1. You want to print the test picture without changing it, that is, without changing the underlying luminosity numbers. AdobeRBG also has a gamma of 2.2 and so for these purposes can be regarded as the RGB equivalent of Grey Gamma 2.2. If you look at the histogram when you convert from GG22 to AdobeRGB you'll see that the histogram doesn't change, just that you now have three channels rather than one. You need to do this in order to assign the picture to sRGB, because you can't assign a greyscale image direct to an RGB ICC profile, and you certainly don't want to convert it to sRGB - that's what you're trying to avoid Photoshop doing to it behind the scenes. Thus you need a two-step procedure.
2. In short, yes. You don't need to worry about the AdobeRGB conversion because you're intending to change the test ramp rather than trying to leave it unchanged. There is one qualification to this which I have failed to mention, and that is that the ICC that you create using the QTR tools will need to be an RGB profile. That is, you will need to use QTR-Create-ICC-RGB.exe rather than QTR-Create-ICC.exe. With an RGB profile you can then assign to sRGB, something that you couldn't do with one of QTR's greyscale ICCs.
Of course this convoluted workflow is only required to print to ABW on Windows using an ICC. The workflow for printing via QTRGui has none of this complexity. Well, almost none. Because QTRGui is not a colour-managed application, if you want to use an ICC to print, you'll need to convert the image to an ICC in Photoshop and save a copy for printing. This workflow is simpler on a Mac, because Print Took will allow you to print to either QTR or ABW using an ICC on-the-fly. Of course this raises the hotly-contested question about whether you *should* use an ICC for printing via QTR, but that's a separate question.
---In QuadtoneRIP@yahoogroups.com, <per@...> wrote :
Thanks for your detailed answer Brian. I am finally getting around to testing this flow. Here are two questions:
1. When I print my test picture to measure, why is it necessary to convert to adobeRGB from the assigned gray 2.2? I understand that you have to force photoshop to think the picture is already in sRGB, but what does the conversion from gray 2.2 to adobeRGB do?
2. Assume I followed the flow to print a test ramp without ICC and created an ICC profile from the result. If I now wanted to check that the same ramp now is linear after correction, would I 1) load the untagged ramp, 2) assigning it gray gamma 2.2, 3) converting it to my ICC profile, 3) assigning it srgb, 4) print? Or does there have to be a conversion to adobeRGB too in there somewhere?
Kind regards,
-Per