[ubuntu] Cannot control screen brightness through GUI tools

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http://ubuntuforums.org – I have a Samsung Series 5 NP530U3C laptop with an Intel HD 4000 graphics card. I've found that I can't control the screen brightness with either the GUI tools (e.g. KDE's Power Management or the equivalent in Unity) or the function keys on the keyboard. However I can control the brightness by writing directly to the files in /sys/class/backlight/acpi_video0. For example Code: echo 50 > /sys/class/backlight/acpi_video0/brightness sets the screen to approx 50% brightness. Is there anything I can tweak to get the KDE and Unity power management software to be able to control the brigh (Hardware)