Thanks for this. Great post.Basically you are correct here.
You might wish to get or make a Zone System sticker for your light meter or get a Zone Dial. Then you just place the shadow reading on the Zone you wish it to be in; no bothering with underexposing by one (for Zone IV) or two (for Zone III) stops. See here for downloadable stickers/Zone dial: http://www.darkroomagic.com/DarkroomMagic/Camera.html
In any case, once you have determined your shadow placement, that is your basic exposure, regardless of whatever development scheme you choose later. You "place" the shadow where you want it, and then see where the other important values in the scene "fall."
If you are shooting roll film, which I surmise you are from the aperture/shutter speed combinations you give, then don't worry about plus or minus developments. Those were intended for sheet film users who can develop each sheet separately, or for those who really want to carry around extra film backs/camera bodies for plus and minus developments. When I shoot roll film I just place the shadow, develop "normally" and use paper grade to deal with contrast. This works fine for many subjects of different contrast on one roll.
If you do wish to have plus and minus developments, then here's how you deal with them: After determining your shadow placement and basic exposure, see where the important highlight value falls: If you need to move a subject that falls in Zone VII to Zone VIII, then you indicate N+1 development, make the necessary exposure adjustment (I underexpose 1/3 to 2/3-stop for N+1 depending on the film/developer combination) and shoot away. The opposite if you need to move a subject that "falls" in Zone VIII down to Zone VII; then you indicate N-1, make the necessary exposure adjustment (I overexpose 2/3-stop for N-1 with most films) and shoot away.
Now, if you insist on doing this without a Zone System sticker on your meter, you need to count stops from your shadow exposure, which can get a bit confusing. However, let's go through scenario 1 above:
~ Let's place a shadow on Zone III. Let's say the meter reading for the shadow was f/11 at 1/15 sec. You want that in Zone III, so you underexpose two stops from that; let's say f/11 at 1/60th sec. That is your basic exposure, but isn't used for what follows, Remember it, write it down, or whatever, but go back to just reading the meter for the next step.
~ Now meter the highlight. Let's say it reads f/11 at 1/250 sec. (keep one of the parameters constant so it's easier to count; here f/11 is constant).
~ Now here we go, 1/15th sec. is Zone III (that was our shadow reading, not our basic exposure), so f/11 at 1/30th "falls" in Zone IV, 1/60th in Zone V, 1/125 in Zone VI and (whew, we've finally arrived...)1/250th sec falls in Zone VII. Now you know where your highlight (metered at f/11; 1/250) falls.
~ We decide we really want that highlight to be lighter in the print than Zone VII, say Zone VIII, so we indicate N+1 development.
~ Now, go back to your basic exposure (remember that, it was f/11 at 1/60th sec.), underexpose your predetermined factor for N+1 development (let's say 2/3 stop) and you arrive at f/16- (1/3-stop wider than f/16) at 1/60.
~ Now decide what aperture/shutter speed combination you really want; let's say we need more depth-of-field for this shot, so we stop down to f/22- and change the shutter speed to 1/30 to compensate.
~ That's all there is to it... Set that on your camera and take the shot.
All this is predicated on having made tests to determine you own personal E.I. and development times, of course.
Hope this helps,
Just curious about your printing methods. Do you use fixed grade papers or variable? Do you ever use split grade printing or just stick to the one grade ?