Re: Why multiple exposure (was Re: (Gum) Tonal scale)

On Dec 1, 2005, at 11:46 AM, Loris Medici wrote:

> I have to mix a standard emulsion (same amnt. Of pigment / gum and
> dichromate) in order to calibrate with the PDN system. Everything has
> to be
> as constant as possible. I just added gum to the tube pigment until the
> saturation and density seemed right to me (not too dark and opaque,
> not too
> light).

Hi Loris, again,
I hadn't paid much attention to your test before, as I said, since
these kinds of tests make my eyes glaze over and because I know zip
about PDN (except that it costs $75) and there are people here who
know it well. But your subsequent comments made me go back and look at
it again, and now I do have a couple of comments/questions.

I have a question about your description of the "standard emulsion"
above. If the standard emulsion means standard for a particular pigment
mix, just making sure it's exactly the same each time, then I'd say
that's great. I think mixing by eye is great (it's the way I mix) and
you found a good mix that prints well just by using your eyes, which is
the best way I've ever found to get the best mix for a particular
pigment.

But if "standard emulsion" means that for every pigment you use, you
use the same amount of pigment, gum and dichromate, then I'd say that's
not such a good idea. So I hope it's the first and not the second. I
just need that clarification.

On Dec 1, 2005, at 12:34 AM, Loris Medici wrote:

> BTW, what I trying to achieve is to standardize my pigment + gum +
> dichromate emulsion mixes and exposure time for each color, so that
> they
> all give me the same number of steps. Only after managing this I will
> start to build curves and attempt to make tricolors. (Not that I feel
> an
> urge to do tricolor gums - just for its fun...) What do you think about
> this strategy?

I think Chris already suggested not using this approach for other
reasons, but I would discourage it because you will find that the
different pigments will print a different number of steps and there's
just not a lot you can do about it. I don't think your yellow,
especially since it's PY154, a light-valued azo, will print as many
steps as your pthalo. I don't think you would want to deliberately
shorten the range of the pthalo to match the yellow, just for
calibration's sake, would you? So I think this approach, since you
asked, wouldn't be a productive approach to take.

You're doing great----
Katharine
Received on Fri Dec 2 15:48:09 2005