Thanks for you quick response. Yes, I've been doing both a profile and calibration. The luminance I'm interested in XYZ. And when I do a calibration with a target gamma of 1.0, and then do report on calibrated monitor (using DisplayCalGUI) I get the native gamma, not 1.0. Moreover, quick spotreads verify that the gamma isn't close to 1.0. On Tue, Jul 5, 2011 at 7:33 PM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote: > Geoff Ghose wrote: > >> I apologize if this is a very basic question, but I'm really quite lost. I >> want an icc monitor >> profile that approximates linear input to luminance. (Yes, I realize that >> it can only be an >> approximation, and will suffer especially at low values). >> > > Please read > <http://www.argyllcms.com/doc/**calvschar.html<http://www.argyllcms.com/doc/calvschar.html> > >. > > Now do you mean a profile or calibration ? > > A monitor profile doesn't give you any particular luminance, it > characterizes > the device (i.e. tells you what XYZ/D50 L*a*b* value you get for any > RGB input). > > > So an RGB value of 128,128,128 is half the luminance of 255,255,255. (This >> are for visual >> psychophysics experiments). >> > > Luminance defined in what space ? L*a*b* space ? Jab space ? XYZ space ? > They will all be different. > > > I have tried setting target gamma to 1.0, but that really doesn't seem to >> do much of anything: >> when I run a report on the uncalibrated and calibrated monitors I get >> essentially the same >> gamma. My impression is that all the calibration is doing is trying to >> ensure that the color >> temperature is pretty consistent across input levels, but not remapping >> the input output >> relationship so as to significantly change gamma. >> > > Sounds like you are talking about calibration. You can setup a calibration > that maps > RGB to L* using the dispcal -gl, but note that if you are interested in > precisely > what's going on, the non-zero nature of black on a real device will mess > this > up - see > <http://www.argyllcms.com/doc/**dispcal.html#g<http://www.argyllcms.com/doc/dispcal.html#g> > > > > Graeme Gill. > >