GammaAdjuster is a good program to adjust gamma level, if your screen is too bright or too dark, you can now simply change it by this tool.
It's very usefull when you're playing serious sam on high brightness, and it crashes (then screen stays bright if on OpenGL), this tool will bring normal brightness again.
Just unpack rar file, and place GammaAdjuster.exe wherever you want to.
If your SS crash, only thing you need to do is move the gamma level slider, and then set it again to 1. More simple is to set hotkey. For example: set Num+ for increase gamma level, and Num- for decreasing it. When sam crash, the only thing you need to do is just press those keys in any order!!!!! .