From: Sandy King (sanking@clemson.edu)
Date: 08/31/01-04:41:49 PM Z
Manuel Gomes Teixeira wrote:
>I was
>interested in obtaining negatives that could be printed in both contact
>methods Pt/Pd, Silver POP and with conventional VC paper for enlargements.
>Nevertheless I was intending to use other developers than Pyro but after
>reading your post I'm quite pessimistic about it.
In spite of its limitations it is still very possible to get enough
contrast for POP printing with BPF. I can get a DR with this film in
normal lighting conditions (SBR 7) of about 1.6-1.9 with either ABC+
or Pyrocate-HD, which should be more than enough for most POP
processes. If you are shooting in low contrast situations, however,
you will not be able to approach this kind of DR without increasing
the films b+f.
BTW, if you are getting very high b+f with ABC+ something is wrong
with the developer or film as this combination gives me negatives
with a b+f of about 0.25, not real low but not unreasonably high
either. You may be over-exposing. I rate BPF at an EI of 150.
Remember, if you increase development times to get a high DR you
should also increase the EI of the film somewhat as the extra time in
development will give you an increase in effective film speed so if
you are basing your exposure on a shadow density and developing for
about 2X normal time I recommend you increase the EI of the film to
about 250.
Finally, what is your exposing light for POP. In spite of everything
I still sometimes get negatives that are too dense for printing with
my artificial light source (BL tubes). Try direct sun with this type
of negative. I have some negatives that are so dense that they will
not print with the BL tubes even with 4 hour exposures, yet they
print beautifully in direct sun in 30-40 minutes. As a rule I find
POP about three times as fast at my BL tubes for POP processes. That
is, an exposure that takes 5 minutes with the sun will take 40
minutes with the BL tubes.
Sandy King
Fi
f around .25 (not low, but not unreasonably high
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