something is wrong with my screen calibration


I have rather a strange problem: I have a wide gamut screen BenQ SW240. I am hardware-calibrating it with the BenQ software Palette Master Element on Windows 10. After that, I profile it with Displaycal on Debian Bullseye. I have this screen since a little more than 6 months now, so far I did not have any problems with it.
However, today, after hardware calibration where I set white level to 120 cd, I set Displaycal to 120 cd as well so the interactive tool measures the brightness, just to check. Actually I almost always do/did this. But today Displaycal said twice that brightness was only 100 cd. So I performed hardware calibration again. But the result is the same. So what is going on here? Why is my screen darker on Linux than on Windows?
Well, I don’t think there is a link to the fact that I have a new laptop with dual graphics (Nvidia+Intel), is there? On Linux, I use Bumblebee. Anyway, this was the first time that I calibrated my screen with my new laptop.

Thanks in advance and regards


Just a long shot I am not super well versed in color calibration. The DisplayCAL developer helped ensure I did my iMac properly.

Could it be possible that Linux is automatically dimming your display brightness through power management?

It is not power management. Power management cannot set the brightness of external screens. And meanwhile I checked on Windows too: Displaycal measures less brightness there too. I am not sure, I will check the colorimeter corrections that I installed in Displaycal/Argyll. Anyway one of the programs, either BenQ PME or Displaycal/Argyll measures brightness incorrectly. Maybe it is a bug but in which program?
Btw: I am using a Spyder5
But, well, first I have to warm up my screen…

I happened to be reading the DisplayCAL documentation last night and I noticed in the White level section that it says, “Note that many of the instruments are not particularly accurate when assessing the absolute display brightness in cd/m2.”

I was actually scouring some threads in my search about the Spectral: Corrections for my iMac the other day and I just recalled a few instances saying that the Spyder devices themselves have some issues managing absolute brights and darks. Not saying this is the issue. Just a lot of information out there seems to hate on Spyder checkers. I had a Spyder5 but the device failed after like 2 months and started giving really bad red tints no matter what I did so I replaced it with a ColorMunki Display.

I would ere on the side that DisplayCAL is more correct in its readings than other software mostly just because that is what all my research pointed to. If the particular display however has internal hardware LUTs I don’t know if DisplayCAL can do those so you would need the vendor specific software for that.

Either way I am not sure why you would get drastically different readings like that with different software that is a rather large margin of error that I have never come across before. So software bug or some other issue hardware/correction issue might for sure be the cause.

Hi, thanks for the answers. Looks like the latest version of Palette Master Element is broken. I installed an older version, now I am getting the right brightess but still struggling with color temperature. So far it only calibrated to 6600 k instead of 6000.

Anyway it is possible that the Spyder is broken but so far it works well with Displaycal.

How about using your camera to test/proof your monitor/Spyder settings?

Have fun!
Claes in Lund, Schweden

Thanks. Did not know about that, will check it out.
But the problem seems to be solved. Latest PME is broken (apparently closed source software is buggy too - what a surprize). Calibration is perfect now.

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