A good book on LF exposure, reciprocity and bellows extension exposure compensation

[r.e.]

I am looking for a resource ... that covers, in detail, the issues of film reciprocity...

I'll just comment on the nuts and bolts of the computation. The available information depends on what film you're talking about.

Kodak's data sheet for Portra 160 and Portra 400 tells you nothing about how to compute reciprocity failure. It tells you to "experiment". Many people use an app called Reciprocity Timer, about which there are discussions on this and other photography forums.

Ilford, on the other hand, does give guidance on computing reciprocity failure for its films: Ilford Film Reciprocity Failure Compensation. For Ilford, you can use Reciprocity Timer or do the math. The math is dead simple, and I imagine that every smartphone calculator has the necessary x^y function. I've just finished making an exposure worksheet. Ilford's formula, for HP4+ and HP5+, is in the last box of the worksheet, which is attached to post #8 in this current thread: https://www.largeformatphotography.i...sure-Worksheet

If you read Ilford's data sheet on reciprocity failure, note the caveats to the calculations.

[WarrenXL]

I'll just comment on the nuts and bolts of the computation. The available information depends on what film you're talking about.

Kodak's data sheet for Portra 160 and Portra 400 tells you nothing about how to compute reciprocity failure. It tells you to "experiment". Many people use an app called Reciprocity Timer, about which there are discussions on this and other photography forums.

Ilford, on the other hand, does give guidance on computing reciprocity failure for its films: Ilford Film Reciprocity Failure Compensation. For Ilford, you can use Reciprocity Timer or do the math. The math is dead simple, and I imagine that every smartphone calculator has the necessary x^y function. I've just finished making an exposure worksheet. Ilford's formula, for HP4+ and HP5+, is in the last box of the worksheet, which is attached to post #8 in this current thread: https://www.largeformatphotography.i...sure-Worksheet

If you read Ilford's data sheet on reciprocity failure, note the caveats to the calculations.

Instead of a Kodak specification that doesn't give specific data, it's easier to use apps that give specific recommendations.

[Alan Klein]

Instead of a Kodak specification that doesn't give specific data, it's easier to use apps that give specific recommendations.

Which apps are recommended that are accurate and well researched?