CPN Explains Canon's Wireless Flash Systems

From the Canon Professional Network:

Canon’s wireless flash system means that you can fire two or more Speedlites together without any cables linking them.

Working with multiple Speedlites gives you creative control over your subject lighting. A main light can be used away from the camera, and other units can be used to provide backlighting or illuminate the background.

It has been possible to work with two or more flash units almost since the day they were invented. However, the problem has always been getting the exposure correct. Just synchronizing the flash outputs is not enough. You also need to control each output to give the correct amount of light for the subject.

Canon’s wireless flash does away with all this. You just set up the Speedlites and press the camera’s shutter release button. A series of pre-flashes are fired and the system automatically calculates the output required from each unit. It then fires all the units to give what should be a correctly exposed, well-balanced flash image.

The Canon wireless flash system is based on a master-slave relationship. The master unit is a flashgun, flash transmitter or built-in flash master fitted on or connected to the camera. The slave units are positioned on their own away from the camera. You can work with one master and one slave unit, or one master and between three and five slave groups. Each slave group can have one or more units. The system is very versatile, allowing almost unlimited control and creativity.

There are two types of wireless flash control within the Canon system. The newest and most versatile is the Radio Wireless system, introduced with the Speedlite 600EX-RT. The original system is an optical pulsed light system, found on previous Speedlite models.

Want even more details about Canon Speedlites? Check out Bryan's Speedlite flash reviews.