Lenovo Y500 can't set brightness

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http://askubuntu.com – I've installed Ubuntu on a Lenovo Y500 laptop (2012), video card is Nvidia 650M (no integrated graphics), I'm using driver 310.19. The problem is that I can't adjust brightness at all. If I press the relevant media keys, the indicator in ubuntu works correctly but the brightness is not changed. So far I've tried the following: Editing xorg.conf in this way: Section "Device" Identifier "Device0" Driver "nvidia" VendorName "NVIDIA Corporation" Option "RegistryDwords" "EnableBrightnessControl=1" EndSection Adding the options acpi_osi=linux acpi_backlig (HowTos)