External flash

A flashgun designed to clip to the top of the camera on its accessory shoe or to be used off-camera and fired remotely by cable, radio control or infra-red. External flashguns have more power than the camera’s built-in flash and a lot more flexibility in the way you can control and direct the light.

Commander mode (Nikon)

A flash control mode on some Nikon DSLRs and external flashguns (Speedlights) which can fire other Speedlights remotely via infra-red. It’s possible to control quite complex lighting setups in this way, and it’s part of Nikon’s CLS (Creative Lighting System).