Re: GCR and UCR

Katharine wrote:

> First of all, before I even go on to read the rest of this

And in another post,

> Of course I meant that it is eminently POSSIBLE to make black using
> only color, as any painter knows and as has been demonstrated for
> years by tricolor gum printers.

Katharine, I'm disappointed. I would never have expected that you would be
one to react with dogma and without reading a whole post. Isn't the point
of the list to dispel myth and get to the unvarnished truth? I did not say
you were wrong as a practical matter, and in fact I agree that the results
one can get from tri-color gum can be stunning. What I said was that I
thought the actual situation is more complex than either you or the people
you were responding to had articulated. Both of the issues you took
particular exception to (in my previous post) were addressed in the
original, if you had bothered to read it before replying. My two points
were simple:

1) Whatever problems lithography has, layered gum also has TO SOME DEGREE,
purity of the pigments notwithstanding. This is a direct result of two
facts: first, that pigments in a gum print both filter light in a
transmissive manner (just like the dye layers of a C-print) and at the same
time reflect light. And second, that no naturally-occurring pigments form
an ideal tri-color system. The comparison to mixed paints is not apt --
mixed paint is homogeneous and opaque, while gum prints rely on the
transparency of heterogenous layers.

Not being a painter, I can't say from experience whether it is possible to
mix tri-color pigments to a convincing neutral with no ... now I've
forgotten the twenty-five cent word for color shift under different
lighting conditions. My hunch is that one can satisfy most practical
artistic purposes, but that color densitometry would show differences as
compared to charcoal black and careful scrutiny by eye would, as well. But
that's just a hunch. And even if it is possible to get a perfect neutral
with mixed paints, that result does not directly answer the gum question
for the reasons given above. (Also, it is my understanding that painters
do not generally start with tri-color pigments when they mix black, so what
may be possible with other pigments may not be with tri-color pigments.)

I'm curious about mixed-pigment D-max, and would be interested in hearing
from painters whether mixtures of the popular tri-color pigments can match
the D-max of a good charcoal black.

2) Because of the reflective nature of pigments and the fact that the gum
layers need to be semi-transparent for the process to work, the deepest
neutral one can hope for will be less dense than can be achieved with a
true black pigment. I assume you will agree that the D-max of tri-color
gum is around 1.4 at best, whereas 1.7 is not hard with Pt and 1.9-2.0 is
possible with either carbon or dye transfer (as well as toned
silver-gelatin), and I suspect with a carbon-black gum layer as well. THIS
DOES NOT MEAN THAT YOU CAN'T MAKE GOOD ART WITH A D-MAX OF 1.4. However,
if someone DOES want to make color gums with a higher D-max, (s)he will
need to use a K layer, and some version of neutral substitution or neutral
augmentation will be good for that person to know.

Best regards,

etienne
Received on Wed Sep 15 20:58:25 2004