There was a famous photographer named Philippe Halsman who had over 100 covers of Life Magazine to his credit. He was also famous for his collection of photographs in which he asked his subjects to "jump" for the photo. He loved stopping the motion with his camera and also felt that when he asked a subject to jump you got to see the real person because he or she was more interested in the act of jumping than in being self-conscious in front of the camera.
Just by accident a few years ago I copied Halsman's idea when I started asking little children to dance or jump near the end of the session. Kids seem to think that this is such a unique idea that they really relax and have a little fun.
I've had a couple of good "jumpers" lately. My littlest jumper is Sara Grace Hodges who was just in yesterday. Every mother prays for their two-year old to be as perfect as she was -- just an angel to work with and her jumping left her pigtails flying. My older jumper is high school senior Greyson Harrell who brought great enthusiasm and height to her jumps. At her age I suspect she's "jumping for joy" at being a senior.