[pure-silver] Re: contrast changes
- From: Jean-David Beyer <jeandavid8@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Sun, 28 Feb 2010 07:59:20 -0500
Ralph W. Lambrecht wrote:
Shannon
One more thought. Exposure is the product of illuminance and time. By
opening up the aperture, you were able to keep the exposure time
consistent, but you increased the illuminance to provide the
increased exposure required to cover the larger format.
I have a Beseler color analyzer. I do not care to do color printing
anymore, but the thing works.
One use I have for it is just in situations like this.
I make 8" x 10" test prints, and use the same kind of paper (but
different emulsion numbers) for each size. When I get a print I like,
with the exposure I like, I measure the illuminance falling on the paper
with the analyzer, and then raise the enlarger head to get the size I
want for the larger print. I then open up the lens to get the same
illuminance. Since I use the same exposure time, this should correct
implicitly for reciprocity failure in the paper. Since I use the same
illuminance, this corrects for different enlarger height and
magnification ratio.
This procedure does not correct for flare in the darkroom affecting the
larger print differently, nor does it correct for any psychological
effects. In the past, with Kodak, Ilford, and Oriental Seagull, I have
not noticed much difference between different batch numbers of the same
papers.
--
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