Expanding or contracting B+W developement time

[john_c.]

What's a simple way to remember how to instruct the lab regarding

other-than-normal B+W developement? I haven't shot B+W in a while. To

reduce contrast, is it N-1, N-2, etc.? To increase contrast, is the

instruction N+1, N+2, etc.? I know how to spot meter, and I know the

zone system; I've just forgotten/confused the - and + designations.

[david_hedley]

N-x to reduce contrast (e.g. if the dynamic range of what is important in the image is outside Zones III - VII). As the development time is being contracted, maybe by 10-20% for N-1, exposure is normally increased (by 1 or 2 stops, maybe) to keep substance in the shadows. (In other words, rate the film at a lower speed).

 

N+x to increase contrast (e.g. if the dynamic range is very limited). I normally also rate the film between 2/3 to 2 stops faster, as the development time is increasing - possibly by 30-40% for N+1.

 

Using the above in practice means understanding where to place values for the important shadow areas, where the highlights will therefore fall, and how both shadows and highlights will be proportionately affected by expanded or contracted development. Ansel Adams' "The Negative" is simply the best guide available to this.

 

I have so far found TMax100 to be the most flexible tool to work with in terms of altering both film speed rating and development to manage the contrast of the image, and I normally develop in Rodinal. I'd like to try PMK Pyro, but I can't find a source in Tokyo. I would be interested in others' opinions on black and white film & developer combinations. Regards