Harry Benson has photographed pop stars and presidents, supermodels and Jimmy Stewart. He was behind the lens during the civil rights marches, during Martin Luther King’s funeral, and when Bobby Kennedy was assassinated. On Sept. 11, hearing of the attacks on the World Trade Center, Benson grabbed his camera and headed to downtown Manhattan. Says the 71-year-old Scot, simply, ”It’s what I do.”

You can sense that disarming directness in every Benson shot: There’s no pretense, no posturing, just a fecund hiccup of hang time while stardom or history passes in front of his camera. ”I like to keep people moving,” admits the photographer in his easygoing burr. ”I don’t want them just standing there posing with great light. Then what you’ve got is a great picture of f — -all. Just a self-serving picture.”

Right there’s the echo of the hard-nosed kid from Glasgow who dropped out of school at 13 and who learned the photojournalist’s trade in the cutthroat world of London’s Fleet Street. Still, Benson, who for 37 years has been a New York-based contributor to major news and fashion magazines, puts his greatest faith in serendipity. And why not? It was a random assignment to cover the Beatles during their 1964 U.S. visit that made his career. ”I didn’t really want to do it,” he laughs. ”I wanted to go to Africa — I was a serious journalist! We had no idea what was going to happen. But I think I got them at the right time, just before the peak.”

His new book, Harry Benson: Fifty Years in Pictures (Harry N. Abrams), reprints dozens of personal pinnacles, images that testify to Benson’s knack for grabbing the odd, telling moment. ”I’m not looking for what’s going right in a shoot,” he says, inadvertently summing up his philosophy. ”I’m looking for what’s going wrong. Then it becomes interesting.” The following portfolio shows what happens when Benson is in the right place at the wrong time.