From: Sandy King (sanking@clemson.edu)
Date: 08/31/03-01:05:32 PM Z
Jacques,
When I first started making digital negatives I just got the image to
what I wanted it to look like on screen, applied one of the curves
from Dan Burkholder's book CD, and printed it. Luckily the negative
turned out to have a density range about right for my process, as I
was able to verify by actually printing it. Since then I have
developed another curve for my processes based on Mark Nelson's
method and negatives made with this curve print almost perfectly. I
also measure the density range of my negatives with a UV reading
densitometer and can verify that they have a log density range of
about 1.8.
Log value is a sensitometric term that can be translated into stops.
A log value of 0.30 equals one stop, log 0.15 equals 1/2 stop. Pt/Pd
as a process has a log exposure scale of about 1.65 - 1.80, which
could also be stated to be a range of about 5.5 to 6.0. So to print
all the tones of a negative you need to have a negative density range
of about 1.65 to 1.80 to match the ES of Pt/Pd.
Sandy
>
>Sandy,
>
>in your last post you say (quote) Both processes require negatives
>of the same density range (about log 1.65-75) and the final images
>of the two processes are for all practical purposes identical in
>terms of color and tonal range.
>
>I am about to start pt/pd printing, but I am still struggling on the
>measurement of density ranges for (digital) negatives. people on the
>list come up with log. ......, but how can I find out (or change)
>what the log of a specific (digital) negative is. I have been
>reading through Dan Burkholder's book and also John Barnier's Coming
>into Focus, where actually on page 233 several curves are given in
>D-max, but somehow there is a gap in my brain translating these
>figures into common sense (i.e. a correct curve for e.g. pt/pd
>printing).
>
>Maybe you can just cast the right light on my missing link.
>
>Thank you.
>
>
>Jacques Verschuren ABIPP ARPS QEP
>Fotografie Jacques Verschuren
>Ronduitsestraat 2
>5443 BC Haps (N-Br.)
>The Netherlands
>T. + 31 485 331210
>F. + 31 485 318569
><http://www.jacquesverschuren.nl>www.jacquesverschuren.nl
>
>-----------------------------------------------------------------------------------------------------------------
>12¸ years of photography in
><http://www.jacquesverschuren.nl/milestone.htm>www.jacquesverschuren.nl/milestone.htm
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