Ever-popular Norman Rockwell painted in a realist style, but a close examination of the 40 original Rockwell paintings and studies and of all 323 of his vintage Saturday Evening Post covers in this touring exhibition suggests he was more of a fabulist than a realist. He painted archetypes, not people, idealized visions rather than depictions of how things really were. Among the exceptions: the civil rights-themed studies for “The Problem We All Live With” which capture a significant moment in American history, giving them a lasting documentary value.