From: Sandy King (sanking@clemson.edu)
Date: 07/21/02-09:11:31 PM Z
David Distefano wrote:
>using a b&w densitometer is there an easy way to get a good
>approximation of total density of a pyro neg?
>
>thanks
There is not a simple and universally correct answer to this question
because the issue is not just the densitometer but the exposing light
of the printing process as well. If you have a B&W densitometer you
may be able to approximate the stain density by taking the reading
through a blue-violet filter. A Schott BG-28 has been recommended for
densitometers with incandescent lights whereas a 47 or 47b is best
for fluorescent lights. However I suspect that either of these
filters will get you close enough, bearing in mind that the reading
is only going to be approximate in any event. I use a color
densitometer and have not actually used a B&W densitomemter in this
way but logic suggests that you will need to first read the filter
without a negative and then subtract that figure from all of your
readings.
Determining the density range of a pyro negative with this procedure
should get you fairly close to the effective printing density of
graded silver paper, but it will indicate a greater DR than is
actually the case with variable contrast silver papers.
With most of the alternative processes the actual effective printing
density range will be quite a bit greater than what you read through
a blue filer, or in blue channel with a color densitometer. In my
experience a stained negative that reads 1.4 with the blue channel
actually prints with an effective density range of almost 1.7. This
can be expected to vary somewhat with type of light source.
Sandy King
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