What I mean by yellow trouble is not overall yellow cast of the print, although that happens occasionally as well, but least contrast or definition in the B channel. If you look at the RGB separations, B is the one with least "punch". I have learned to deal with it by curving, selective adjustments in the color stage, frequently with masks, etc. And yet I rarely mess around with RG separation and almost always with B separation. That's why I am excited about CMY (K=0) separations that I have been trying now.
As far as developing, you are correct that tunsten light introduces so much bias to the yellow layer. FOr the last few years I have been using warm fluorescent lights in my bathroom, which also serves as a developing area. I think that I have finally convinced my wife that having bath tub stained in beautiful magenta and cyan stains is the new home decorating trend.
Interesting comment about curves. I have perhaps as many or more curves for my former2200 printer. Most of them came from the period of trying to nail all the variables so precisely. I have a feeling if you have so many curves you actually know or feel what the correction should be and just make it as needed.
Beauty of gum is that whether you have a nice cureve, ugly curve, perfectly calibrated curve or no curve you can stil make beautiful prints.
> Date: Fri, 21 Nov 2008 09:49:26 -0700
> From: firstname.lastname@example.org
> Subject: Re: Re: separations for gum printing now curves
> To: email@example.com
> Henry and Marek,
> First Marek: if I read your post correctly, you USED to have problems with
> an all over yellow cast but now that you use a very flattening curve AWAY
> from the straight line, your prints are looking fine? Is that correct? OR,
> are you saying that STILL yellow is doing this for you? I assume also you
> are doing this curve on the negative, and the curve has the effect of making
> a very dense and dull negative? Making sure we are speaking apples to
> Henry, I agree. I wanted to get a handle on gum. That doesn't mean I am
> "tight" in my practice now tho. Sort of like finding the rules and then
> breaking them analogy. And celebrating the imperfections. One of my
> favorite Katrina images was a mistake--I had exposed a too thick black layer
> too short, and when I removed the print it all started running off in gritty
> grain. I looked at it and freaked and quickly laid it flat, pulled out a
> hair dryer and dried it so it wouldn't budge. That image is the starting
> image in my By Gum article in the Oct. 22 BJP. The image is on my website
> at the following URL, called Last Supper, the second one in. I can't tell
> you how many times my "mistakes" have turned into my favorite prints. So
> much for theory and perfection. All that dirt on the dishes etc. is actually
> gum grit.
> But anyway, back to curves. I just counted how many curves I have in my
> curve folder--107. A sign of a misspent youth? And that is after throwing
> out all my Epson 2200 curves when my printer went bust!
> I just went and looked at every yellow curve, and no matter what yellow
> (cadmium, arylide, azo, nickel, etc.) the yellow curve is a different beast
> and all are similar in shape, closer to the straight line but bowled out
> Even when I took a digital step wedge and side by side cut and pasted 8 of
> them with different curves, printed out one sheet of them, and exposed
> yellow, magenta, and blue, yellow was different than magenta and thalo.
> Magenta and thalo were similar enough to fudge. All inks.
> It is hard to have this discussion when people are using different
> calibration systems, different curve palettes (0-255, percentages, curving
> the positive, using black ink in the mix, using no black ink in the mix,
> using all inks in the mix), different workflows, etc., any one of these
> being a way to explain away differences in findings. But the fact that it's
> consistently the same in all my gum curves leads me to believe in **my**
> practice that it is a fact **I** can rely on, and thus I share it with
> others in hopes that we can build some sort of quantifiable knowledge.
> But whether that is any help to anyone else, who knows? But that you,
> Marek, struggle with yellow is no surprise as well, being the "outlier" of
> the bunch by my way of thinking.
> BTW, Marek, did I ever say on list that I never develop my yellows at night
> because under tungsten most of my screwups come with not judging my
> development time correctly with this color? The next day my print is
> usually too yellow. I suppose this wouldn't matter if you had fluorescent
> Christina Z. Anderson
> ----- Original Message -----
> From: <firstname.lastname@example.org>
> To: <email@example.com>
> Sent: Friday, November 21, 2008 7:23 AM
> Subject: Re: Re: separations for gum printing
> > Interesting to read the discussion on curves. My own engagement with the
> > PDN process was mostly motivated not by any desire for a photo-realistic
> > gum print, but rather a search for consistency in gum printing. I only get
> > to
> > print a few times a year, and I was fed up with reinventing the wheel or
> > making the same mistakes every time - so a process which pinned down
> > several variables while providing a lab-notebook reference for the future
> > was
> > what I needed to avoid quite so many discarded prints. For that it has
> > worked
> > admirably. Now it's possible to experiment with pigments ("what would that
> > look like with venetian red, egyptian blue and yellow ochre?") with the
> > other
> > variables a bit more under control.
> > On the other hand, I don't think the term "photorealistic" really applies
> > to a
> > gum print in any case, even one with "ideal" pigments, curves, and the
> > whole
> > works. A gum print is just a whole other kind of object.
> > best wishes
> > Henry
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