U of S | Mailing List Archive | alt-photo-process-l | Re: Gum calibration (was: Paper negatives- Ink Selection)

Re: Gum calibration (was: Paper negatives- Ink Selection)

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  • Subject: Re: Gum calibration (was: Paper negatives- Ink Selection)
  • From: Loris Medici <mail@loris.medici.name>
  • Date: Sat, 18 Oct 2008 09:50:41 +0300 (EEST)
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It's not about curves Katharine, why you insist that much to NOT
understand what I'm saying? I'm talking about PRINTER / PAPER PROFILE,
INKS, NEGATIVE COLOR and most importantly, the specific DENSITY RANGE
which one can get from that combination here, since from the start. No
twisting please. Whew!

Besides, we have a comprehension problem here: Mark says that in condition
of "...providing all other variables are equal...", now, we're comparing
exposure time where dichromate concentration is similar, lightsource is
similar, negative substrate, paper, gum and stock gum solution strengths
are the same, what is considerably different between Keith and I (which
you are ignoring) here is the printer (therefore paper profile & inks) and
I'm completely sure that Keith's negatives DR are greater than mines and
if he calibrates for a lower DR, he'll get shorter exposure times...
Designing a curve will be just a side bonus.

OK, I decided to take another road, since the people doesn't get it with
the current one: Keith, can you please send me a small image (say 4x4" @
300dpi, 16bit grayscale) privately, if you like? I will make a negative
for you from that one and send it to you allowing you to test it (along
with the negative you personally made from that file) and see what
happens? (Or, you can just have it measured with an UV densitometer - that
also will give an idea...)


18 Ekim 2008, Cumartesi, 3:25 am tarihinde, Katharine Thayer yazmış:
> Keith,  I've said this before, but since it keeps coming up I'll say
> it one more time:  if your goal is to reduce exposure times, this
> isn't the most fruitful place to look IMO.
> Mark has pointed out that exposure time isn't a function of printer,
> ink type, ink color or printer settings:
> ender100 wrote:
>  > Exposure time does not depend on the printer, ink or color of the
>  > negativeâ&#65533;&#65533;it merely depends on the substrate you are
>  > onâ&#65533;&#65533;providing all other variables are equal.
> and logic says that exposure time can't be a function of curves,
> since the exposure time is established before the curve is
> calibrated, and doesn't change after the curve is calibrated.
> Exposure time is a function of a lot of things such as light source,
> dichromate concentration, pigment concentration, paper speed,
> environmental conditions; how the negative is generated is not a
> significant factor, in my experience.
> Katharine