Digital BW, The Print

I just got a set of UT-14 inks to use on R280 and I'm trying to understand PR's accompanying PDF. It says:

"Glossy Papers
The system prints on glossy paper with its midtone, MIS UT type glossy- compatible inks. Because the 100% black is formed with a combination of the C and M inks, Eboni (MK) must not be used. As such, a Photoshop curve, ICC, or QTR must be used to print glossy prints."

It says "or QTR", implying that ICC and PS curves are meant to use with Epson driver. How can one prevent Epson driver from using K ink by use of ICC profiles or PS curves? I cannot wrap my head around this. Many/most RGB values will be printed by Epson driver using K ink, and it would be practically impossible to work around it, as far as I can imagine. What am I missing? With QTR, of course, it is another story.

On Feb 3, 2010, at 2:32 AM, marko.mili wrote:

> Many/most RGB values will be printed by Epson driver using K ink,  
> and it would be practically impossible to work around it, as far as  
> I can imagine.

Its possible to force input RGB values that would trigger the K ink to  
a value where they will print only with other inks via a curveset or  
an ICC profile which is just a vehicle for holding such a curveset.

C. David Tobie
Global Product Technology Manager
Digital Imaging & Home Theater
CDTobie@...


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Datacolor
www.datacolor.com/Spyder3





[Non-text portions of this message have been removed]

marko.mili schreef:
> I just got a set of UT-14 inks to use on R280 and I'm trying to understand PR's accompanying PDF. It says:
> 
> "Glossy Papers
> The system prints on glossy paper with its midtone, MIS UT type glossy- compatible inks. Because the 100% black is formed with a combination of the C and M inks, Eboni (MK) must not be used. As such, a Photoshop curve, ICC, or QTR must be used to print glossy prints."
> 
> It says "or QTR", implying that ICC and PS curves are meant to use with Epson driver. How can one prevent Epson driver from using K ink by use of ICC profiles or PS curves? I cannot wrap my head around this. Many/most RGB values will be printed by Epson driver using K ink, and it would be practically impossible to work around it, as far as I can imagine. What am I missing? With QTR, of course, it is another story.
> 
> 

Mind boggling it is but Paul did that trick already a long time ago.

K black is used in the Epson driver when enough C,M,Y, reach a value 
that equal components of C,M,Y are replaced by K. That is called black 
generation. If you for example take out C in total then no K will be 
printed. For a simple 4 or 6 ink CMYK printer model and C stays below 
50% it will not trigger K use either, the other inks can then vary over 
a wider range. Black sets only in above 50% CMY. For printer models with 
more K inks, middle grey etc this will only work when C stays below 20% 
or so as the black generation is that long, 20-100%. The dificult part 
is what you have to do with RGB curves to create the conditions on the C 
ink channel. If that is done you can pack the curves in an ICC 
RGB-device profile as David already explained.

-- 
Met vriendelijke groeten,   Ernst


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