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Do video lenses behave differently from Film Lenses?


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#1 Bob Hayes

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Posted 20 March 2008 - 05:53 PM

I have a strange question. Some one told me that if I put a video lens on a film camera the colors will not all focus on the film plane because they are staggered to fall onto different chips. I thought the prism did all the separating and I also thought a lens was a lens. Granted some lenses have better quality and some are designed to hit a smaller target. I had never heard that video lenses behaved this way until recently.
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#2 Michael Nash

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Posted 20 March 2008 - 06:13 PM

It's true. The prism does do the separating, but focuses each color at slightly different distances. 2/3" video lenses are calibrated for these distances, not a single focal plane.

There's an adapter that corrects for this, which is what allows single-sensor cameras like the RED to use 2/3" video lenses.

http://pro35.com/zgc...5256EC9005F5789
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#3 Mitch Gross

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Posted 20 March 2008 - 08:39 PM

It's true. The prism does do the separating, but focuses each color at slightly different distances. 2/3" video lenses are calibrated for these distances, not a single focal plane.

There's an adapter that corrects for this, which is what allows single-sensor cameras like the RED to use 2/3" video lenses.

http://pro35.com/zgc...5256EC9005F5789

Yes that's the Abekas device. They make one for Super-16 that corrects back for the color wavelengths and another for 35mm that does the same but also incorporates a doubler (2x magnifier) to cover the image area (and eat two stops of light).

Abel has the S-16 unit in rental, which can also be used on a RED shooting in 2K mode.
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#4 Evangelos Achillopoulos

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Posted 21 March 2008 - 05:03 PM

Where can I find more info about that ?difference? that 2/3 prism lens has?

How much different they are or what is the result in use of flat photo lenses in prism based cameras?

Do they introduce aberrations and what kind?
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#5 Michael Nash

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Posted 21 March 2008 - 05:30 PM

Where can I find more info about that ?difference? that 2/3 prism lens has?

How much different they are or what is the result in use of flat photo lenses in prism based cameras?

Do they introduce aberrations and what kind?


On a technical level, I don't know; wish I could help you.

But on a practical level, you can't combine the different lens/camera formats without an adapter anyway, so you might as well use the right one...

http://www.smsprod.c...angenieux4.html
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#6 Mitch Gross

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Posted 24 March 2008 - 10:25 AM

Search the archives of this forum (cinematography.com), as well as cinematography.net and wikipedia.
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