Hi Katherine,
No—I don't mean you can pick a process and plug in some "gum algorithm" or
"Palladium Algorithm". The PDN system is all OUTCOME BASED, so every variable
is accounted for, providing you can control them. I agree that gum has more
variables than say Palladium—because you have "mechanical" development issues
to contend with. One person may do "photographic development", the next
person may tickle it with a feather, and another might hose it with a fire hose
and then slap it against a brick wall. Some even brush off emulsion to get the
final image they want. Given all that, there is still some value in
calibration and developing curves specific to a process. I have seen Chris
Anderson's calibrations with gum and they are repeatable. It is also quite
interesting how the adjustment curve varies for her Yellow Layer of tri color gum vs
the Magenta Layer—and those curves are fairly consistent. So, who cares?
Well, for me, I like to have a constent, home base, if you will from which I can
ventur forth to experiment and play with until I get the image I want. It
ain't a formula and a bunch of numbers in the end. All these processes have a
lot of serendipity (fancy word for screw-up?) and room for artistic
expression. I still use a light meter when I take a photograph—but that knowledge
gives me better control and more artistic freedom. The cheapest and most
interesting photographic tool one can buy is a 31 standard step tablet.
Best Wishes,
Mark Nelson
www.PrecisionDigitalNegatives.com
In a message dated 12/1/05 1:53:02 PM, kthayer@pacifier.com writes:
>
> On Nov 29, 2005, at 11:29 PM, Ender100@aol.com wrote:
>
> >
> > If you match the density range of the digital negative to the
> > exposure scale of the alt process before you build the curve, you have
> > won half the battle. Then the curve doesn't also have to adjust for a
> > mismatch of exposure scale and density range.
>
> Ah, that perhaps answers my question. I was wondering, last night,
> whether you *really* meant Exposure Scale to mean one specific number,
> which would indicate "the" number of steps that a particular process
> will print, and then decided I was too tired to deal with it, so I
> didn't ask the question. This response above, using the definite
> article ("the" number of steps that a particuar process will print")
> seems to suggest that yes, you do mean that for any process, you
> think that there is a number called "Exposure Scale" that can be
> plugged into the curve-mapping algorithm; any curve for that process
> will generate that many steps in the final print?
>
> If this is so, and if you mean to include gum in the processes that can
> be so neatly plugged into the algorithm, then I would have to
> disagree; while the average number of steps is five or six, the number
> of steps (Exposure Scale if you will) will vary widely, depending on
> the dichromate concentration, the pigment chosen, the pigment
> concentration, the skill of the printer, the aim of the printer for a
> particular printing, the exposure/development balance, and so forth.
> It seems to me that you would have to use a different exposure scale
> and a different curve for every single printing, unless you used the
> same pigment at the same concentration and held everything else
> constant for every printing you ever did. For someone like me, who has
> a different "look" in mind and takes a different approach to every
> project I do, this wouldn't make any sense. I just prefer to use the
> same ordinary negatives and vary the printing to get the different
> looks I want, rather than developing a different curve for every
> printing. But this is another example of the many different ways there
> are to in gum printing to skin a cat.
>
> And then there's the point I raised yesterday or the day before,
> cautioning against confusing the number of steps with tonal range of
> the print. In gum, the number of discernable steps has little to do
> with tonal range. In silver (or platinum, I presume) you can relate the
> exposure to the number of steps to density to the tonal range; they are
> all related in a lawful way. In gum, none of these laws apply, as I was
> trying to explain to Yves the other day (and will make another stab at
> making this point more comprehensible this morning).
>
> For example: Yellows, as someone pointed out recently, tend to give
> steps that are closer together than darker colors do. The steps you
> get with a light pigment mix and a high concentration of dichromate
> are IME closer together (more subtle tonal gradations) than the steps
> you get using a medium pigment concentration and/or a lower
> concentration of dichromate. And so forth. So not only do the
> different pigments occupy different parts of the tonal range, but if
> you expressed the difference between the lightest and darkest tones
> quantitatively, I believe the tonal range would often be different
> even when the same number of steps are printed. But more about all that
> in another post, later.
>
> I said yesterday that there are two ways to approach the problem of a
> mismatch between what the gum will print and the density range of the
> negative: (1) reduce the density range of the negative, or (2) print
> multiple exposures to increase the tonal scale of the gum. Again, I
> don't think there's a right answer to this; each person will have a
> personal preference. I personally haven't been very attracted by the
> prints (reproductions, admittedly) that I've seen of one-coat gum
> prints that have been made by the process you seem to be describing, of
> smooshing all the tones in a longer-range negative into a curve to fit
> the short printing range of gum, however you want to define or label
> that range. To me (and again it could simply be an artifact of poor
> reproduction, or the curve wasn't developed in as sophisticated a way
> as you are doing, perhaps) these prints simply aren't very
> interesting, and I personally prefer a gum print with more tonal
> range and more depth to it. But, each to his own,
> Katharine
>
Mark Nelson
Precision Digital Negatives
Received on Fri Dec 2 00:03:49 2005
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