Screen brightness problem while watching video

[cnone]

Hello, I have been using sparky - mate for 3 months. But I have a problem with watching videos.
Lets say I start playing video on VLC or Youtube, my screen gets brighter and brighter that I cant even see white objects in the video and when I close the video  I can observe the same problem on my applications too(Forexample Iceweasel is turns to super white).
But When I quit from full screen mode, everything turns normal again in a few second.
Have any of you experienced a problem like that?
Thanks.