Reciprocity Failure with B&W Chromogenic films

Eric Rose said:

I was looking at the data sheets for both Kodak CN400 and Ilford XP2 with respect to reciprocity exposure adjustments. On the sheet I have for CN400 it states there is no adjustment needed even up to 100 minutes. While the Ilford tech sheet ( http://www.ilfordphoto.com/Webfiles/201142711321939.pdf ) shows a curve similar to other traditional B&W films.

Since they are both suppose to be chromogenic why the difference?

On another not I sure wish they produced XP2 in 4x5.

Eric

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Eric Rose said:

I was looking at the data sheets for both Kodak CN400 and Ilford XP2 with respect to reciprocity exposure adjustments. On the sheet I have for CN400 it states there is no adjustment needed even up to 100 minutes. While the Ilford tech sheet ( http://www.ilfordphoto.com/Webfiles/201142711321939.pdf ) shows a curve similar to other traditional B&W films.

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No exposure compensation for reciprocity failure is
necessary for exposures between 1/10,000 and 120 seconds.
We do not recommend exposures longer than 120 seconds.

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Lachlan Young said:

Howard Bond's article on reciprocity from 2003 argues that the curve Ilford provides is both generic & out of date - I suspect Ilford has felt there has been little need/ interest in bringing it up to date. Test & compare would probably be the first step...

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