Installed Ubuntu a few days ago, right from the installation the screen is really, I mean, really dim.
My graphics is Nvidia go 7900 GS. Ubuntu recognizes the card and assigns it a NOUVEAU driver, there are other 3 XORG Nvidia current drivers available as well. I tried them and YES it did get rid of the dimness, but other issues arose.
Somehow it affected my USB speakers and the sound is all crackly and when I switch back to NOUVEAU the sound is much better, and also when shutting down there is no Ubuntu logo, only ugly pixelated screen showing me how its killing all the processes, the same on start up.
But when Using Noveau everything works as should but the screen is awfully dark, and yes I did play with brightness settings, it's maxed out.