Well, I use SLIMTs for most of my Zone System contractions now, and simply develop at my "N" time. Also, for expansions I will often change the amount of the metaborate solution in PMK, or even add ascorbic acid. Time changes happen too. For me, it is a combination of changing developing time and other elements.
Ralph seems to have the ideal system for rollfilm Zone System. For those not willing or able to carry three camera bodies or backs around with them, I would refer them to my modified system on page one of this thread. It uses printing controls to deal with the different contrast ranges on one roll of film with some compensations for possible loss of shadow detail.
Just a comment about "push" processing while I'm here. Although the Zone System traditionally focuses on achieving detail in important shadows, the concepts and techniques involved apply equally well to available light photography and "pushing." "Pushing" describes a technique to get usable images from intentionally (or occasionally unintentionally) underexposed film for which the shadows are knowingly sacrificed. The situation that usually requires "pushing" is trying to photograph in inadequate light where camera and/or subject movement would cause blur at the "ideal" shutter speed. The aperture/shutter speed combination needed to avoid blur won't give enough light to expose the film "properly," i.e., deliver shadow detail. When confronted with this scenario, one simply makes the photos at the aperture/shutter combination needed to avoid blur and attempts to compensate for the resulting underexposure by increasing development time, changing developer, or a combination of the two.
"Pushing" consists, then, of two elements. underexposure and overdevelopment. It is the underexposure element that takes "pushing" outside the traditional Zone System structure. True, the shadow detail gets lost when "pushing," but the overdevelopment raises the underexposed highlights to the desired level, allowing one to make a full-range print. Indeed, done right, it does ensure that the negative has a contrast range that matches that of normal-grade paper. One could think of it in Zone System terms, e.g., "the shutter speed I need to avoid blur makes the highlights fall on Zone VI. I need to expand that to Zone VIII, so I'll indicate N+2 development. Anything below values that fall on Zone III (which are mid-tones in this scenario) will print as black without detail, but I understand this, can live with it, and might even like it. At least I'll get an image that is not blurry, even if the entire scale of the print consists of blank shadows, dark "mid-tones" and contrasty highlights stretched out from black to white in the print. Although "pushers" think in terms of increased E.I. and "push processing" (which is nothing more than extended development), the results are nevertheless the same.
Zone System users use expansions to get more contrast out of low-contrast scenes. Shadow detail is maintained. "Pushers" settle for more contrast from already high-contrast scenes in order to optimize shutter speed and aperture by letting shadows go black and "pushing" the highlights up to a negative density that prints as a highlight while letting the low density areas of the negative still print black. Much the same effect can be had to some extent by using a higher paper grade, but in extreme situations, "pushing" the film is the better solution for many. Still others like the look of underexposed and overdeveloped film and "push" in situations where it might not otherwise be necessary for aesthetic reasons.
I happen not to like the look of "pushing" and do not use it except when I think the image itself is worth what I consider the "technical inadequacy" of being able to capture it on film. That said, many good and even famous documentary, news, and other low-light photographs would not have been able to be made otherwise. Pushing, therefore is a valuable, but different tool than traditional Zone System expansion. It is still applied senitometry, which, after all, is what the Zone System, BTZS, and many other systems are as well.
Down from the soapbox now...
Best,
Doremus Scudder
www.DoremusScudder.com