It is hard to describe what Black Crush is. You have to see it by yourself.

Or you watch this video. I have shot this in one of the moments when you play a game (here: Bioshot Infinite) and you feel: something is wrong. Like there is some kind of shadow over the screen which does not belong there. Then you move the had to left or right and you realize it: the black crush has hit you gain!

I admit, it's a S-PVA monitor from the last century but still a good one (Eizo) and the VAs I have seen in the last couple of years were not much better, you just have to watch the "right" scene where the gray/brown parts are dark enough, i.e. close enough to the point when VA gamma shift goes crazy.