Please try the kernel at the link below. I think this should get you a samsung backlight and eliminate the acpi_video one. After booting to this kernel please verify that samsung-laptop is loaded, that you have /sys/class/backlight/samsung and no longer have /sys/class/backlight/acpi_video*, and that the Fn keys work for adjusting the backlight level.
Please try the kernel at the link below. I think this should get you a samsung backlight and eliminate the acpi_video one. After booting to this kernel please verify that samsung-laptop is loaded, that you have /sys/class/ backlight/ samsung and no longer have /sys/class/ backlight/ acpi_video* , and that the Fn keys work for adjusting the backlight level.
http:// people. canonical. com/~sforshee/ lp1086921/ linux-3. 7.0-5.13~ lp1086921v20121 2052012/