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pro 35 white shading


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#1 mosh mishali

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Posted 06 January 2008 - 11:26 AM

hey

I will be an AC in a feature film next month, we will use the SONY F900R with a pro35 adaptor and a set of prime lenses.
the rental place have adjusted the white shading for the pro 35 adaptor but they didn't make lens file for each lens, is that enough or should i make lens fils for each different lens? also if there is a problem whats the best way to adjust it on the set? (if its possibole - must i have a vectorscop?)

thank a head

mosh
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#2 Mitch Gross

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Posted 07 January 2008 - 11:09 AM

If you have a regular matched set of primes then you will only need the one white shading setting. Adjusting this in the field is not a great idea. You need a waveform, a perfectly flat white image (we use an Integration Sphere that is like a huge ping pong ball with a hole cut in it to stick the lens) and some skill. If you have never done it before I'd really recommend staying away.
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#3 A. Whitehouse

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Posted 08 January 2008 - 07:35 AM

If you have a regular matched set of primes then you will only need the one white shading setting. Adjusting this in the field is not a great idea. You need a waveform, a perfectly flat white image (we use an Integration Sphere that is like a huge ping pong ball with a hole cut in it to stick the lens) and some skill. If you have never done it before I'd really recommend staying away.


Ive seen some pretty dramatic shifts and vignetting using the pro 35. Severe green vignetting and dark corners. I don't know anything about the white shading settings, could you explain them further?

Is this something which will happen over time and needs adjusting regularly during a production or is it something I could test for at check out and feel secure that it would stay in place for the rest of the shoot? Is it in the spinning mirror optics or something else? I don't know much about the mechanism of the pro 35 and my experience with them has been limited to short productions, week long rentals at the most. I also never have a decent monitor on set which would only expose a problem further which I don't know how to fix.

Could this misalignment effect sharpness and focus as well?

Sasha
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#4 Mitch Gross

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Posted 08 January 2008 - 10:28 AM

It is a prismatic effect which creates green on the top of the frame shifting to magenta on the bottom. A proper white shading eliminates the problem and once set will remain stable for as long as you need it.

A white shading is imperative when using a Pro35 on any camera. If your rental house does not do this for you before checkout, then switch rental houses! This is not something to do in the field.
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#5 A. Whitehouse

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Posted 08 January 2008 - 05:40 PM

It is a prismatic effect which creates green on the top of the frame shifting to magenta on the bottom. A proper white shading eliminates the problem and once set will remain stable for as long as you need it.

A white shading is imperative when using a Pro35 on any camera. If your rental house does not do this for you before checkout, then switch rental houses! This is not something to do in the field.


Thanks Mitch,
Yeah a Green to Magenta shift is exactly what I've seen. From packages rented from a few different rental houses. Thanks for the heads up.
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