# What is the gamma value of Kodak 5201 & 5212

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### #1 Evangelos Achillopoulos

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Posted 08 August 2007 - 05:33 PM

Hello to forum gurus, another question for you guys.

I know from the available bibliography that intermediate stock like 2242/5242 has a gamma of 0,6 and again this is more of a feeling than a certainty, no ware in Kodak specification is stated what?s the gamma value of a film stock.

So the question is:

What is the gamma value of Kodak 5201 and Kodak 5212?

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### #2 Dirk DeJonghe

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Posted 09 August 2007 - 05:34 AM

5242/7242 has a gamma of 1.0 by defintion since it is made to print as interpositive from original negative and as duplicate negative from interpositive. Since the duplicate negative has to be intercutable with the original, the gamma cannot be anything else but 1.0.

Consider the gamma of OCN to be about 0.55, B&W original camera negative is around 0.65.
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### #3 Brian Pritchard

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Posted 09 August 2007 - 05:46 AM

You can calculate the gamma of the various Kodak film stocks from the graphs on their website of characteristic curves. For example http://www.kodak.com...mp;lc=en#graphs gives you the curves for 5201. The left hand scale is density and the lower scale is Log Exposure. The density change over 1.0 Log E gives you the gamma. In the case of the red layer for 5201 the density change from Log E -1.00 to 0.00 is 0.5 to 1.10 approximately, giving a gamma of 1.10 - 0.5 = 0.6. These are general curves and do not apply to particular emulsions. Stock manufacturers use different ways to calculate the contrast of a film according to its purpose. Gamma is not usually used as it is just the slope of the straight line portion of the curve. It does give you an approximation of the contrast. Most film stocks fall into regular categories, camera stocks are around 0.6, intermediate films around 1.0, B/W Duplicating positive 1.6 and so on. If you push or pull process stocks you will change the gamma (contrast).
Brian
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### #4 John Pytlak RIP

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Posted 09 August 2007 - 07:53 AM

You can calculate the gamma of the various Kodak film stocks from the graphs on their website of characteristic curves. For example http://www.kodak.com...mp;lc=en#graphs gives you the curves for 5201. The left hand scale is density and the lower scale is Log Exposure. The density change over 1.0 Log E gives you the gamma. In the case of the red layer for 5201 the density change from Log E -1.00 to 0.00 is 0.5 to 1.10 approximately, giving a gamma of 1.10 - 0.5 = 0.6. These are general curves and do not apply to particular emulsions. Stock manufacturers use different ways to calculate the contrast of a film according to its purpose. Gamma is not usually used as it is just the slope of the straight line portion of the curve. It does give you an approximation of the contrast. Most film stocks fall into regular categories, camera stocks are around 0.6, intermediate films around 1.0, B/W Duplicating positive 1.6 and so on. If you push or pull process stocks you will change the gamma (contrast).
Brian

Remember, the particular lab process you are using will have some effect on the sensitometry of the process and what "gamma" and curve shape you will get. For detailed results, work closely with your lab, and better yet, actually run some picture and exposure tests.
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### #5 Evangelos Achillopoulos

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Posted 16 August 2007 - 07:41 AM

Sorry guys for not reply promptly but somehow I was dropped by the system and didn?t allow me to post? Now it?s OK

Big thanks to John, and I feel too small to say something about you? Just my best wishes and god be with you.

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### #6 Chris Keth

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Posted 16 August 2007 - 04:58 PM

Remember, the particular lab process you are using will have some effect on the sensitometry of the process and what "gamma" and curve shape you will get. For detailed results, work closely with your lab, and better yet, actually run some picture and exposure tests.

You film guys have it good. No other manufacturing business can tell you to run your own tests regarding their products.
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