Problem with disc or what?

[AutomaticDriver]

I just finished watching A Nightmare on Elm Street(2010). Throughout the whole movie the black bars(top and bottom) would either flash lighter or brighter(whatever you want to call it).

Is that a disc problem or is that normal?

I have never noticed it before. Maybe it happens on other movies but I never noticed it because this movie is so dark that I able to notice things like that?

If this is the wrong forum. Please move it. Thank you.