Charles Gatewood has spent a lifetime photographing the edges of his surroundings. Instead of Bob Dylan on stage in all his glory in the 1960s, Gatewood captured Dylan sitting down with a cigarette. Instead of Wall Street big-wigs showing off in the 1970s, Gatewood captured anonymous bankers walking along the streets to their Wall Street jobs. And so it went for the San Francisco photographer, who has spent five decades in his chosen profession. "Charles Gatewood: 50 Years" — opening Thursday, Sept. 5, at Robert Tat Gallery, with a reception and book signing on Saturday, Sept. 7 — is a retrospective of all the nooks and crannies that Gatewood has entered in his life, including the underground sex scenes that Gatewood documented with authority. In person, Gatewood is as interesting as his photographs — a dynamic that's often missing for well-known image-makers. But, then, Gatewood has always been an exception to the rule.