Had a few conversations with people still shooting film based on that crappy interview that I did. Quite a few of them had some questions about whether I use the Zone system for exposure and development as well as some questions about the Zone system. I thought I would share the crux of a couple of things that were revelations to them as well as myself about 20-25 years ago. Even if you don't shoot film there are a couple of things that you might find helpful in your digital endeavors.
I am not going to rehash the zone system here - Ansel did a fine job of that in his three classic books a long time ago - sort of. Let's just say it is a proposed system of gaining control over the medium so that the tones you envision are reproduced on your final print. The key word here is "envision". One problem is that in countless examples explaining the zone system somebody else like Ansel explains the tones that they envision and some how those verbal descriptions seep into your subconscious as rules of what tone something is supposed to be. The second problem is that Zone VIII, IX, and X are treated in a lot of zone system tutorials as second class zone citizens, somehow to be avoided - sort of like "blown highlights" in digital.
In reality almost any photograph of any subject that lacks those last three zones will look flat and lifeless and way too dark. I am going to go off the deep end here and I am sure there will people that will disagree but Zone VII highlights are not the most important - Zone VIII bordering on Zone IX are the most important highlights in a photograph. Zone VIII is also the most important zone in the whole of the zone system. Not only is this the zone that makes things glow and sparkle especially in it's upper regions but it is also the zone that is the target zone for all contrast manipulation during development when zone people talk about N, N+, and N- contrast expansions and contractions.
Now here is the real important tidbit that will shatter all zone system laws, religious texts, beliefs forever more. Are you ready? There is no turning back once you open this Pandora's box - caucasian skin in sun, or any light for that matter IS NOT ZONE VI. Nope that's right, I really do not know how many times that the brilliant zone system powers that be, including AA, has used the absolutely terrible example of caucasian skin in sunlight as the archetypical example of zone a VI tone but this is not just a matter of taste - it is dead wrong. If you expose develop and print caucasian skin at zone VI your print will look like absolute shit.
Maybe this is why 99% of zone system photographers are landscape guys/gals. Given my overly creative imagination I can envision a person learning to do the zone system the right way a long time ago making wonderfully detailed landscapes and then taking a picture of an actual person, dutifully and carefully exposing developing and printing for zone VI skin and being so depressed with how horrible the image is that he/she swears off taking pictures of people forever more. Probably not but I am just making a point.
Caucasian looks the best and so do your prints when skin tones are mostly Zone VII going into and having a healthy dose of Zone VIII. If there are specular highlights they may go into zone IX or even - oh my god - bordering on zone X, especially if they are not diffuse but actually reflections on shinier skin, just like any other reflection. When I was talking about VII and VIII I was not talking about reflections.
Now I am sure that you will find situations and actual people where this does not hold true for the best image - just like anything else, there are exceptions to this rule as there are all rules. I just have no idea why all of the zone system related information out there uses the horrible example of caucasian skin being representative as a typical zone VI. Just a typical example at the top of the page - The window is the light source in this image the brightest areas are a mix of zone IX and X. The wall close to the window is a mix of Zone IX fading into zone VIII. The skin for the most part is Zone VII and VIII with a tiny bit of IX on the edge. Heck even the shadow on the breast closest to the window is Zone V and VI.
Hope this is at all useful.