The brightness icon is shown but nothing happens. Even if I try to change the brightness in "System Settings" nothing happens. The thing is it didn't happen with Ubuntu 13.04, so I would like to know how to solve it or how to erase the upgrade to use the 13.04 version.
Got the workaround for this
Edit the file
/etc/default/grub. Change the line:
GRUB_CMDLINE_LINUX="quiet splash acpi_osi=Linux acpi_backlight=vendor"
and then save and then run:
Then restart the computer, then it should work.
This might allow you to reduce the brightness from 'Brightness & Lock' in system settings. But your function combination keys might not work. Though this is not a perfect solution, you can get the job done with this :-)
One thing to try would be to create the file /usr/share/X11/xorg.conf.d/20-intel.conf with the following content:
Identifier "card0" Driver "intel" Option "Backlight" "intel_backlight" BusID "PCI:0:2:0"
...and log out and back in again to see if it works. Try it without any additional kernel parameters.