U of S | Mailing List Archive | alt-photo-process-l | Re: Gum Calibration 2 (How to read color samples?)

Re: Gum Calibration 2 (How to read color samples?)

Hi Loris,

Maybe but,

All my pigments are diluted 15ml to 150ml paint to gum. Any less and they get very wishy washy (insipid).


On Oct 24 2008, Loris Medici wrote:

David, could it be that the pigment concentration is too much?

Greatly unlikely at those concentrations, IMO.

Hello Katharine,

Is that for my question to David or David's answer to it?
Oh sorry, too cryptic. I meant it's unlikely that David is using too much pigment for tricolor, at the concentrations he's describing, and I'd say that's true for about any pigment he might possibly be using.

> But I have to agree
> with David; that's what I've seen again and again, that often when
> people calibrate their layers individually they then find to their
> surprise that such calibration of the separate layers doesn't sum to
> a perfect tricolor print, from any number of standpoints.

What could be a better way to do it? I felt I was in the right direction;

1. Choose the right pigments (my choice seem to be foolproof - as I'm
using either the main secondary colors (for cyan PB15:3 and magenta PV19
Rose) and a yellow very close to the ideal (same hue angle, but slightly

2. Balance the pigment amounts (my current start point is 1+3 PY151, 1+5
for PV19 Rose and 1+7 for PB15:3) so that none will overpower the

3. Test by calibrating each individual color first and then print them (as
21-step tablets) on top of each other (hoping to get a neutral result in
each step) later, inspect and dilute more (proportionally, trying to
balance any shift from neutral - if present) until black is convincing
black, middle gray is middle gray and highlights are highlights.

Does it sound good to you?
Since I was recommending a three-dimensional approach, and that appears to be what you're doing (aiming for neutral in the three layers together) it sounds good to me. I'll be interested to hear how this works for you.