The German artist Gerhard Richter creates explosive psychedelic canvases in dense improvised layers. He's like a slow-motion action painter, using a giant homemade squeegee to cover what he's just painted (with the base colors peering through), and Corinna Belz's documentary records his method with a kind of solemn excitement. It helps that Richter, filmed here in his late 70s, doesn't take his art so seriously that he ever forgets it's really a form of play. The film is sketchy as biography, but it proves an aging artist can still crackle with the electricity of youth. A-

