Determining Your Digital Photography Lighting Needs

Your digital dream camera's electronic flash capabilities (or lack of them) should be on your list of things to evaluate before you make a purchase decision. Not every photo is possible using existing light. Even if you have plenty of light, you might still want to fill in those inky shadows with an electronic flash. Your camera's built-in flash features are definitely something to consider.

Most digital cameras have a built-in flash unit that can be turned on, flipped up, swung out, or otherwise activated when you want to use a flash — or when the camera decides for you that the flash is required. (Usually, a tip-off is a flashing red light in your viewfinder or next to it. Time to flip up that flash!)

You should be aware that most flash units are good only over a particular range. If you've ever seen a fan stand up in the balcony at a Bruce Springsteen concert and take a flash picture of the Boss from 100 feet away, you'll understand just how limited flash is at long distances. Some units are so feeble that they can only illuminate subjects 2 to 12 feet away. Others have special settings to spread the flash illumination for wide-angle shots or tighten it up for telephoto pictures.

Here are some features to look for in an electronic flash:

• Auto-on: It's useful to have a flash that can be set to flash only when it's needed. Some cameras require you to flip up the flash to use it. Others build the flash into the body of the camera in such a way that the flash can be used anytime.

• Autoexposure: An electronic flash can sense the amount of light reflected from the subject and turn itself off when the exposure is sufficient.

• Red-eye prevention: Some flashes can be set to produce a short preflash just before the picture is taken. That causes the subjects' irises to contract, reducing the possibility of the dreaded red-eye effect. Alternatively, the preflash can fool your subjects into thinking that their ordeal is over and produce some priceless weird expressions.

• External flash capabilities: At times, you want to use an external flash, either in concert with or instead of your camera's built-in flash. See whether your camera has either a built-in flash-sync socket or a hot shoe that you can use to mount an external flash and connect the camera to the flash. Keep in mind that many digital cameras require you to use only a particular brand of flash to retain the automated exposure features or (in some cases) to avoid frying your camera's flash-triggering circuit with too much voltage. If you're thinking of using a slave sensor to trigger the flash, make sure that it can be used with your camera. The preflash of some cameras will set off the slave unit. Figure 1 shows an external flash unit fitted with a diffusing dome to soften the illumination.