On Saturday 04 March 2006 01:52 pm, Gerhard Fuernkranz wrote: > Cory Papenfuss wrote: > > Just as an aside, I figured there was no inherent reason to limit the > > target to just an IT8, so I tried to generate one with argyll's targen > > and printtarg. Got a target and cal file, but coulnd't figure out how > > to make the equivalent of an .ITX target that lprof liked. > > Printtarg can optionally generate a template for scanin. It should be > possible to write a program which converts a scanin template to an lprof > picker template.
The LPROF picker templates are in fact very simple. I build one for a generalized HCT chart which has over 600 patches a while back in a few hours. Unfortunately the HCT reference file is not a standard CGATS file and I need to write routines to convert this as well as the generalized HCT picker template since the actual valid patches on the HCT target varies and must be changed for each reference file in order to allow LPROF to use HCT charts. In any case as Gerhard points out it should not be too difficult to automate this. > > > It's got potential to make LOTS of color points for monitor calibration. > > For a LCD, yes, you'll likely need rather many samples. But many CRT > monitors can be characterized reasonably accurate with a simple > Matrix/GGO model - and such a model has only 5x3 degrees of freedom (if > the "upper right end" of the TRC is constrained to [1,1]), so five > independent samples should be basically enough in order that the problem > is not underdetermined and the model parameters can be solved. Of course > that's an absolute minimum, and more samples are better in order to > average out measurement errors, spatial variations, etc. > > (Btw, depending on the chosen number of orders used for modeling the > TRC, Argyll's shaper model may have some more degrees of freedom than > GGO, but it is still a rather reasonably low number) > > Regards, > Gerhard As Gerhard points out you don't need a lot of patches to get a good monitor profile. Part of this is that CRTs are in most cases "well behaved" with transfer function curves that are very close to corresponding gamma curves. If anything the IT8.7 chart is over kill for this purpose at least with CRTs. Hal ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ Lcms-user mailing list Lcms-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lcms-user
