Re: (Gum) Tonal scale

On Dec 1, 2005, at 11:02 PM, Judy Seigel wrote:

>
> 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.

Which is what I keep saying. Or maybe you're just writing to say you
agree with me, but every time I agree with you, you write back to agree
with me again, which makes me think that you think we are debating
opposite sides of an issue. My whole point is that tonal scale is a
function of pigment and pigment concentration, (mainly, but along with
a host of other things) and so if everything else is held constant,
every pigment and every concentration of that pigment will give a
different tonal scale. Yes, pigment affects behavior, very very much,
that's exactly what I'm saying.

My whole point, and my only point, throughout this discussion, is that
the relationship between tonal scale (since it is made of pigment which
does not participate in the reaction) and response to exposure, (since
it is the production of transparent crosslinked gum) is an indirect
and largely unknown (in a quantifiable sense) relationship, and so
can't be graphed to read tone from density of crosslinked gum, as
someone wanted it to. How many times would I have to say that, I
wonder, before people started understanding what I'm saying.
Katharine
Received on Sat Dec 3 12:57:51 2005