Ian, this is quite easy... once you select an exposure (using any method...) you know how many stops will we under or overexposed any spot in the image.
If you have 6 stops range you first have to decide at what zone you are to place your shadows, it can be Z-III or Z-IV depending on the detail you want to conserve in the shadows. Let's say that you place the shadows in Z-III, then your highlights will be in Z-VIII or in Z-IX, depending on how you calculate your 6 stops range.
You shoud always expose enough to preserve your shadows, then it can happen that you burn your highlights, Z-IX can be too much... but you solve that with development !!!! So with a high range scene you expose to preserve the shadows and then you develop less to prevent burning the highlights. Well, we have the highlights in the Z-IX, we may want it in Z-VII, so 9-7 = 2, an N-2 development plaves your highlights in Z-VII !!!! Solved !
Note that N-2 development does not modify much the shadows, while it limits the excessive density in the highlights.
So this is the classic recipe for a high dynamic range: expose to have your shadows in Z3 or 4, then develop less to place the highlights in Z7 or 8. Using Z3/4 or 7/8 depends on the film you use an on the detail what you want to obtain.
This is for negative film... slides are another animal.
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