So if you are in a dark cave, the lighting changes drastically for different direction you face (assuming there isn't any torch or light source nearby)? If not, that's just how lighting works in this game. Drink a cat potion when you go into dark caves/places/or at night and you should see things fine.
The problem is, it also happens outside of cave with lots of light. In dialogue scene, if the camera direction changes to face the one who talks, then brightness automatically changes so one character is hard to see and other is too bright.
If this is how the lighting works in Witcher 2, then it might be graphic card setting problem?? I have two 470 gtx with SLI connection.
Its almost certainly a graphics setting problem as I have managed to get through the darkest caves without Cat, which makes everything too washed out for my taste, n I'm only running a single 460. What drivers are you using NV bought out a set of betas for witcher 2 last week. they're 275.27 for 7 n Vista I dunno if they did the same for xp or not.