How to decrease brightness even more in Ubuntu?

I have been using an app called DimScreen on Windows, but I can't find any app that would make it possible for my Ubuntu. I tried xbacklight and it does not seem to work.

Do you guys know how to decrease it lower than the minimum brightness?

1 Answer

dconf approach

There are many options. But I am quite satisfied with using setting brightness value in dconf – this is a Ubuntu alternative to windows registry.

1. First, you have to enable Zoom options in settings / Universal access / Zoom /
2. Then install a nice tool to manipulate dconf and run it:

sudo apt install dconf-editor dconf-editor # this can be done from your start menu too

3. Find /org/gnome/desktop/a11y/magnifier folder (either by clicking through the tree or by hitting Ctrl+f and typing "magnif".
4. Tweak brightness-red/green/blue values
5. Or launch these commands to reduce the brightness programatically:

gsettings set org.gnome.desktop.a11y.magnifier brightness-red -0.6 gsettings set org.gnome.desktop.a11y.magnifier brightness-green -0.6 gsettings set org.gnome.desktop.a11y.magnifier brightness-blue -0.6

/sys/class approach

If you are not happy with enabling Zoom, you may try to edit brightness file in a backlight folder. At my computer, I find it on /sys/class/backlight/intel_backlight/brightness

1. I check current brightness level:

$cat /sys/class/backlight/intel_backlight/brightness 400

2. I set the file to be editable:

sudo chmod o+w /sys/class/backlight/intel_backlight/brightness

3. I decrease the brightness to 100:

echo "100" > /sys/class/backlight/intel_backlight/brightness

The lowest level seems to be "1", if I try to put "0" or invalid input, write permisssion is denied.

xrandr approach

xrandr is a great tool to handle display properties. First run it without parameters to check out your monitor names. Ex: my monitor name is eDP-1

$ xrandr
Screen 0: minimum 320 x 200, current 5208 x 1080, maximum 8192 x 8192
eDP-1 connected primary 1368x768+3840+0 (normal left inverted right x axis y axis) 309mm x 173mm

Now you can put a float number to the brightness property (software only modification):

$xrandr --output eDP-1 --brightness 0.5

As of Ubuntu 18.10, it seems I could combine all three approaches independently.