Re: Digital Tones Needed for Pt/Pd Prints

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From: Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Date: 05/03/00-09:55:58 AM Z


Darryl Baird wrote:
> ...
> > How can the yellow ink be kept at a fixed level at larger values of
> > black ink?
>
> You're seeing the effect of pre-press technology know as either UCR
> (under color removal) or GCR (gray color removal) which indeed reduce
> the amounts of colors, other than black, when black is present.
> The printing press can produce a fine black with less additional colors,
> so it uses these schemes to effectively reduce the total amount of ink,
> to speed drying, and reduce waste. I believe you can either turn these
> off or at least modify them to respond in the way you desire...that's
> the part I'd have to look up and test

I have selected GCR with maximum black, otherwise the black will have
color componants. This has been part of the only way I have been able
to elliminate the cyan and magenta inks from being printed when black is
called for. There is no control to only add a yellow componant as all
(CYM) are adjusted together by the separation options.

Katharine Thayer wrote:
> ...
> Under Color Settings<Separation Options you have the option, not of
> turning them off but at least of switching from GCR (the default) to
> UCR. This might appear on the face of it to solve your problem because
> UCR substitutes black for colors only in neutral areas where there is
> equal amounts of yellow cyan and magenta in your file.

No, GCR with maximum black selected is what I want for printing the
black.

> ...these separation options only work for PostScript printers; your inkjet
> printer driver will ignore them. I don't know of any way to set CMYK
> values that won't be overridden by your printer driver other than by
> installing a RIP.

I do not know for sure if the printer driver is ignoring them, but it
does seem to respond to the separation options and not override the
colors as selected in Photoshop as I am only getting black and yellow
ink printed for the most part (viewed with a magnifier). However, I
must play a trick on Photoshop to get the colors right. The scan is
RGB, converted to 16-bit (otherwise information is lost and values
merged), then converted to grayscale (removes color information), then
converted to RGB (without the trip to grayscale and back cyan and
magenta are not removed from the image even after the levels to yellow
and black are set [I have tried many adjustmens, color corection, etc
and this trip has been the only thing to work.]), then converted to
8-bit, two layers (yellow and black) are made with levels and curves
adjusted, the levels are multiplied, then flattened, a final curve
adjustment (taking care to adjust RGB componants so that no value is out
of gamut). The printer has color management turned off, but all devices
and Photoshop are set to sRGB.

I have not found a RIP for the HP DeskJet 970Cse. Please let me know if
you know of one. I have tried to get by without and seemingly am doing
so (but would prefer a RIP). The major issue remains the total number
of tones that can be generated.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/


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