Not just anyone could become John Lennon and Yoko Ono’s personal photographer—but then, Bob Gruen wasn’t just any photographer. The New Yorker had a knack for capturing even rock’s surliest frontmen, focusing his lens on everyone from the former Beatle to the Sex Pistols to Led Zeppelin. This is the guy who Alice Cooper dubbed “the ultimate backstage pass,” and it all becomes very clear why while watching Don Letts’ documentary on Gruen, Rock’n’Roll Exposed. With a free screening on Sunday as part of BAMcinemaFest, there’s no excuse to not see it. Before you do, blast Double Fantasy and pull on one of these rock star-inspired pieces.