negative density range determination

As a result of some recent testing of cyanotype emulsions I have a
question regarding reported optimum negative density ranges for the
various alternative processes. As I read through several texts and skim
past threads related to the subject on this list, I realize there is
wide variation in the actual range numbers reported as well as how these
figures are determined by individuals (and not everyone reports their
method).

My take on the subject is that the range should be determined by
subtracting the negative density of a slightly textured shadow area from
the negative density value of a slightly textured highlight area. In
Zone system terms, I would subtract the net density of Zone II from Zone
VIII.

Is this standard? Are there good/valid reasons to use a different pair
of numbers/zones in the calculation (e.g., Zones III and VII, or Zones I
and IX, or initial densities producing max black and paper white)?

I would appreciate input on how individuals on the list determine the
density for various processes and also what target range values you use
for the following processes: gum bichromate, cyanotype, van dyke brown,
salted paper, Kentmere/Centennial POP, and albumen printing.

Thanks for any data and/or method you care to share.

Joe
Received on Wed Sep 8 10:24:26 2004