[argyllcms] Re: How do I force dispcal to always map R0 B0 G0 -> R0 B0 G0 on the calibrated video LUT?

  • From: Alexander <adfirestone@xxxxxxxxx>
  • To: argyllcms <argyllcms@xxxxxxxxxxxxx>
  • Date: Fri, 25 Dec 2009 23:55:05 -0800

> Why don't you try the adaptive mode and see what you
>> think:
>>        spotread -e
>> vs. display mode:
>>        spotread -d
> spotread -e appears to fluctuate less than half as much as spotread -d over
> multiple readings, which is excellent. I'm definitely looking forward to
> trying out dispcal -V when RC3 is released.
> The measurements between the two modes differ a bit though. Should I be
> assuming that the spotread -e measurements are more correct than the
> spotread -d measurements?
> Below are multiple measurements of the same gray patch on my CRT (set to
> 2048x1536 @85Hz / ~85cd/m2 white / ~0.01cd/m2 black) with an uncalibrated
> video lut:
> http://pastebin.com/f7ed5671f

Graeme, do you have any insight about this?

Does the difference I'm seeing between the spotread -e and spotread -d modes
appear normal to you? For reference, I did use -N when switching between -e
and -d in order to eliminate the internal sensor calibration as an
additional variable.

The resulting color temperatures between the two modes seem close enough,
but the color coordinates and resulting Delta E values differ somewhat

They can't both be correct, so which should I trust as being more accurate?

Another thing that I found a bit curious was how much my measurements of a
completely black screen varied every time I did an internal calibration of
the sensor. Below are only -e results, but the -d measurements were also
showing similar changes between internal sensor calibrations when measuring
my near 0.00cd/m2 black-point.

The first internal sensor calibration gave me color temperature results like
the following:
CCT = 2500K
Closest Planckian temperature = 2500K
Closest Daylight temperature  = 2500K

The second internal sensor calibration gave:
CCT = 2500K
Closest Planckian temperature = 999999K
Closest Daylight temperature  = 34999K

The third internal sensor calibration gave:
CCT = 9000K
Closest Planckian temperature = 7000K
Closest Daylight temperature  = 7000K

See full results here: http://pastebin.com/f3cec1649

I don't expect the Eye-One Pro to be all that accurate so close to 0.00
cd/m2, but the above seems a bit odd. The first result seems sensible with
CCT, Planckian, and Daylight all having similar temperatures. On the second
the CCT stayed similar to the first, but the Planckian and Daylight
temperatures were being reported as out-of-range values. The third which was
taken about an hour later then the first also seems sensible, but it is
significantly different then the others. What do you think?

Other related posts: