Hallo Jurgen, I have both a ColorMunki and an EyeOnePro here. Maybe you can guide me in some comparative testing for you? I'm kind of busy these days but I can give it a try... BTW, I am no video engineer but, sometimes, I wonder to what extent is the 110V/220V input voltage fluctuation could influence the monitor emitted light? Crazy idea, I know. First reading, you say, was "White level = 156.70 cd/m^2" + "6610K". After 19 consecutive readings, you say you get "White level = 152.46 cd/m^2" + "6958K". The Luminance drop is only 3%, which is not so bad. But I agree the CCT shift of +348K is troubling? Black level going up, anything below 1 cd/m2 measured with these "affordable" instruments (i1pro, Munki, DTP92), is to be taken with a grain of salt, IMO. These instruments are never sensitive enough to measure such low light levels with any precision or accuracy. I would like to try to replicate your findings, if I could? You may have a slightly "defective" ColorMunki, unless they all measure with that kind of precision. Which I'm not sure. MfG / Roger > -----Original Message----- > From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms- > bounce@xxxxxxxxxxxxx] On Behalf Of Juergen Lilien > Sent: 26 septembre 2010 11:19 > To: argyllcms@xxxxxxxxxxxxx > Subject: [argyllcms] Re: ColorMunki measurement drift > > Roger Breton wrote: > > Hello Roger! > > > I wish you had an EyeOnePro to compare, ... > > Yeah, that's my wish too. ;-) > > > ...because, to my knowledge, EyeOnePros are not susceptible to the > > effects you describe (if EyeOnePro drifted as much as you report, I > > would start to worry). > > I started with a Spyder2 years ago, but the results were not to my > satisfaction, so I thought to make a big step forward with the ColorMunki, > only to find there is still something fishy with my instrument readings. > It would be really interesting to compare with an EyeOnePro, but I've read a > recommendation to sent an EyeOnePro once a year to the manufacturer for > recalibration, so I would expect that inter instrument agreement is not > without problems, especially between different types of instruments (e.g. > EyeOnePro and ColorMunki). > > Of cause, I would by happy with my ColorMunki to get very similar results > with two measurements being 30min apart. > > > Do you leave the ColorMunki hung to the screen for an hour before > > making your measurements? To try minimizing thermochromism effects? > > It should help, in my opinion. > > Actually I found the problem during the interactive calibration of the monitor. > It is really a hunt to set the white point within > <0,2 DE. After several readings the DE starts to increase again, so I have to > push the monitor controls one more step, and so on. > I found that this iterative procedure takes more than 30min to get in the > region of more stable readings, that actually result in better looking LUT > curves. So yes, recently I leave the ColorMunki roughly an hour on the screen > (measuring the white point) before I start over with the real > calibration/profilation. > > But the problem remains, that the agreement between monitor (preset) and > ColorMunki constantly degrades after the first reading (without > acclimatization time) even with self-calibration. > > E.g. monitor preset is 6500K (Blackbody): > > First measurement of uncalibrated response with "cold" ColorMunki: > > Black level = 0.22 cd/m^2 > White level = 156.70 cd/m^2 > Aprox. gamma = 2.19 > Contrast ratio = 721:1 > White chromaticity coordinates 0.3115, 0.3242 > White Correlated Color Temperature = 6610K, DE 2K to locus = 2.1 > White Correlated Daylight Temperature = 6612K, DE 2K to locus = 2.8 > White Visual Color Temperature = 6534K, DE 2K to locus = 2.0 > White Visual Daylight Temperature = 6720K, DE 2K to locus = 2.7 > > This looks quite reasonable, but 19 consecutive measurements > _with_prior_self-calibration_ later I get this: > > Black level = 0.24 cd/m^2 > White level = 152.46 cd/m^2 > Aprox. gamma = 2.17 > Contrast ratio = 642:1 > White chromaticity coordinates 0.3064, 0.3196 > White Correlated Color Temperature = 6958K, DE 2K to locus = 2.4 > White Correlated Daylight Temperature = 6960K, DE 2K to locus = 2.4 > White Visual Color Temperature = 6854K, DE 2K to locus = 2.3 > White Visual Daylight Temperature = 7065K, DE 2K to locus = 2.3 > > Despite the self-calibration the black level is up, white level + gamma (+ > contrast ratio) are all down and the white point has changed about nearly > 350K in the wrong direction. > > What's going on here? > > Best regards, Juergen