Artist Bill Sullivan has taken a unique series of photos of people passing through the turnstiles of the New York city subway. The series includes 48 different shots that are haunting and fascinating at the same time. Bill describes his thought process-
I developed a situation so that various subjects could be defined by the constraints of exactly the same mechanical apparatus. The scenario consisted of someone passing through a subway turnstile. At the moment that the subjects passed through the turnstile, unknown to them, I took their picture stationed at a distance of eleven feet. I stood there turning pages of a magazine observing subjects out of the corner of my eye, waiting for only the moment when they pushed the turnstile bar to release the shutter.