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This question overlaps with Lenovo ThinkPad X1 Yoga OLED Brightness and Can't control the display brightness on Lenovo X1 yoga OLED, except that these questions' answers reduces the color depth because it's software solution, and not hardware like pulse width modulation used on android phones, which reduces brightness but not color depth.

How can it be done with Ubuntu/Linux?

LyingOnTheSky
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  • Have you tried using the xrandr --gamma options in conjunction with the xrandr --brightness option? – WinEunuuchs2Unix Feb 09 '18 at 11:52
  • @WinEunuuchs2Unix Yes, I don't understand the gamma, but it lowered the color depth even more. – LyingOnTheSky Feb 09 '18 at 11:56
  • If you changed gamma to 0.9:0.9:0.9 and that made it worse then maybe something like 1.1:1.1:1.1 will make it better? – WinEunuuchs2Unix Feb 09 '18 at 11:57
  • @WinEunuuchs2Unix still worse, I think that gamma changes the distribution of the light (e.g. higher gamma shaves more brightness to the top, less colors at the bottom, worse color depth) – LyingOnTheSky Feb 09 '18 at 11:59
  • @WinEunuuchs2Unix another attempt is: http://www.armadeus.org/wiki/index.php?title=PWM, I tried running modprobe imx-pwm to get pwm in /sys but I got an error that the module not found, I think that link is outdated or I am missing something. – LyingOnTheSky Feb 09 '18 at 12:01
  • I wonder if this would help?: https://askubuntu.com/questions/424732/how-do-i-calibrate-colors-without-extra-hardware-like-dccw-exe-on-windows – WinEunuuchs2Unix Feb 09 '18 at 12:02
  • @WinEunuuchs2Unix this is a software solution too. – LyingOnTheSky Feb 09 '18 at 12:08
  • Awww I see. You are looking for a hardware solution where a hardware solution isn't possible from all I've read so far? – WinEunuuchs2Unix Feb 09 '18 at 12:42
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    @WinEunuuchs2Unix yes because software can't emulate true lower brightness at all. It needs to tell the hardware to do that, one example is PWM. – LyingOnTheSky Feb 09 '18 at 13:10

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