[argyllcms] Re: ColorMunki measurement drift
- From: Roger Breton <graxx@xxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 25 Sep 2010 23:01:34 -0400
Hallo Juergen,
I am impressed by your determination. I wish you had an EyeOnePro to
compare, 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).
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.
MfG / Roger
> -----Original Message-----
> From: argyllcms-bounce@xxxxxxxxxxxxx [mailto:argyllcms-
> bounce@xxxxxxxxxxxxx] On Behalf Of Juergen Lilien
> Sent: 25 septembre 2010 22:06
> To: argyllcms@xxxxxxxxxxxxx
> Subject: [argyllcms] ColorMunki measurement drift
>
> Hello everyone,
>
> I am still researching why it is very difficult to get repeatable
> (stable) measurements with my ColorMunki, and why the measured white
> point seems often to be off several hundred Kelvin, compared to my
> manufacturer pre-calibrated monitor (NEC PA series).
>
> In a first try I attached the ColorMunki to the screen and let it take
more than
> 1200 white point measurements (hires adaptive mode) in a row, this took
> roughly an hour. At this time the monitor was several hours in on state,
so it
> should be pretty stable.
>
> Please have a look at the attached graphs (each measurement is a point),
the
> complete "-d6" logfile is available on request.
>
> The measured luminance was, after a very short stable beginning,
constantly
> decreasing (from about 133 to 130 cd/m²) with no stable endpoint in sight.
>
> The color (X/Y) measurements are even more interesting, they are also
> decreasing but the variance is not constant, there are knots in the point
> graphs with less variance and the period between the knots is increasing
> over time - the pattern is more stretched.
> At the end the measurements seem to have reached a semi constant state
> with nearly no further decreasing tendency.
>
> My first thought was to wait an hour with the ColorMunki on the screen,
until
> the color measurements reach the stable bottom, before starting
calibration
> and profiling. The problem is, that the first (highest) readings seem a
lot
> more reasonable compared to my pre-calibrated monitor presets, and even
> after a self- calibration of the ColorMunki they never get back to the
start
> level. Yes, this effect (temperature drift?) seems to be at least partly
> immune against self-calibration of the instrument!
>
> To prove this I started a second series of measurements with a self-
> calibration after each single measurement and I still see decreasing
> luminance and X/Y color values.
>
> To be honest, I'm lost at the moment...
>
> What is your ColorMunki operating experience?
> Is my ColorMunki broken?
>
> Should I reinstall the X-Rite software and check if I see the same
decreasing
> measurement values?
>
> And what is the practical relevance? The DE of the first measurement was
2,6
> and it dropped to 0,7 at the end, a 1,9 DE white point difference should
be
> visible(?).
>
> As I understand the new -I option will only help to counteract drifting in
the
> brightness level measurements, but does not help with the color/white
point
> drift?
>
> You see, any input is greatly appreciated! ;-)
>
> Best regards, Juergen
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