Sorry to be the Noob here (as I'm relatively new to Minecraft!), but does this stop mobs spawning near by, or is it purely to help you see whilst mining etc?
Thanks for your answer I just thought I'd ask before I went around as if nothing could hurt me haha! Thanks!
Just did this recently, turned my gamma up to 8000. xD It actually works fine in bright places too, and when I place a torch in a 'dark' cave, it doesn't change the brightness at all. As in, I don't blind myself when I place a torch.
Oh wait it works again... that was weird, the ''Gamma'' option disappeared from my options folder and then came back after some time.