I found this question, and that works on my VGA monitor, but my main monitor is connected via HDMI, and xcalib and xgamma don't work on it. How do I reduce the gamma? This is really getting to be an issue because I can hardly use this OS because of how bright the white is.

3 Answers 3


I had this exact problem and was about to post a question on it, but managed to find an answer.

First use:


To find the name of the output. It could be (HDMI-0 or HDMI-1 etc.)

Then do:

xrandr --output <Channel> --brightness <Level>

Brightness is a decimal number from 0 to 1. For example, this is the command I did to fix my problem:

xrandr --output HDMI-0 --brightness 0.8

xrandr --output {Channel} --gamma R:G:B

for example:

xrandr --output HDMI1 --gamma .5:.5:.5


I just installed QRedshift to solve the same problem. It lets you adjust brightness, color temp, and gamma for daytime vs nighttime use with your mouse. I bumped my gamma up from 1.0 to 1.1 and it's made a noticeable difference.

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