Report Gamma or Brightness settings have no effect on brightness on Debian Sid with an Sapphire RX 480 in TDM Tech Support Posted March 30, 2017 A bit late to the party, but this issue was due to using Xorg modesetting(video driver?). I also played Soma about 1-2 months ago and it had the same issue, couldn't change gamma/brightness settings. After asking on forums, I was linked to https://bugs.freedesktop.org/show_bug.cgi?id=27222, where one of the devs says: https://bugs.freedesktop.org/show_bug.cgi?id=27222#c26 (In reply to Luke from comment #25)> Seems to be broken again on xorg-server-1.19.1. It was working find on> Fedora 25 with my Intel HD 5500 (Broadwell GT2) . After I upgraded from> 1.19.0 to 1.19.1, the gamma controls stopped working and everything is dark> again.Make sure you're not using the modesetting driver, that one doesn't support gamma control yet.