Film testing/reciprocity failure

[markbau]

My enlarging timer (Analyser Pro) only goes down to 1.15 seconds. Would the data from a film test (contact printing a step wedge onto a sheet of FP4) be useable? If not, any suggestions to shorten my exposure time?

 

[Nicholas Lindan]

1 second isn't enough time to encounter significant reciprocity failure.

If you can't shorten the time, lessen the light... If you are using your enlarger - er, stop it down, raise the head?

If you are using a different light source then an ND foil from Rosco (available from B&H).

Polarizers and, especially crossed polarizers, make good ND filters; make sure the crossed polarizers are linear or prepare yourself for some weirdness.

I found spending time contemplating crossed polarizers and the quantum behavior of photons leads to quite a bit of headscratching.

 

[markbau]

Light intensity isn't a problem. I started with a 2 stop ND and had to remove it and open up 5 stops after my first test was almost transparent.
My second test was better but still not enough exposure, the densest part of the neg is 1.53 above fb+fog. It goes to film base by step 17 on a Kodak step tablet.
I don't want to increase exposure time so lowering the enlarger head should get me closer to a good exposure.

 

[Bill Burk]

I was going to say don’t worry about it, but it’s one of the things you have to worry about.

Well since one second is where manufacturer says you don’t need reciprocity law failure adjustment, you should try to keep exposure to one second.

Can you use a flash instead of the enlarger light? That’s likely to give you 1/1000 exposure (the other end of region of good reciprocity).

Can you bring the head down lower?