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+# 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