Some thoughts:

I shoot sheet film and practice the Zone System. I test for many different development schemes (N, N+s and N-s). However, for roll film, when you will be shooting subjects of different contrast on the same roll, it is most important to simply find an N that gives you good shadow detail and manageable highlights. Since you use a spot meter, all you would then have to do is place an important shadow. I would deal with the different contrast situations by changing paper grade. And I would tailor my N to grade 2.5 or 3 to give a bit more latitude for high-contrast subjects.

Your test could (and I think should) be done without a densitometer, but rather by making proper proofs of your negatives on the paper and grade you will mostly use. This takes your enlarging system into account as well.

Furthermore, I think you should set up your targets in a situation where you would have "normal" flare. I set up a target card in a scene and like to have it take up no more than about a third of the entire scene. I use darker cards for the shadow values. That way I take an "average" amount of flare into account when making the test. Otherwise, you can test out everything and then get significantly higher shadow values in practice due to flare.

I find keying Zone VIII as just below paper-base white to be my most important highlight benchmark, not Zone VII.

I also like having the prints of my tests to remind me of just what I'm going to get when I place a certain value in a Zone. Densitometer readings don't help me to visualize. I used to make Zone Rulers (prints of Zone 0 through the highest Zone for a particular development scheme) to help me learn to visualize tones. I no longer need them, but they were indispensable at the beginning. One also finds that Zones for a particular scheme don't always follow the classic ZS descriptions. When Zone III and Zone VIII are perfect, Zone V is often far from 18% grey. It's more important to know what you'll get when you expose than to try to match some arbitrary standard.

The amount of variables in a photographic system is huge and little errors add up fast. Getting to within one Zone of my desired placement/development is way close enough for me. Printing controls are more than adequate for that. Realize that even your tests can be significantly "off," and make future adjustments based on field notes and experience.

Best,

Doremus


www.DoremusScudder.com