I'm not familiar with specifying the gamut mapping. Are you saying I should specify that the profile is to be used only with, say, images that are in the sRGB space?
Yes. By default, profile will generate a profile with just a colorimetric table, giving absolute or relative colorimetric intent. Only if a source gamut (usually defined by a profile) is supplied can perceptual or saturation intent tables be generated (You can't really do gamut mapping if the source gamut is unknown). To avoid gamut clipping, perceptual or saturation intent needs to be used. For the best result (ie, say printing), then I really recommend "smart" or "active" linking be used (icclink -G), resulting in a device link profile. This allows more flexibility in choosing intent, and a far smoother transform than using the B2A table in a profile, even if it is configured for the source profile in question.
I've never had to do this with Monaco OptixPro software, and it doesn't produce the posterization so I was surprised to see posterization in Argyll. I tried creating the profile again with -qh and it improved somewhat; I'm tempted to try -qu now ;-)
Sorry, it's hard to draw conclusions without any details. Other profilers fudge perceptual gamut mapping, often using a generalized gamut mapping. Sometimes they give you some controls to tweak it. This may well be smoother than gamut clipping, but will be far from optimal for a given transform.
profile -v -A "Lenovo" -M "T60" -D "T60 IPS" T42pk1f500What intent tables were built.Don't know - can you tell by the commad line?
Yes, you only built colorimetric intent. See <http://www.argyllcms.com/doc/profile.html#s> and the discussion in <http://www.argyllcms.com/doc/Scenarios.html#PP5>.
Don't know - must you specifiy this? I thought that was an optimization only, that you could still get a good profile without limiting it to one source profile?
It depends on what you mean by "good profile". To some people, a good profile is one that represents the behaviour of the device well, ie. how good it's colorimetric A2B table is, since this is what captures the essential character of the device, and with a "smart" linker is what counts when using it for output, or for recreating B2A tables. If you intent to use it in conventional "dumb" linking scenarios, then the characteristics of the various intent B2A tables (which are the ICC way of trading speed for accuracy) will be of interest to you.
Well you should (I hope!) get a better result if there was a perceptual table in the profile, especially if it was created for an sRGB source gamut.
Using MS or Adobe color engine - are they passive? I don't know for sure what the difference is.
In general it's passive ("dumb"), the only exception being the BPC feature, which actively alters the gamut mapping in the luminance axis. You shouldn't need/use BPC for an Argyll profile perceptual intent that has been created for the particular source profile you are using though. So try again using something like: profile -v -A "Lenovo" -M "T60" -D "T60 IPS" -S srgb.icm T42pk1f500 and see if it is different, and possibly looks somewhat better. Graeme Gill.