FPS drops with ligting effects

[rastamun1234]

so im usually around 300-400 fps then sometimes when something with lighting effects appears on my screen it will drop to like 10-20. Any ideas on how to combat this?

[Game]

Interesting, do you run windowed mode or full screen? Also, how often is this?

[emre2010]

same here mostly 600-700 fps and suddenly i get 3 fps 4 fps or 10 fps in windowed mode