2

I increase and reduce the LCD brightness on the command line as described here1:
xrandr --output HDMI-0 --brightness 0.2

My problem is that my brightness setting is automatically reset after a few seconds.

My workaround is a small Autokey (Python) script (gist) that permanently sets my setting.
How can it be done better without this little unnecessary extra CPU load?

Operating System: Kubuntu 20.04

KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.4.0-52-generic
OS Type: 64-bit

1: By the way: There is a question with the same name, but it describes a slightly different problem. Is there a way to permanently set the brightness level

SL5net
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  • `xrandr` won't work with Wayland (let alone it doesn't work with some graphics drivers), thus is not the ideal way for a modern Kubuntu system (it has been *sunsetted* by KDE). Sorry I use Lubuntu so can provide the lxqt commands but not appropriate KDE commands. – guiverc Nov 06 '20 at 06:52

2 Answers2

1

That must be due to Redshift/Night Color. Use the command sudo apt remove redshift to uninstall redshift. In case Night Color is enabled, disable it in system settings.

If you are using a laptop, you can control brightness with the function keys, there's no need to use xrandr.

If you are using a desktop, you can use Brightness Controller, which is a GUI tool to control brightness, and it can also change the color temperature (it uses xrandr in the backend)

sudo add-apt-repository ppa:apandada1/brightness-controller
sudo apt update
sudo apt install brightness-controller

image

(disclaimer - I am one of the developers of this software)

You will have to disable Night Color to use Brightness Controller (note that it does not work with Wayland).

Archisman Panigrahi
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  • Since the problem is no longer there, at the moment, at almost 8 a.m., I suspect that you are right. I'll test this out tonight. – SL5net Nov 06 '20 at 06:57
  • Yes, I had "Night Color" activated so that I (my eyes) get tired in the evening and I don't work too long. It is described in the "Night Color" GUI as: "makes the colors on the screen warmer to reduce eye strain" ([imgur](https://i.imgur.com/AKdLdg2.png)). – SL5net Nov 06 '20 at 07:09
  • @SL5net Check my edited answer. You can disable night color and use an alternative software which can control both brightness and color of the screen – Archisman Panigrahi Nov 06 '20 at 07:54
  • Found this is a long-known open issue with redshift [open since 2015](https://github.com/jonls/redshift/issues/175). Workarounds for this already exist, but you have to make the settings yourself during the day. they does not change automatically (depending on time / latitude/longitude ) – SL5net Nov 06 '20 at 08:24
0

This is a long-known open (Nov2020) bug with redshift (bug open since 2015). Described here githubredshift issues 175 and something similar here how-to-use-xrandr-gamma-for-gnome-night-light-like-usage.

Some Workarounds (not yet completely substitute solutions):

most of they does not change automatically depending on day time and recommends detestation of redshift

SL5net
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