# Screen backlight correction on iMac / Linux

Before, I have changed backlight with:

``` bash
xrandr --output eDP --brightness 0.8
```

But after switching to Debian / i3, found that  screen brightness correction works not like before - even the picture less bright, it looks like back or foreground LED ones still turned on max.

After some time of researching, found new option for my hardware configuration (it was 255 by default):

``` bash
echo 50 > /sys/class/backlight/radeon_bl1/brightness
```

Now picture looks more contrast and colorful, before apply the recipe above, I had changed acpi_backlight to native in

``` /etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi_backlight=native"
```

then

``` bash
update-grub
```

Some other tips:

=> https://wiki.archlinux.org/title/Backlight