So far, I've run into this problem with Deus Ex and the first Thief game. With Deus Ex, changing the rendering method to OpenGL helped, but I can't do anything with Thief.
The built-in gamma controls don't do anything, and brightness on the monitor can only be ramped up so far. What causes such behaviour and how to circumvent it? My graphics card is GTX 760, and my system is Windows 8, if that's important.
Best Answer
If you are playing Thief, Thief 2, or System Shock 2 on any remotely modern system, you should be using NewDark, which fixes a lot of bugs and updates it to use modern rendering code. Scroll down to get the latest version. "Officially" it's for Thief 2 and System Shock 2, but the installation instructions also have instructions for loading Thief 1 in it.
Note that this patch obsoletes earlier patches like DDFix or the Widescreen Patch, so if you've installed those, uninstall and do a clean install of Thief to start from.