How to Shoot a Backlit Photo

If you use your flash only when it automatically pops up on your camera, you are missing a great opportunity to improve your portraits.

The flash is the answer to a common problem that occurs when there is a strong light behind a subject, even in broad daylight. “People pose on the beaches of Cabo San Lucas and the sun is behind them and they cannot understand why they are darkly lit or silhouetted,” said Bryan Peterson, who tackles this and a variety of lighting issues in his latest book, “Exposure Solutions.”

The reason is the camera’s light meter is setting itself based on the intense sunlight in the background. That leaves even slight shadows grossly underlit, so your subject’s face is just a murky outline.

Mr. Peterson teaches his students how to solve this problem to produce “one of the most rewarding portraits you can take,” e said. “You whip out the telephoto lens, and put your subject with their head blocking the sun.” Then use the flash. The result is a photo with golden overtones and a subject framed by a shimmering nimbus of light.

Here is Mr. Peterson’s formula for the shot.

Go Manual. To get this shot consistently you must learn to use your camera’s manual settings. So first, get your camera’s instructions and find out how to turn off the automatic mode. You will also need to know where the ISO, aperture, shutter speed and flash settings are. It’s not as hard as it may sound.

Low ISO. Choosing an ISO is like picking a film speed, and as with film, the faster the speed, the more that a grainy texture called noise will show. Higher ISO can also cause problems synchronizing with some flashes. Mr. Peterson prefers a low ISO of 200. “You have greater contrast and greater sharpness because there is no noise,” Mr. Peterson said.

High Depth.! Do you want the background artfully fuzzy or sharply focused If you have a beautiful sky, you want a lot of depth of field, so close the aperture. The higher the F-number, the more closed it is, so pick F16 or F22, Mr. Peterson said.

Closed Aperture. With the aperture set, adjust the shutter speed until the meter shows you are in the correct exposure range, or minus one stop, to make the sky richer in color. Don’t aim the camera right at the sun though; take a meter reading off to the side a bit so the clouds will be exposed perfectly.

Auto Flash. The final setting is to make sure your flash is on automatic exposure mode; again check your instructions. It will make sure the subject in the foreground is properly lit. With more practice, you can get more creative using the flash set on manual, too.

Put the sun behind your subject’s head, and voilà. Not only will you have a shot worth framing, but, as Mr. Peterson has discovered from his classe, the motivation to keep learning new techniques. “The elation people feel from that one little flash tip,” he said, “keeps them gong for years.”