The Canon Speedlite 600EX-RT Flash is a versatile, compact lighting unit that can be mounted onto the hot shoe of your Canon camera or fired wirelessly from either your camera's built-in flash optically or via radio with an ST-E3-RT transmitter. It is also compatible with Pocket Wizards. This flash improves on Canon's previous flash, the 580EX II, by adding radio transmission to the once infrared/optical-only triggering system. Radio transmission allows for easy master-slave communication between other 600 EX-RTs or with the ST-E3-RT transmitter, even when the masters and slaves are not in line-of-sight of each other. This, along with increased range, control over a larger number of flash groups, and a wider and longer zoom, makes this flash the perfect choice for wedding photographers working alone or with assistants. It is also ideal for portrait and travel photographers who need to create the biggest light possible from a very small unit.
This flash is powered by 4 AA batteries, which are not included. For extended use, attachment of the Canon CP-E4 battery pack is recommended (not included). You may also attach this flash to a Quantum battery pack with the help of the CZ cable. Note that you must still install 4 AA batteries into the flash even when using an external battery pack. This flash is durable with an easy-to-read LCD and is dust/water resistant.