Throughout his long and successful career (five decades and counting), Bob Dylan has been a chameleon, switching personas and musical styles the way other performers change costumes. He confounded fans by transforming from acoustic folkie to electrified rocker to country singer, and that was just in the 1960s alone. Director-cowriter Todd Haynes (Far from Heaven) tries to pin down who Dylan really is in the fascinating I'm Not There by having six actors portray the musician's different life stages. His Dylans include a black child (Marcus Carl Franklin), Blanchett in drag (her jivey, jittery Dylan is the high point of the film), Bale, Ledger, Gere and Ben Whishaw. But in the end, the troubadour remains as unknowable as ever, which just may be the point.