From: Carl Weese (cweese@earthlink.net)
Date: 12/01/01-08:35:55 AM Z
Judy,
The white card densitometry method in TNPP is adapted, with credit of
course, from you and PF.
Problems with reading pyro negatives:
blue channel of color densitometer should work, but the numbers will be
'abstracted' and not exact equivalents of non-pyro densitometry
b&w densitometer with blue filter *may* work if the meter's cell is
sufficiently panchromatic in response. May not be since it's not part of
the design parameter to read anything but density. (Getting cells to
mimick the color sensitivity of film was a major hurdle in the design of
modern exposure meters)
The Mantis b&w densitometer uses a bright blue lamp and seems to
'understand' stain density pretty well
If you make your own 21-step with pyro developed film, the two card
method may be workable, *if* our eyes read the stain the same as the
material to be printed on--not likely with UV sensitive materials. The
two card manual method may need a blue filter as well as a home-made
stained 21-step. I haven't investigated this.
As soon as I can get to it, I'm going to work up a matrix of
densitometer readings (with a Mantis) of shadow, mid-tone, and highlight
values of negatives I've already printed in platinum, and relate those
readings to formulas and exposure times. I think this will lead to a
chart that can be used to read new negatives and predict exposure times
and formulas for them (only in my lab, my materials, my coating and
processing, etc). Too busy making new pictures to do this right now but
it's on my project list.
---Carl
This archive was generated by hypermail 2b30 : 01/02/02-04:47:33 PM Z CST