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?)

24 Ekim 2008, Cuma, 11:18 pm tarihinde, Katharine Thayer yazmış:
>> Hi Loris,
>> Maybe but,
>> All my pigments are diluted 15ml to 150ml paint to gum. Any less
>> and they get very wishy washy (insipid).
>> David
>> 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?

> 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?