It's a credit to Side by Side—an impressively thorough, expertly assembled survey of the debate surrounding the movie industry's transition from celluloid to digital filmmaking—that even disinterested viewers will have complicated feelings about the aesthetic, practical, and philosophical questions director Chris Kenneally poses. It's not as heavy as all that—producer Keanu Reeves plays interlocutor with a number of filmmakers, including Martin Scorsese, Steven Soderbergh, George Lucas, and Lena Dunham, adding a certain chumminess, and the history of the digital-image revolution is laid out in illuminating rather than stultifying terms. Reeves' contraction-free, schoolboy narration suits some overly basic explications ("One of the first steps of the production process," we are informed, "is capturing the image in camera"), but there's too much substance here (plus the reliably tart presence of David Fincher) for Side by Side to get all tied up in its couple of kinks. If loyalties are staked out, few are ironclad; cinematographers, camera makers, and color correctors chime in about shifting film-crew dynamics. At its most fascinating, Side by Side examines the idea that changing formats means changing not just the way movies are made but also watched, adjusting the essence of what looks and feels "real."