[Storabrun]

Well that's a periscope view captured by a camera after it went though the lens in the camera. It's not the same as what you see when you put your own eye to that periscope. The most realistic view we can get in a game like this is to have as little black as possible showing. The observation scope in OLC GUI is the best example I have seen so far. Your screen is already taking up a very small part of your field of vision, there is absolutely no reason (if realism is the concern) to lessen that field even further by adding large black areas around it.

Edit: Maybe I didn't make myself clear enough. My point was that the most realistic scope view is when it fills your whole screen, no black at all or maybe just a tiny bit in the corners. You can't use a brush in a picture editor to achieve that.