On Thu, 1 Dec 2005, Katharine Thayer wrote:
> ... My point about the unpigmented gum was to emphasize that
> while the pigment does provide the tonal scale, it does not participate in
> the reactions which constitute the response to exposure, so unlike silver
> printing and many other photographic processes, with gum you cannot draw a
> curve relating exposure to *density of reaction product* to tonal scale.
Actually this calls to mind an expression I've used in trying to explain
the process -- I say the action is the gum, dichromate, etc, and "the
pigment is just along for the ride." But in fact, it occurs to me that
the character of the passenger can make a large difference also -- if he
weighs 300 pounds, if he keeps opening all the windows, if he throws rocks
at the bicycles passing by, etc. (Or "she," of course.) That is, we do
know that the particular pigment affects behavior -- even if just its
opacity.
As for "curve," I generally flatten the neg to no more than the emulsion
will print & then proceed by eye... too many variables to get hung up on
"curve," or beyond me, anyway.
J.
Received on Fri Dec 2 01:02:50 2005
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