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testing film stock


J.M. O'Malley

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I need to do some stills tests for a short film. I'll be using 7222. There's no double-x on the market for still photography. Can I use plus-x, and push it to 200? Will the characteristic curve be the same? It is impossible to find out characteristic curves for film stock from Kodak. They use different chemicals for each film, so that the curves all come out looking the same.

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Can I use plus-x, and push it to 200? Will the characteristic curve be the same?

No. Pushing b/w stock will increase the gamma of the stock (more than it does for colour neg). Best bet would be to expose the stills stock and process it normally, if that is what you plan to do for the motion picture stock.

 

It is impossible to find out characteristic curves for film stock from Kodak.
Characteristic curves are really a combination of the emulsion and the development. As b/w processes vary from lab to lab (much more than the standardised ECN2 process for colour neg), there is no "typical" or "correct" curve independent of any particular lab.

 

Some labs (but by no means all) are able to expose sensitometric strips - if you supply a short length of your stock to the lab (and they are willing, for a price no doubt) they might be able to shoot a strip and process it for you to look at the curve.

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I figured it would at least change the grain structure. I study still photography also, and am learning about characteristic film curve. It seems that it is very difficult to know anything unless you are doing your own tests. I don't have a densitometer, so all my tests consist of "eyeballing it".

I should have mentioned before, I'm not using a lab because I'm afraid. I'll be processing the film using equipment I'm building. It's a short film so there wouldn't be any way for me to look at dailies and then correct for the lab's type of development.

Do you have advice from personal experience about PLUS-X versus DOUBLE-X? Are they similar in contrast, etc.?

Thanks for your help.

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