The Opteka EF-600 DG SUPER is designed to work with Canon Digital SLR cameras, for advanced flash photography. It has a maximum guide number of 148 feet or 45 meter at 85mm focal length (ISO 100).The zoom angle of the flash is set automatically to match the lens' focal length ranging from 24mm wide-angle to 85mm medium-telephoto. It also incorporates a built-in reflecting plate and diffuser that can be slid out from the top of the flash head for soft lighting effects. The bounce flash head can be tilted 90° upwards and can be swiveled 180° to the left and 90° to the right. In addition, the flash can also be set manually at 6 different power output levels or can be utilized as a wireless slave. The covering focal length of the flashlight can be seen on the LCD panel, and a flash ready signal can be seen in the viewfinder.Weights 9.5 oz without batteries.