My screen keeps changing brightness!

My 21.5 imac keeps changing screen brightness, it goes from 100% brightness to 80 or 60% brightness every few seconds and then back to 100%. what is going on? how can i fix this? its really bugging me.

I don't know if the iMac has the same ambient light auto adjust as the MBPs do but if it does then that's likely the causes of your problem. To fix it go into system preferences and in the display icon uncheck the automatically adjust brightness as ambient light changes.

i called the mac people they have no idea what to do either.. im starting to hate macs/apple -.-

Hey, now you’re sounding like a troll, IMO.

Try a permissions repair.

Auto brightness is in Settings

Take a look at the attached image, turn off this feature in your Settings to disable your MacBook from taking control of the light! Just don't go into the darkness.;P