Re: negative density range determination

I haven't heard from anyone yet regarding the question I asked yesterday
so I am repeating it here (below) with a bit of example data culled from
several texts. Various authors are recommending the following density
ranges for cyanotype:

Schaefer:1.60
James:1.40-1.60
Crawford:>1.60
Farber: 1.40 (and 1.8-2.6 for Ware's)
Barnier: 0.95-1.4 (and >2.0 for Ware's)

The range given for Salted Paper is:
Schaefer:2.00-2.40
James:1.50-2.00
Crawford:>1.70
Farber: 1.60-1.80
Barnier: 1.80-2.00

So, you can see recommendations vary considerably. Additionally, the
way the authors determine these numbers also varies.

For example, James refers to the negative density range as the
difference between the densities of "the densest highlights with detail"
and the "thinnest shadows with detail."

Crawford states the negative density range is that which prints "the
full range of tones from 'paper white' to the 'maximum black''' and that
the exposure range is equal to the difference in density between "the
minimum exposure to produce the first perceptible tone and the exposure
necessary to produce the deepest possible tones."

Farber states the negative density range is "the difference between the
brightest highlight and the deepest shadow with some texture."

To me, there is a difference between a density producing a tone (e.g.
Zone I & IX) and a density producing some texture (Zone II & VIII for
slight perceptible texture and zone III & VII for full texture) as well
as maximum and minimum values. But, these authors' definitions seem to
be measuring different values and reporting vastly different ranges.

So, I ask again what is the standard for determining negative density
range (if there is one) and what sort of target ranges do various
practitioners on this list use for the processes listed below?

Thanks again for any info from actual practice.

Joe

>>> jsmigiel@kvcc.edu 09/08/04 12:17 PM >>>
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 Thu Sep 9 19:05:04 2004