XRandR – How to Change LCD Brightness

brightnessxrandr

How to change brightness of LCD want image look deemed and soft the

xrandr --output LVDS1 --gamma 0.8:0.8:1.1

change only gamma but not the brightness of image. I have no option –brightness for xrandr

Best Answer

From man xrandr (this is not listed in the -h options, but it works for me):

--brightness brightness

Multiply the gamma values on the crtc currently attached to the output to specified floating value. Useful for overly bright or overly dim outputs. However, this is a software only modification, if your hardware has support to actually change the brightness, you will probably prefer to use xbacklight.

I don't know if there is a universal standard for manipulating LCD brightness; if not this will become a matter of hardware drivers, etc.

Which I suspect it is; trying xbacklight -get on my philips LED gave:

»xbacklight -get
No outputs have backlight property

Guess I am stuck using the gimpy buttons on the panel. ;)

BTW: xrandr --brightness does exactly the same thing as using three identical values with --gamma.

Those who want to change their gamma/brightness:

Use xrandr to list your outputs:

$ xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
DVI-0 connected 1024x768+0+0 (normal left inverted right x axis y axis) 304mm x 228mm

As you can see my output is DVI-0 to change the brightness:

xrandr --output DVI-0 --brightness 2

To change the gamma:

xrandr --output DVI-0 --gamma 2:2:1

How to make xrandr modifications persist for more than 1 second

What you want, is to set the backlight to your desired value. Since you are on Gnome 3, you might want to change it in Gnome.

gdbus call --session --dest org.gnome.SettingsDaemon.Power --object-path /org/gnome/SettingsDaemon/Power --method org.freedesktop.DBus.Properties.Set org.gnome.SettingsDaemon.Power.Screen Brightness "50"

If that does not work, the ArchWiki has many alternatives, including ACPI and kernel parameters ...

Select your monitors in the following:

# ls /sys/class/backlight/

inspect the maximum brightness:

# cat /sys/class/backlight/<device>/max_brightness

Then you set it to your desired value:

# echo 5 > /sys/class/backlight/acpi_video0/brightness

Source (ArchWiki): https://wiki.archlinux.org/index.php/backlight

DISCLAIMER: I do not run Gnome 3, so cannot test this.

Best Answer

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How to change the Xorg gamma/brightness

Those who want to change their gamma/brightness:

How to make xrandr modifications persist for more than 1 second

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