"If I drilled still another hole in the board, it would let still another image through. So I could keep drilling holes, and every time I drilled a hole I'd let an image through. In fact, I could drill so many holes that I'd drill the whole board away, and then I'd have that.
"That's what I used to think of as uninteresting diffuse white light. But there's a tremendous amount of information in the light that's incident on that board.
"One of the nice by-products of this is that, as I back up, the images overlap and you begin to get some nice patterns. Some of the images are dimmer than others. That just means that hole is smaller for some reason. Sometimes you'll see a really bright one, and that means the hole is bigger.