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Tri-X Reversal ASA


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#1 Renny McCauley

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Posted 01 November 2008 - 02:09 PM

This is probably a stupid question, but I was looking at the ASA ratings for Tri-X 16mm reversal film. Kodak seems to list a tungsten rating (160) and a daylight rating (200). Why are there two different ratings? It looks like all the b&w stocks are like that, but not the color stocks. Thanks for the help.

Renny
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#2 Adrian Sierkowski

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Posted 01 November 2008 - 03:22 PM

It has to do with the sensitivity of parts of the emulsion to differing parts of the visual light spectrum; notably blue and red. It's more sensitive to blue; hence the faster speed in daylight, than it is to red. This is true of B/w film only. Color film is balanced for certain color temperatures and it's EI based on that.
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#3 Charles MacDonald

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Posted 01 November 2008 - 05:40 PM

Color film is balanced for certain color temperatures and it's EI based on that.

If you want to shoot colour film at other temperatures, ie daylight film undertungsten, the label doestwll you what EI ot start with with the corection filter. Thew filters are not needed for B&W hence the instuctions focus on the light itelf.
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#4 Renny McCauley

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Posted 01 November 2008 - 07:53 PM

It has to do with the sensitivity of parts of the emulsion to differing parts of the visual light spectrum; notably blue and red. It's more sensitive to blue; hence the faster speed in daylight, than it is to red. This is true of B/w film only. Color film is balanced for certain color temperatures and it's EI based on that.

Okay, that makes perfect sense. I figured this was a simple question. Thanks,
Renny
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