Originally from an older post but I dug it up just for you:
1> start ps and go to a dark place (sewers or death realm are ideal).
2> open system preferences from the apple menu.
3> select displays.
4> click the colour tab.
on the left hand side you should now see at least one pre configured profile - simply click calibrate. This helps you set up a new profile which will appear next to your original profile in the future.
5> on the first screen of the calibration wizard make sure you check the \"expert mode\" box, as this gives you extra options which may prove useful later.
6> follow the instructions on the 2nd, 3rd, 4th 5th and 6th screens.
7> now we come to the gamma settings screen. drag the slider all the way over to the left and click continue.
8> on the next screen do not alter the white point, simply click continue.
9> leave \"allow other users to use this calibration\" checked. click continue.
10> choose a name for your new profile - i called mine PsDarkPlaces. click continue.
11> click done.
now whenever you are in a dark place and need extra light to find your way around simply open system preferences from the apple menu, go to displays, click the colour tab and select the profile PsDarkPlaces (or whatever you called it).
Voila - extra brightness.
Just a word of warning though - remember to switch your profile back to the original configuration when you close planeshift, you will probably find this new profile too bright / harsh on the eyes for everyday computing - similarly you may wish to switch back when you are in well lit areas of the game - the easiest way to do this is to leave system prefs open on the displays screen while you are playing, then you can switch to it from the dock when you need to change profiles.
If you happen to create a profile which you no longer need you can delete it by navigating to :
MacintoshHD>library>coloursync>profiles>displays
....the profiles you create (and the default one - dont delete that!) reside here, so theyre simple enough to get rid of.
Hope this has been helpful