For wireless Speedlite setups requiring one or more off-camera flashes, the Speedlite Transmitter ST-E10 delivers a transmitter compatible with EOS cameras that include the multi-function shoe. Since this transmitter maintains a digital connection to the camera through the shoe, it does not require batteries, making the design approximately 30% smaller and approximately 50% lighter (than the ST-E3-RT II). Controlling and changing the 5 independent groups across 15 Speedlites is as easy as pressing the menu button located on the transmitter and adjusting the settings from the vari-angle touchscreen on the back of the camera, or with the flash setting screen when using the Canon Camera Connect app on your smartphone. With full flash control at your fingertips, the Speedlite Transmitter ST-E10 is an indispensable tool for advanced, professional flash photography.