Here's what Halsman wrote about the picture:

"When Marilyn Monroe jumped in my studio, she bent her knees and, like a little girl, threw her legs backward. The legs disappeared and, in the moment of the picture, I saw a truncated torso. without realizing the excellence of this image, I complained that I could not see her legs.
"Marilyn," I said, "try to express your character a little more."
"You mean that my jump shows my character?" she saked hesitantly.
"Of course," I answered. "Please try it once more."
But Mrailyn stood there, pale, as though paralyzed, unable to jump. After a painful pause which seemed like an eternity, I spoke up: "All right, Marilyn, let us do some other pictures."