single photos Now you see them - now you don't

I often do this for any night shots involving people (or architecture). The first photo is wide open f2.8 for around 20 seconds. This eliminated all of the people that were moving (almost there are still a couple of ghosts). The area was wall to wall people and the sidewalk was not visible at all. The second photo I stopped down to f16 or f22 which made for an exposure of a couple of minutes. Now everyone that wasn't sitting down or standing at a tripod disappeared. Honest, when I took the lower photo the sidewalk was jammed with people.