moire pattern in black screens

[Breaker]

Hi all,

This is more of curiosity than a problem...

I've noticed on my D9200 + AVGA (new version) when the screen is predominantly black I see a swirl pattern (mostly along the sides of the monitor) which can best be described as a 'moire pattern'. I've tried degaussing the monitor but the pattern remains. The pattern is not present when the screen is any other color. I observed this same effect in another D9200 monitor I've seen so it may be inherant in the unit...but I thought I'd ask.

Thanks.