Halo Effect

Rittenhouse Park is all lit up with gold lights. I walked through one night and paused at the giant tree in the center of the park. A distance away, two men stood in the shadows talking and gesturing to each other. One of them stood in front of a lamp so that most of his head was blocking the lamplight from reaching me-- except for a thin ring of light outlining the shape of his head like a halo. I'd seen this before in photos of people. It didn't necessarily have to be completely dark, either, to create this divine effect. I made a mental note to use this Halo Effect in a future photo.

Update:

Thanks, Andrew, for the spectacular example!