Notice in this picture the way that the heel of the woman's right shoe meets the shadow of the toe of her left shoe, which itself barely touches the left edge of the image. It is a beautiful pictorial design, as satisfying to contemplate as it would have been difficult to predict. Recognizing and enjoying it does not keep us, the viewers, from sharing in the fun of the couple on Coronado Beach, or from wondering what became of them and their friend with the camera, who appears as a shadow in the foreground. Indeed, the special pleasure of the picture is that it gives us both things at once: the exuberant couple, who were there on the beach, and the design, which came into existence only when the photograph was made.
The picture is a snapshot, and it is unlikely that the untutored photographer who made it sought, or expected, the remarkable result or would have been able to repeat it. Nevertheless, exquisite accidents of this sort have played an important role in the evolution of the art of photography, by teaching ambitious photographers to appreciate and anticipate them.
from The Museum of Modern Art, MoMA Highlights, New York: The Museum of Modern Art, revised 2004, originally published 1999, p. 136