No documentary is objective. Even when a nonfiction film lacks narration, a storyline, or Michael Moore, someone has to decide what to leave in and what to leave out. That’s what any kind of art is: deciding what to leave in and what to leave out. The particular art of the fly-on-the-wall documentary has been practiced and perfected for a half-century now by Frederick Wiseman, the wizened octogenarian who won an honorary Oscar last year (a very hip choice on the Academy’s part). In an age when documentaries continue to push for telling stories—easily digested, preferably with a theme of redemption, and accompanied by an insistent musical score, because the goal is to uplift and energize you—Wiseman stubbornly disdains all that. His new film, Ex Libris: New York Public Library, is like an old card catalog organized according to the Dewey Decimal System: calm, useful, elegant.