Reciprocity Failure with B&W Chromogenic films

[Eric Rose]

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

 

[SMBooth]

They did make XP2 in 4x5 and 5x4.

 

[BMbikerider]

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

The difference will be because they were produced by different companies with differing formulae (I much prefered CN400 though)

 

[Rudeofus]

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.

I am not sure where you got this '100 minutes' number from. The data sheet provided by Kodak here (grab it while it's still there) states:

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.

It would have been extremely surprising to see BW400CN fare so much better than their latest Portra series film stock.

 

[Lachlan Young]

Howard Bond's article on reciprocity from 2003 argues that the curve Ilford provides is both generic & out of date - I suspect Ilford has felt there has been little need/ interest in bringing it up to date.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

 

[RalphLambrecht]

Howard Bond's article on reciprocity from 2003 argues that the curve Ilford provides is both generic & out of date - I suspect Ilford has felt there has been little need/ interest in bringing it up to date.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

Award Bond is a pretty reliable resource.

 

[Eric Rose]

Yes I knew they made xp2 in 4x5 at one point, just wish they would still do it.

I would be happy to produce new and accurate reciprocity tables for Ilford if they paid me to do it.