I agree that conversion to the ICC darkens the image and blocks up the shadows, although the effect is image dependent and more noticeable in dark-toned, low-key images. But likewise I find that a straight K7 print in GG2.2 is often weak in the shadows, again with the effect being image dependent and more noticeable in dark-toned, low-key images. Jon Cone would describe this as "open shadows", but I think there's a difference between weak images and images with open shadows and smooth tonal transitions.
I've handled this in the past using a hybrid approach. I will often create two versions - one in GG2.2 where I turn on the soft proof and darken the shadows to taste, and another where I convert to the ICC, turn on the soft proof and lighten the shadows to taste. Sometimes I have to print both to deicide which works best.
I've got a standard photoshop curve that I use to lighten the shadows. I'd like a more scientific approach. That curve in the second plot image may give me a way to create one. Moreover, using a PS curve derived this way would enable me to choose any point between the Roy Harrington approach and the John Cone approach - by varying the opacity of that curves layer.
But I'm interested in other approaches. I don't know what you mean by "map the .quad values to a 'modified gamma' curve". Perhaps it's the same thing that I'm trying to do, but expressed differently. You think so?
But one thing that I don't intend doing is building my own K7 curves from scratch using the QTR curve creation tools. I think that risks losing too much of the benefits of K7 - the smooth tonal transitions.
Incidentally, I made a comment on your bwmastery blog about comparing ABW & QTR that is awaiting moderation.
Brian
---In QuadtoneRIP@yahoogroups.com, <richard@...> wrote :
Like I said earlier in the thread, I have been kept awake with this problem off and on for the last few months/years and it all started clicking earlier last week. partly due to the conversation about the problems with QTRs linear "curve" and the reason for needing ICC profiles to match the print space to the working space. I still think using the ICC profile with QTR severely blocks up the shadows, so I was attempting to map the .quad values to a "modified gamma" curve and print without color management—kinda going in-between where there is an increased smooth transition to the dark shadows but not the hard dip that results in using the ICC profiles. The natural next step is to be able to map any existing .quad profile to different targets—either a straight linear line or "modified gamma". There is some problem if the original profile is "too far off" but what I have been testing is a way to get away from the QTR linearize function, and only use QTR to build the raw profile using the ink limits and gray overlaps. I just did a three print test series with K6 inks and that approach worked better than the standard QTR profile creation workflow of linearizing a raw curve with the 21 step target and then creating an ICC profile (or printing with just the straight line increase).
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Richard Boutwell