For his first English-language film, Michelangelo Antonioni set a metaphysical mystery in the world of fashion, at a time when the director’s metaphysics had itself become a fad; the movie and its meaning were the talk of the swingingest parties of 1966. Photographer David Hemmings snaps images of Vanessa Redgrave and an older man apparently trysting in a London park; later, analyzing the eyelines, scrutinizing the grain, he believes he sees evidence of murder, but finds that the harder you look, the less you know. The same interpretive limits apply to the viewing of Blow-Up: Is this portrayal of youth culture, with its pot parties and Yardbirds shows, its rehearsed rebellion and limitless cool, affectionate—perhaps parodic—or is it a lament over the inscrutable emptiness of hip? Is it really about philosophical depths, or fascinating surfaces? Like its closing game of mime-tennis, the film may be daring us to focus on something that doesn’t exist. Keep your eye on the ball.