Every line in a picture elicits an emotional response. A horizontal line generates calm, whereas a vertical feels stable and dignified. But a diagonal is nonstop action-a line on the move. And it can breathe life into an otherwise static composition.

Any line can be turned into a diagonal if you shoot at an angle. Even more impressive, and often more interesting, are the many natural diagonals to be found-if you just take a look.

For example, at a bird market in Singapore, I saw this cage partly covered by a well-weathered and fortuitously ripped newspaper. With my camera and 80-200mm lens on a tripod, I set the focal length to 180mm. I had my assistant hold up a piece of colored fabric about three feet behind the cage to separate the birds from the ugly concrete wall in the background.

This difference in contrast between the colored background and the birds in their cage emphasized the converging diagonals and their message of activity.

Like that newspaper, which begs to be pulled away to reveal the rest of the birdcage, the outer leaves on this ear of corn cry out to be pulled down.

The crisscrossing diagonal lines of the leaves create an active counterpoint to the horizontal dimples in the corn kernels and the vertical lines in the brown silk.

Keeping the diagonal tire tracks on this snowy intersection just outside the corners of the image’s frame strengthens their graphic impact.