A quick funny story...
I was photographing a very old theater in Pasadena CA and doing the long exposure/make the people disappear thing. I was using the big Wisner 8x10.
When I developed the film, I noticed a head. One guy, curious about the camera and what I was doing, was hiding behind a pillar "spying" on me. You can see his face sharp and clear but his eyes are weird because of the blinks. It actually enhanced the shot.