Brightness automatically diming


macrumors member
Original poster
Jan 2, 2007
Hi everyone,

I have an Intel iMac, and for some reason every once in a while after I boot my machine the screen's brightness is very low, much lower than what I usually keep it at.

When this happens, I simply open the display preferences and increase the brightness to the appropriate level, but it is a little annoying. Most of the time my screen remembers it's brightness settings when I turn it on and off.

Does anyone know why this is happening? Is there anyway to "fix" this?


macrumors Core
Mar 17, 2005
London, England
Could it be the ambient light sensor?

go into system prefs > displays > uncheck "automatically adjust brightness as ambient light changes"