Fp4 film

[Dean Wilmot]

Hi all, I am changing from a jobo cpe3 to a cpp3 processor, does anyone know if FP4 120 film is identical to 4x5 sheet film for zone system test results? I’m wondering if I’ll need to retest for both formats? Also are the rotation speeds for both processors the same? Thanks

[Andrew O'Neill]

Same.

[neil poulsen]

I tried this with HP5 and conducted my tests on 120 film. I didn't care for the resulting developments that 120 gave me for 4x5, so I redid the tests on 4x5 film and got better results.

[Jim Noel]

I have not found them to have the same characteristic curve

[Jerry Bodine]

Dean - I queried Ilford a few years back about this very question regarding a difference in test results for a specific film in 120 vs sheet. Here's an excerpt from their reply:

"... there can be small differences between 35mm, 120 and sheet film as these do use different bases and slightly different emulsions. Although we endeavor to manufacture all three types to be as close as possible in order for development times to be consistent across the range for any one film type (and they are for most practical purposes) someone carrying out the exacting type of testing you describe will inevitably pick up small differences."

[neil poulsen]

This was years ago. Prior to using my 120 results for 4x5, I called Ilford Tech Support. They indicated that 120 and 4x5 HP5 should be sensitometrically the same. But as I say, that was not my experience.

[Dean Wilmot]

Thanks very much all.