8.1 TYPES OF FLASH

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Flash photography has come a long way since the 19th century when a photographer had to ignite a tray filled with gunpowder to illuminate a scene. Almost every digital camera comes with a small built-in automatic flash that is tied into the autoexposure system. These flash units are convenient, however their range is very short; normally around 10 feet or so. They are also so close to the lens, photos of people often capture them with red eyes. They emit a hard, direct light and can’t be rotated to bounce flash off a wall or ceiling to soften it.

Flash on camera is convenient to use: every place you and your camera go, the flash goes with you. All flash-on-camera photos look very much the same—a flat, relatively shadowless light that minimizes surface textures and volumes.

To overcome these limitations, a variety of external flash units are made. These units work like those on 35mm SLR’s. They either slip into a "hot shoe" on the digital camera that both holds them and connects them to the camera shutter release and autoexposure system, or they are mounted on brackets and connected to the camera by a synch cord, basically a small cable. This synch (pronounced "sink") cord makes the same electrical connection that the hot shoe does but lets you position the flash off camera.

Another way to use external flash is to buy a slave flash unit that fires automatically when it senses the burst of flash from the camera’s built-in flash unit. Since many digital cameras fire the flash twice for each picture (the first is a preflash to set color balance), these units have to be adjustable so they fire when the camera’s second flash goes off. These units are more powerful than the on-camera flash and also allow you to rotate the head to use bounce flash to soften shadows.

A slave flash unit. Courtesy of Digi-Slave.