From: Sandy King (sanking@clemson.edu)
Date: 07/25/02-09:14:26 AM Z
Carl Weese wrote:
>
>I've done very little enlarging from pyro negatives. I've used Tri-X and
>D76 for my 35mm work since the 1960's and see no reason to switch. With
>large format negatives intended for Pt/Pd printing, *maximum* staining
>is not what you look for. You want just enough stain to give the desired
>contrast boost, without picking up overall stain that prolongs printing
>exposures without improving print quality.
I agree completely. Maximum staining means that you will be picking
up an overall b+f stain that serves no purpose other than
contributing to longer printing times. A pyro stained negative should
have a b+f reading of only about 0.02-0.04 more than a negative
developer in a non-staining developer. In order to keep the b+f stain
as low as possible I recommend:
1. Don't use the alkaline after fixer rinse. This rinse adds very
little image stain but a lot of useless general stain.
2. When developing for N+ contrast consider using a stronger dilution
rather than increasing the exposure time. You may find, for example,
that a 2:2:100 dilution of PMK with 10 minutes of development time
will give you the same CI as 20 minutes of development with PMK at
1:1:100, but with much less general stain. This is because with most
pyro developers there is a big increase in general stain from
oxidation caused by developer exhaustion.
3. If in spite of the above you are still getting high b+f levels
consider adding a small amount of potassium bromide to the developer.
Test by mixing a small amount of a 2-3% solution of potassium bromide
and add this to the working developer at the rate of about 5-15ml.
For the record, both ABC+ and Pyrocat-HD already contain potassium
bromide but PMK does not.
> It's also important that the
>visual stain isn't what counts: the key thing with alternate processes
>is how the specific print medium responds to a particular stain. To
>someone used to PMK, negatives processed in Pyrocat HD seem to have
>almost no stain at all, yet they print in Pt/Pd or in carbon with the
>same response as PMK negatives that show far more stain. What the eye
>sees isn't the same as what the UV-sensitive paper sees.
Very important point. When working with stained negatives in all of
the alternative processes I am familiar with the visual appearance of
the stain is not a reliable predictor of printing density. For that
matter even a regular color densitometer will not indicate a reliable
printing density. I have some FP+ negatives that were developed in
Pyrocat-HD and visually they appear to have no stain at all but they
print with a very high effective density range.
Sandy King
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