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Vignette problem vintage lens on super35 sensor


Filip Aladdin
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Hi! I have a problem with a Cooke 25-250 T3.9. I tried it on the Panasonic Varicam 35 (shot with 4k and 2k still vignette) and I noticed a small vignette in the corners, even when I Zoomed to different focal length. Do you know what the problem could be? Something about the flange? or the sensor? Its a super35 mm sensor on the varicam.

Anyone knows why? I prefer not to crop it digitally after the shoot.

Thanks, Filip 

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It’s the rear element of the 35mm lens that wasn’t designed to cover large sensors. The real question is where your frame lines  are and is the vignette outside of those? The vignette will change as you zoom due to the zoom curve. 
 

G

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The Cooke 25-250 Cinetal zooms have an image circle of about 28mm, which is usually enough to just cover most standard S35 aspect ratios. As Greg said, where are your frame lines on that monitor image? Is your final image going to be all the way to the edges of that monitor?

The image circle is smallest at the wide end and should definitely not vignette at longer focal lengths, so check that the matte box for example is not shading the corners.

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The vignette will be dependent on both the aperture, the focal length and the focal distance.  Each zoom (even the same make and model) might have a slightly different "ramp" in the zoom and focus that could have an effect.  You will need to test with the lens at a range of stops and frame sizes and distances.  Often a wide open lens at a midpoint on the zoom will looks good with a mild maybe even pleasing fall-off and a deeper stop like maybe an 8 or 11 will make for a pretty hard vignette. 

Best of luck,

Neal Norton
DP

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