A dedicated flash is an external flash unit that is made for a specific camera system, such as Canon’s EX range of
Speedlites for use with EOS and selected
PowerShot models. A dedicated flash communicates electronically with the camera, allowing it to sync with the camera’s
aperture,
shutter speed and
exposure settings. On the other hand, a non-dedicated flash is made by a different company, and typically will not communicate with the camera to the extent that it can be used automatically. This is why you should always use Canon Speedlites with your
Canon camera.