a good comparison of film S35 to pretty much all the digital sizes in the same ball park. You need to see the full sized image:

http://blog.abelcine.com/wp-content/uploads/2010/08/35mmdigitalsensors_2011.jpg

Then here are the others.

Duclos Lenses
http://www.ducloslenses.com/ref/formatref.pdf

Sony
Super-35mm-image-size.jpg

Hot Rod Cameras
http://www.hotrodcameras.com/wp-content/uploads/2009/06/sensor-size-chart-web2.jpg

Red camera
http://red.cachefly.net/14/mysterium.jpg

http://www.logrithmic.com/wp-content/uploads/2010/12/RED_sensor_chart.jpg

http://dslrfilm.com/wp-content/uploads/2009/09/sensorsizes_06_cheatsheet.png

http://images.anandtech.com/reviews/cameras/2008/sensor-formats/sensor-size.jpg

http://tom11.com/images/blog/sensor-sizes-1.gif
 
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Thanks for all the reply's guys. Really appreciate it. We are going to try the lens on another F3 later this week. I am very sure that what we are seeing is the front matte / element protector on the cooke 20-100.
Hate to lose 2 mm
 
In my younger days we used these cookes with Academy aperture which was only 22.047mm wide and used for 1.33 and 1.85 formats. When we started to use full aperture 24.89 mm ( Super 35) we had to remove the front mask to keep from vignetting and even then there would be a small amount of vignetting in the corners of the 1.85 format when at the widest angle . Your right side of the frame has a very soft cutoff and it has a very slight curve to it suggesting something in front of the lens is vignetting. The mask much like a matte box was used to cut down on internal relections from stray light. A new mask could be made for the 16/9 format that would move the edges out probably enough to give you a clean image. Most likely the optical centers of the lens and the F3 sensors are not the same. In motion picture projection, the film aperture is about 4% smaller the the negative image , so the problem would not be seen. On a TV screen it won't be seen either. On motion picture film images there was all kinds of crap on the edges that you just didn't see in projection.
 
Get an 18-100. Its a better lens anyhow. No breathing, tad sharper and newer, hence usually in better mechanical shape. They can be had for under 10grand. I LOVE mine. Prettiest lens I have.
 
Duke M. said:
I've always found it annoying that most charts seem to have different dimensions listed and the manufacturers often don't give anything but the general category size.

Able Cine has something I like, a percentage summary. The Red One is 89%, so comments from guys about their Red don't count on this issue.

The F3 is 95% and Alexa is 96% the size of S35 film. Epic-x is 104%, which means a lot of cinema lenses won't work on it.

Here's a good comparison of film S35 to pretty much all the digital sizes in the same ball park. You need to see the full sized image:

http://blog.abelcine.com/wp-content/uploads/2010/08/35mmdigitalsensors_2011.jpg
Click to expand...

Thanks Duke, as author of that chart I can tell you that it was a huge task to try to make it as clear and helpful to people as possible. Still doesn't please everyone, but I'd like to think it's better than not having something.
 
I must say that's one of the best charts I've seen. It has a visual reference, numeric specs and a summary (the percentages.) If you can't figure it out with that chart you'd need to buy a clue.
 
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