Cameras have undoubtedly increased in sophistication over the last ten years or so, with features such as auto-focus and built-in flashguns now being commonplace. On the other hand, a few "standard" features seem to have become rarities, and the humble flash socket certainly falls into this category.

For most users this lack of an external flash connector is probably of little consequence, but it is a major drawback for anyone wishing to go beyond simple "point and shoot" flash photography. One solution is to use a second flashgun, well separated from the main flashgun, to provide some fill-in lighting.

If a camera lacks a flash socket but does have a built-in flashgun, it is actually possible to use a second gun. In order to fire the secondary guns it is merely necessary to have each one triggered via a slave unit. A flash slave is just a high-speed light activated switch that triggers a secondary flashgun when it detects the flash of light from the main gun.

Provided the camera has a built-in flash unit, flash slaves enable any number of extra flashguns to be used without the need for any form of external flash connections on the camera. This low-cost starter project describes how to construct such a flash slave.