LG 27UL550-W ddcutil notes
Backlight control
$ ddcutil setvcp 10 $percentage
where 10 = VCP code for backlight
Picture mode
Propritrary extension.VCP code: 0x15. Changing 0x15 alone is not sufficient maybe, picture modes change backlight sometimes too.
Reader mode:
$ ddcutil setvcp 15 1 --force
$ ddcutil setvcp 10 23
Reversing settings for other modes
$ # Dump current settings
$ ddcutil getvcp scan -v > 1
$ # Change monitor settings using the buttons
$ ddcutil getvcp scan -v > 2
$ diff 1 2