Delyan, are you able to force the NVIDIA proprietary driver to control the backlight? You can do this by adding
Option "RegistryDwords" "EnableBrightnessControl=1
to the "Devices" section of xorg.conf and then restarting. Also, does your backlight emit a buzz or humming noise when the brightness has been changed using the NVIDIA drivers?
Delyan, are you able to force the NVIDIA proprietary driver to control the backlight? You can do this by adding
Option "RegistryDwords" "EnableBrightne ssControl= 1
to the "Devices" section of xorg.conf and then restarting. Also, does your backlight emit a buzz or humming noise when the brightness has been changed using the NVIDIA drivers?