Zone System for Roll Film
I shoot sheet film, and use (my version of) the Zone System. I spot meter and develop each sheet separately using a number of different development schemes.
That said, if I were shooting roll film, especially 35mm and/or handheld and spontaneous styles, I would ditch all the development variations and just choose one, standard, time for all my negs. I would also probably use my in-camera meter and base exposures on an E.I. determined by testing with that meter.
I've been giving this subject a lot of thought lately and have arrived at the following method for metering and developing roll film in a modified exposure/development system that retains the heart of the Zone System but allows much more rapid shooting. In this system there is only one, "Normal," development time; different contrast negatives are dealt with by changing paper grades/contrast.
First, with small film, you should standardize your negative contrast to print well on a slightly higher contrast grade paper, I'd use grade 3. This allows the negatives to be developed to a smaller density range and decreases grain.
Next, decided how you want to meter, either "placing the shadows" or using the "averaging method" along with an in-camera meter ("intelligent" in-camera meters are remarkably good for most subjects). If you, like me, would use an in-camera averaging method, skip the next paragraph.
Exposure Method for Shadow Metering
If you choose to "place the shadows," then meter an important shadow and place it on the appropriate Zone, e.g., Zone III for blacks with detail or Zone IV for "luminous" fully detailed shadows. Do your E.I. and development tests to arrive at "Normal" development and then use that development time for everything. With this metering technique, you should overexpose scenes with low contrast by one stop, i.e., place the shadows higher by a Zone, making sure that the high values do not go past Zone VIII. You can meter the highlights to be sure, but with experience you can accurately identify a low-contrast situation and know when to overexpose without taking the time to meter the highlights to see where they fall. This overexposure gets the shadow values up higher on the film's characteristic curve and gives more separation than less exposure. For very contrasty scenes, just place the shadows as normal and shoot away. The negs will be contrasty, but most films retain adequate separation up to Zone XII and beyond. Just print with a lower contrast grade paper.
Exposure Method for Average Metering
If you decide to use the "averaging" metering method (e.g., in-camera meter), you should determine E.I. and "Normal" development time with that method. With this metering technique, you need to recognize contrasty situations (as opposed to recognizing the low-contrast situations using the "place the shadows method") and then
overexpose one stop for high-contrast situations and two stops for extremely high-contrast, very bright situations (this seems counter-intuitive at first, but is quite logical and correct in this system). You overexpose high-contrast scenes because your meter will tend to expose for a middle value that results in dropping the shadow values. Overexposing compensates for this. You end up with a contrasty negative that you would then print on low-contrast paper. Note that the averaging meter will automatically place shadows higher than normal in a low-contrast situation. This is exactly what you want to get the most separation in the low values.
You can use both methods alternately if you test them both and note the difference in effective E.I. (there may be none, but usually there is a little difference). Just set your E.I. for the method you decide to use at the time: "place the shadows" when you have time and are working carefully, "averaging" when you need speed, or need to rely on the camera's auto-exposure features.
Of course, you may also want to shoot entire rolls in low light and use classic "push-processing" (which is simply underexposing and overdeveloping with the expected loss of shadow detail and increase in contrast) for that "look" as well. In this case, you would rate your film higher and increase development. This would have to be tested as well. However, for the occasional low-light shot mixed in with other exposures on one roll, just use the averaging technique above and print on higher-contrast paper.
This might seem long, but once you have all the above tested and in-hand, so to speak, you have just about all the tools you need to expose and develop printable negatives and still be able to fully utilize the advantages of smaller cameras and roll film. And, you can shoot just about any contrast situation on the same roll and, in all but the most extreme situations, be assured of negatives that will print.
The heart of this method (as with the Zone System) is determining your E.I. and developing time. I recommend using a "proper proof" in which blank, developed film is contact printed so that it is a shade of black almost as black as the maximum paper black. You can do a test strip to determine the "proper-proofing time" and then note it, enlarger head height, lens aperture, etc. for future proofing. Then, using the "proper-proofing time to evaluate your test negatives, adjust exposure so your shadows look as you wish them to and adjust your developing time so that the highlights in a "Normal" scene have the detail you want. It boils down to knowing what to expect.
Once you have your standards set, you can use the "proper proof" as a tool to help you know what grade paper to use. Contrasty scenes will have adequate shadow detail, but the highlights will be overexposed. This means print on a lower-contrast grade paper. Low contrast scenes should have lighter shadows than "normal" and possibly muddy highlights as well. This means print on a higher-contrast grade paper.
Best and good luck,
Doremus Scudder
www.DoremusScudder.com