🚀 go-pugleaf

In article <943@elrond.CalComp.COM>, amamaral@elrond.CalComp.COM (Alan Amaral) writes:
> It's trivial.

Oh come on.  Everyone who reads this newsgroup knows how to translate between
the RGB and CMY color spaces.  And I'm sure everyone could figure out how to
do the crude undercolor removal...

The question Ed asks is not the simple one that you think he is asking.  From
his posting it is obvious that he knows about how real inks used by printers
work, and that they do not absorb light like ideal cyan, magenta, and yellow
inks.  None of the simple solutions I've posted to the net are adequate.

I have a Pantone color simulator in front of me.  Just looking at the front
page, I can see that there is no way you can print a bright orange color on
paper without using ink that is actually bright orange.

I asked this same question about a year ago.  One useful piece of information
I received was from someone at the University of Utah.  He told me that
Maureen Stone at Xerox PARC has done work in this area.  I found out she
has published papers and she recently gave a talk out here.

Ed, one thing you may want to do is buy a Pantone color simulator.  You can
get a feel for what the different inks look like when mixed together.  The
book consists of about 500 of the Pantone process colors, and then a color
chip next to them showing a close approximation using CMYK ink.  There are
three more CMYK color chips which can be torn out next to the big chip.  You
can find this at most any art store.  The price is a bit steep, $200.  The
other four Pantone books which make up the rest of the set are only $250 total.
Of course the colors printed are dependent on the ink, paper, screen angles,
etc, but you can get an idea of how things work from this book.

I know that Eikonix has a lot of people who are experts in this area, but
they're not going to divulge a lot of the information because it is
proprietary.  My personal opinion is that if Eikonix ever gets around to
announcing a Sun-3 prepress machine (if they haven't already), one of their
big features will be their expertise in color fidelity.  Our systems are
targeted at design, not production, so our "big features" are our tools for
graphic designers.

I made an error in a previous posting about halftone dot sizes.  Although
prepress machines store their pixels as 8-bit quantities, typically dot
size is controllable on an output scanner only to 2% increments, so there
are only 50 different dot sizes.  The top of the line Hell scanner generates
dots electronically at a maximum of 146 dots/mm.  If you are doing 12 halftone
dots/mm, that gives you about a 12x12 grid of dots to simulate your halftone
dot, so I guess you could assume 144 dot sizes.


Jonathan Hue	DuPont Design Technologies/Via Visuals		leadsv!eps2!jon