U of S | Mailing List Archive | alt-photo-process-l | Re: (Drumroll): gum prints w curved vs uncurved negs (Re: How manygum

Re: (Drumroll): gum prints w curved vs uncurved negs (Re: How manygum layers (Re: ferri sesquichlorati)


> (An offlist
> correspondent thought I must be applying the curve to the negative
> rather than the positive, but that's not the case).

I can't speak for ChartThrob, as I've not tried it.  But generally
speaking, you want to curve the negative, not the positive.  Have you
tried making a test print with the curve applied to the negative?

> Someone wrote a while back to say that when
> they use PDN with tricolor gum, the print comes out too dark, and
> wondered what they were doing wrong; the answer was something like,
> "Oh, yeah, that's what always happens,"  the recommendation being
> that the inquirer just play around with variables, I forget whether
> it was pigment concentration or exposure, by trial and error until
> they find something that works, using the same curves.

If this is the case, they didn't correctly use PDN.  I can tell you from
experience that the only time my PDN'ed gum prints have been too dark, or
too light, or too conrasty, or not enough contrast, etc. it's been a
poorly calculated curve.  Running through the calibration process again
always solved the problem.

>And then it
> turns out that after all one doesn't use a different curve for
> different pigments, as has been claimed here much in the past; one
> just uses the same curve and varies the exposure (which kind of
> messes with the idea that the curves are supposed to be based on a
> standard printing time, doesn't it?).

Again, incorrect use of PDN.  Each pigment does "require" its own curve;
this is especially aparent in curves for yellow pigments, where it doesn't
follow the standard "s" shape that most others do.

> So I'm inclined to think that there's not much difference between
> what we're all doing; whatever kind of negative you start out with,
> you still have to master printing gum,  and no matter what kind of
> negative you start out with, you're still going to be "fiddling with
> it until you get what you want in the print."

Well, mastery of process is a given, no matter what you're working on. 
But in my own experience, curves have made a tremendous difference.  So
I'm going to have to gently disagree with you there.

Camden Hardy