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

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 22 Dec 2009 10:42:28 +1100

Alexander wrote:

So for example, if I set the minimum accurate measurement range to 0.15
cd/m2, once Argyll reads a patch with a luminance of 0.15 cd/m2, it then
records it as the lowest valid reading. It would skip all patch measurments
between 0.00-0.15 cd/m2 and in just evenly space any remaining luminance
measurements below 0.15cd/m2 (since Argyll appears to calculate the native
gamma of the the display, it should be able to make a reasonably accurate
guess of where those low luminance values would likely fall on the gamma
curve) while using the same R:B:G ratio that was found when measured at
0.15cd/m2.

Heuristics are often fragile, and it would make for a great deal of
complexity to provide some sort of estimate of the minimum reliable
reading of each type of instrument in each type of mode, particularly
if the mode is dynamic (true of many of the colorimeters that
are based on Light to Frequency sensors). There's no real telling
what a display does as it goes to black either - my CRT has quite large
"dead" zones, and interpolating the readings would give a poor
correlation to its actual behavior (it doesn't go below 0.1 though).

Why don't you try the adaptive mode and see what you
think:

        spotread -e

vs. display mode:

        spotread -d

Now before getting too far astray, can you say a little more about how that
-V parameter will work?

Will the -V parameter have a number value after it? If not, then I assume it
just tells Argyll to disable heuristics?

It just tells Argyll to use the emissive mode of the instrument rather than
display mode. For the i1pro emissive mode uses adaptive integration and gain.
For most other types of instruments there is no difference between these modes.

Graeme Gill.

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