MacBook Pro Display too dark for movies.

How do I adjust the MacBook Pro display/screen to view movies/TV properly? I view Netflix, I might play a DVD, or use iTunes. The screen brightness does not accommodate darker scenes. It was working for a while; the contrast(?) changed when the onscreen toolbar appeared and disappeared. Then, the darker scenes appeared viewable.

Apparently, I stumbled on the adjustment at some point, because the screen adjusted, but I don't remember what I did (boo-hoo).

Your help is greatly appreciated.