Gamma settings?

In dark areas, things seem to go pitch black and around them are yellow/red spots. I’m sure it has to do with the gamma settings, but there aren’t any in gmod for me to change. In other source games there are, and I don’t have any problems in them with dark areas. Help? :frown:

http://img262.imageshack.us/img262/4489/rpdowntownv20001.jpg

:saddowns: