Artist Ed Ruscha's career-spanning retrospective

The largest exhibition ever of works by Ed Ruscha, one of the most celebrated American artists of the postwar era, is now on display at the Museum of Modern Art in New York City. Ruscha, now 85, talks with correspondent David Pogue about collecting much of his life’s work into one retrospective; the cryptic nature of many of his paintings; and his use of unusual materials (like chocolate and axle grease).