Re: negative density range determination

Joe,

The numbers vary because the actual exposure scale (ES ) of the
processes varies a lot depending on chemistry, working conditions,
paper, exposing light, etc. This is true with all processes, not just
cyanotype.

And the actual way people figure density range also varies, in the
same way that some people count Zones from II to VIII and others
count from I to IX.

In my own work I figure density range manually, i.e. by looking at a
printed step wedge, from the first maximum density to the first
density just over paper white. When I make this evaluation by looking
at a step wedge I simply count the number of steps and multiply by
log 0.15 (assuming a step wedge where each step represent
approximately 1/2 stop).

Some plotter programs may give different values because one can
choose IDmax, say at either 90% of Dmax or at some other figure. I
generally choose 90% of Dmax for Pt/Pd printing but a bit higher for
carbon printing.

The main thing is to apply consistency in your own work.

Sandy

>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 Mon Sep 13 06:58:40 2004