From The Joys of Jumpology, by Roberta Smith of The New York Times:

When the photographer Philippe Halsman said, “Jump,” no one asked how high. People simply pushed off or leapt up to the extent that physical ability and personal decorum allowed. In that airborne instant Mr. Halsman clicked the shutter. He called his method jumpology. When you ask someone to jump, Halsman said, “the mask falls, so that the real person appears.” The idea of having people jump for the camera can seem like a gimmick, but it is telling that jumpology shares a few syllables with psychology. As Halsman, who died in 1979, said, “When you ask a person to jump, his attention is mostly directed toward the act of jumping, and the mask falls, so that the real person appears.”

One of the purest examples of this joy is the image of Halsman himself, holding hands with a smiling Marilyn Monroe several feet off the ground. Facing his partner, he seems ecstatic, as if he cannot believe his luck. He will hang with one of the world’s most photogenic beauties for eternity. The two are caught in nearly matching, tucked-knees positions.