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I've got two displays. One is approximately six years old: Fujitsu P24-5 ECO (LCD/IPS, CCFL backlight), the other one is a DELL U2412M (LCD/IPS, LED backlight).

I've tried to color calibrate both displays (LinuxMint, dispcalGUI, 6500K, 140cdm²) with three different colorimeters that I could access (an old-ish Pantone Huey Pro, a brand-new Colormunki Smile and my very own brand-new Colormunki Display).

With all three colorimeters (and a handfull of different settings concerning the profile type etc, including color correction matrices for the Dell Display with the Colormunki Display - couldn't find correction matrices for the Fujitsu) the results were essentially the same: Checking with the eye the white point seemed to be very close for both displays, as were brightness etc. But on closer Inspection the Fujitsu does have a slight red-ish tint (compared to the DELL, that doesn't yet imply which one is closer to the "real" colour). This is almost not noticable (i. e. only with side-by-side comparison) for sunsets or brown leafs, but it's a big difference for lighter skin tones (giving someone a sunburn only on the Fujitsu Display).

On yet closer inspection the TRC curves of the display profiles (that I can view from the colour panel in my system settings) look a bit different:

Dell TRC curve

The Dell TRC curve has all three colors of RGB neatly on top of each other.

Fujitsu TRC curve

The Fujitsu TRC curve seems to indicate that red is somehow intensified.

That said, I don't know the real meaning of this curve. Especially I don't under stand why, if its meaning should be "right, the Fujitsu is tinted red" why this wasn't compensated through the display. Or could it be the other way round: Red is intensified by the profile because the instrument read a smaller brightness for red and wants to compensate for that.

But then, if the latter should be the case: I did calibrate the displays with the colorimeters before each profiling, so the colors brightnesses at maximum brightness should have been essentially the same to begin with - at least that was the colorimeter readout during calibration.

Could it be, that the instruments read the three colors differently during calibration vs. profiling?

I really don't understand what's happening here. My expectation would have been two essentially equal color reproductions on both displays.

Would it help to buy a spectrometer (e.g. Colormunki Photo)? Or what else could I do?

EDIT: MirekE suggested in an answer to try and set the standard observer on dispcal (-Q 1964_10). Unfortunately this doesn't change much and the problem still exists.

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In DispCalcGui go to Options->Set additional command line arguments... New dialog box should open with a list of tools. In the box that says "dispcal" enter -Q 1964_10 and see if it makes any difference. This parameter sets standard observer to CIE 1964 10º, which reportedly improves the results when matching multiple displays with different backlighting technology.

  • Thanks for the answer. I'll try that out and come back with the results. – jnfingerle Apr 10 '15 at 8:02
  • Ok. I've tried it out, but the outcome is essentially the same. Even though this answer didn't help me, I sincerely hope, that it will help someday someone else in a similar situation (hence the upvote), but for my situation I still need another solution. – jnfingerle Apr 11 '15 at 14:39
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To answer my own question: As it turns out, the effect I was seeing was created by some weird color management behaviour in darktable. Even though darktable-cmstest reported for both screens that "the X atom and colord returned the same profile", the weird behaviour went away with a configuration setting: I've now set the GUI option how darktable locates the color profile from all to Colord, and everything works fine, so far. :-)

I achieved this thanks to help on the dispcalgui-users ML. (Follow the link for the thread there.

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I'v get a Spyder4Elite where you can choose an option to match multiple screens called "StudioMatch". Don't you have the same with the ColorMunki software? I suppose it's named differently.

  • I'm on Linux (so the vendor software won't run) with dispcalGUI. I'm unaware of any such option in dispcalGUI nor the underlying command line programs. :-( – jnfingerle Apr 13 '15 at 12:31
  • Unfortunately not. Give it a try calibrating to the identical settings for all of them. – Ruben Carmona Apr 21 '15 at 7:45
  • Well, yes, for all I know, that's what I did. – jnfingerle Apr 21 '15 at 7:57

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