I have installed Ubuntu 13.04 and the proprietary AMD catalyst driver 13.4.
After installing the driver, the brightness of the screen has turned to the lowest and can not be changed. No matter how I scrolled the brightness bar, the brightness doesn't change.
I tried editing grub with
acpi_backlight=vendor. But, it didn't work and the brightness hotkeys stopped working.
Note that Ubuntu 12.04 works perfectly without a single issue. What can I do to solve the problem in Ubuntu 13.04?