Pyro Developers

Before this thread was subverted the discussion was focused on pyro
developers for alternative processes.

Most of us would agree that apparent image sharpness on the print is
determined by a chain of events, beginning with film type,
continuing with optical quality and method of exposure, on from there
to choice of developer and type of development, finally culminating
in printmaking.

I have for a long time championed the use of certain pyro staining
and tanning developer because I have found them to be sharper than
other developers. Yes, the differences are in some cases very small
but the weakest link in the printmaking chain is the first one to
fail so I think it makes sense to make the sharpest negative possible.

So, how to resolve the question of whether certain pyro developers
give sharper results than traditional MQ developers?

Do this test.

Here is the comparison. A pyro developer (Pyrocat-HD 1:1:100) with
a very popular MQ developer (D76 1:1.)

1. Using the same camera, same settings and same roll of film we
make exposures of a given standard. I suggest the Edmund Scientific
Resolving Power Chart #83001, same as the 1951 USAF Test Pattern,
spaced at a distance to approximately fill the finder.

2. Split the test film in half and develop one part in Pyrocat-HD
1:1:100, the other in D76 1:1. You should determine in advance the
development time for a given CI for the two developers since any
comparisons of sharpness must be calibrated to equal contrast on the
negatives.

3. Examine the resolution of the two negatives with a microscope at
about 40X magnification.

See the point? With any film the Pyrocat-HD negative will resolve
about 10-15 lpm more than the D76 negative. Same would be true of
other commonly used MQ developers such as HC-110, DK-50, etc.

Note, however, that all pyro formulas do not give equal results.
For example, Pyrocat-HD and PMK, which are true high definition
develops, are considerably sharper than Rollo Pyro and ABC Pyro.

Sandy King
Received on Sat Apr 3 23:07:32 2004