<<<I exposed film in sets of three with step tablets and
developed to a range of final densities. One group I left alone, from
one
group I removed the stain, and from one group I bleached the silver. >>>
The problem here is that you are not testing for the relevant question,
which is how the group "left alone" differs from negatives given
standard non-staining development. The stain/silver relationship within
the pyro negative may be proportional, but that doesn't mean that it is
proportional _to_ the densities of a negative developed in, say, HC110.
And *that* is the question that needs to be answered to know whether
pyro gives a usefully different curve from other developments.
So far, I know that pyro gives HP5+ a dramatically different curve (for
Pt/Pd) than it gets from several traditional developers, and that the
new curve is very useful. HP5+ has a heavy fb+f and a resolute shoulder:
it may well be that films like FP4+ and TXT which have thin fog levels
and little or no shoulder will show much less variation with a pyro
development. I'll be testing for that soon.---Carl