[ubuntu] iMac 12,1 (mid 2011 21.5) 13.04 Brightness.

Hello All,

I've installed Ubuntu 13.04 as a dual boot with OSX and in Ubuntu on my mid 2011 21.5 iMac I cannot change the brightness. I've Googled until my head hurts but none of the solutions work for me. Any ideas? Thanks.

Scott