Michael,
I covered this issue of UV contrast between two different colors of ink which might cause exagerated "ink grain" in the print in my book about 5 years ago. There is a palette included which helps test for it. It also varies with which alt process you are using.
--
Best Wishes,
Mark Nelson
On Apr 9, 2009, at 1:31:37 PM, "Michael Koch-Schulte" <mkochsch@shaw.ca> wrote:
That's interesting Clay -- and thank you. I observed this "grain" effect
too when printing out the RNP Arrays. But it never dawned on me that
similar contrasting ink carts would produce smoother highlight tones. A
nice bit on info and a compelling reason to use QTR. I think I know,
but for the record which did you start pairing together? The magenta
pairs and the cyans pairs? I just learn to observe the "problem" areas
on my colour tests and then avoid using the grainy "paths" as choices
for negative colours. To answer Loris' question : it's a wavelength
filter effect pure and simple. Certain coloured negatives will absorb
emitted light better than others colors. It's a dance between the light
source colour and the negative colour. The proof of this can be had
comparing exposures made in the UV box compared to the light from the
Sun, then compare this to a tungsten source. UV is on the "blue" side of
the colour spectrum. What kind of filter do you use in BW photography to
make your sky go dark? Yellow or Green will turn a blue sky from dark to
black.
~m
Clay wrote:
> FWIW, it is very instructive to print out the QTR ink limits test and
> graph the UV transmission density versus ink percentage for each ink
> on a single graph. When I did this for my printers, the 'aha' moment
> came when I realized that certain combinations of ink colors are going
> to be more prone to the graininess effect that is sometimes observed
> in the highlight areas of prints. In particular, the green color that
> I used for a long time combines two colors that are very far apart in
> terms of UV transmission density at a given density: i.e. the yellow
> and cyan inks. When I constructed profiles using only ink combinations
> that are close in terms of UV transmission density, I got some of the
> smoothest highlight transitions ever.
>
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