I've heard a story about a photograph that was taken of an "empty" Grand Central Station by a photographer who used a several hour long exposure. Because no one stood in a single spot for any significant fraction of the exposure the room looks empty even though there was traffic passing through all day. I consider myself a pretty good search-engine monkey, but aside from some anecdotes I havent been able to find this photo, its title, or it's author. I'm posting here in hopes that somoene will know what I'm talking about and give me some information. Thanks.