Tuesday, April 7, 2009
Fill-In Flash
Although making dark places brighter is the primary use of flash, the next-best place to use it, surprisingly, is outdoors in bright sunlight. One of the problems of taking pictures—especially individual or group portraits—using midday sun is that the harsh lighting creates deep, distracting shadows. In people pictures, this usually means dark eye sockets and unattractive shadows under the nose and lips. Fill-in flash lightens these shadows to create more attractive portraits.
Fill-in flash looks most natural when it's about a stop darker than the main light. When the flash-to-daylight ratio is too even, or when flash overpowers the existing light, the balance looks false and draws attention to the fact that you used flash. Until the advent of built-in and dedicated accessory flash, calculating for fill-in flash was like doing the math for sending a rocket into another galaxy. It was easier (and quicker) to wait for a hazy day.
Today, most built-in and dedicated flash units have a special mode just for fill-in flash. Basically, all you do is point and shoot. The camera reads the ambient lighting and then kicks out just enough flash to fill shadows but leaves the picture natural-looking. Many dedicated accessory flash units even let you set a specific flash-to-daylight ratio, so you can make the fill more or less bright. Because a dedicated flash's output is mated to the autofocusing system, the camera even knows how far away your subject is.
Fill-in flash shouldn't be limited to taking pictures of people. I frequently use it to open up the deep shadows in close-ups of flowers or architectural details.
Using Your Light Meter
If built-in exposure meters are as sophisticated as camera manufacturers claim, why do people still get poorly exposed pictures? The truth is that while most built-in meters are fabulously accurate, they can be fooled. Fortunately, there are ways to wrestle difficult subjects into submission, provided you can recognize a difficult situation.
Light meters are calibrated to give you good exposure for subjects of average brightness; fortunately, most outdoor subjects are of average brightness. Problems pop up when you want to photograph subjects that are much lighter or darker than average. Rather than recording such scenes as you see them, the camera will see—and record—them as a medium tone. Instead of pristine white snow, you'll get a drab gray winter wonderland; instead of an inky-black horse, you'll get a gray nag.
If your subject is nearby, or very large, the simplest solution is to take a close-up reading and then adjust the exposure using your exposure-compensation dial (or manually) by a stop or two. To photograph this swan, for example, the photographer took a direct reading of the swan and then added 1 1/2 stops of exposure. This recorded the swan as white and still cast the water into blackness. To photograph a black bull in a meadow, take a reading from the animal and subtract one to two exposure stops to keep it black.
The problem gets tedious when you are photographing a relatively small average-toned subject against a very dark or light background—a friend lying on a bright sandy beach, for instance. The best recourse here is to use your spot-metering mode and take a reading of just the subject. This way, your main subject will be correctly exposed, even if, because of the contrast, you lose some detail in the background. Yet another solution is to scout the scene for something of average brightness—green foliage is good—and set your exposure for that.