If you've read How Cameras Work, you know that it takes a lot of light to expose a vivid image onto film. For most indoor photography, where there is relatively little ambient light, you either need to expose the film for a longer period of time or momentarily increase the light level to get a clear picture. Increasing the exposure time doesn't work well for most subjects, because any quick motion, including the movement of the camera itself, makes for a blurry picture.
Electronic flashes are a simple, cheap solution to this inherent problem in photography. Their sole purpose is to emit a short burst of bright light when you release the shutter. This illuminates the room for the fraction of a second the film is exposed.
In this article, we'll find out exactly how these devices carry out this important task. As we'll see, a standard camera flash is a great demonstration of how basic electronic components can work together in a simple circuit.