Re: Van Dyke Toning
Jonathon Russell (Hylandscot@voyager.net)
Tue, 01 Jul 1997 08:56:33 +0000
Tom Ferguson wrote:
> In alt photo everything affect everything else. I too have noticed (and
> measured) an increase in contrast ("snap") in prints exposed by sunlight
> (about 1/6 to 1/3 stops or 0.05 to 0.1 density units in the plat/pallad and
> cyanotype I tested). I doubt this is due to "the old point-source vs
> diffused light situation", as we are contact printing. I would suggest
> that the sun probably has a different spectral "makeup" than UV fluorescent
> tubes. This difference seems (in my case) easily compensated for by
> controlling film development.
> Jadlupp@aol.com wrote:
> >Johnathan Russell commented on the differences in toning VD prints, and the
> >apparent effect of the light sources. Just as an observation, I have noticed
> >that the platinum and platinum/palladium prints, as well as cyanotypes, all
> >seem tobe "crisper", for lack of a better term, when exposed via sunlight vs
> >a uv light box. This is the old point-source vs diffused light situation, I
> >would guess.
> >Don Upp
> >Also in Michigan (where JR is )
> Tom Ferguson (firstname.lastname@example.org)
> Anti "Spam" return address in use, remove 2 "p"s from "pppipeline" for
> correct return address.
Your response, taken to its logical conclusion, seems to indicate that
we could change the contrast of some alt.proc. by changing the color of
the light source. I seem to remember reading long ago an old manual on
platinum printing that said to use blue glass in the contact frame to
increase contrast or to change the angle of the frame relative to the
sun for the same purpose. Any thoughts from the list?
I agree with you that since we are contact printing, the point light
source theory isn't valid.
Regards to all,
"Expose for the Secrets,
Develop for the Surprises!"