QTR-Quadtone RIP

Richard,

Yes, I mean Roy Harrington and I am familiar with the Piezography method to print the GO in a separate pass. That was why I mentioned it as a possible reason for reserving the 255 value. Jon Cone seems to work closely with Roy.

The reason I got into this was because I was trying to find a simple way to teach students to calibrate digital negatives without the need for a densitometer. The Chartthrob automated plug-in in Photoshop seemed like a good alternative but, the way it works as originally written, you have to apply the adjustment curve in Photoshop to a positive image then invert the image to a negative before printing. I wanted to apply the adjustment curve in QTR. I spoke with the Charttrob developer and he provided a version that has an option to create a negative curve which can be used in QTR to print a positive image and wind up with a negative. The only problem was the 255 issue.  Roy explained the reasoning to me and the fix is to have no value higher than 254 in your positive.

I prefer to embed the correction curve in QTR rather than applying it to the image in Photoshop. I have no proof other than an intuition (and a hope) that doing it that way is less destructive to the image. Ron Reeder has suggested that it is better and it just seems like it should be better to control the ink distribution (which would be linear) rather than create gaps in your histogram.

I’m glad this subject has suddenly raised so much discussion after many months. I too hope Roy will provide a version of QTR that doesn’t reserve the 255 value. 

Alan

> On Jan 7, 2015, at 7:29 PM, richard@richardboutwell.com [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
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> In normal usage you want to keep 255 as pure white. I just tested a few ways of editing an ink descriptor file to cause an ink to fire at 255, but when looking at that channel in the .quad files its clear that anything in 255 gets converted to 0. 
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> Alan, do you mean Roy Harrington? When you print with a gloss optimizer with piezography you are printing a white patch with a separate profile thats only value is the ink limit set to the 255 value. When I print digital negatives with the piezography system i don't even worry about the GO—Just pass and that is it.  (although i did use it for printing on gold leaf backed transparencies using the full k7 inks)
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> If you do want an ink to fire at 255 you would need to go into the .quad file and change the first value below "# INK Curve" from 0 to what ever value you wanted between 0-65535 (that upper limit of 65535 is 100% of that channel firing. It is like printing the 100% patch of that ink's separation image calibration mode with the ink limit set to 100).
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> In any case, I wouldn't worry about it. If you are making digital negatives just invert in photoshop and send that to the printer and don'tworry about trying to embed an inverting curve into the QTR profile. 
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> Richard Boutwell
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