YONGNUO ST-E2 Speedlite Transmitter for 430EX 580EX II E-TTL/E-TTL II wireless flash system Ultra-AF: Improves the assist focus function, the max. focus distance can reach 25 meters. Access to Camera menu: You can set the relevant parameter of speedlite through access to the camera menu. Support Exposure compensation: You can adjust the power output of the speedlite by using the flash and exposure compensation to make the photography effect meet your requirement. Support Exposure Bracketing ( FEB ): Access to the camera menu to set the exposure bracketing function, it can help you to improve the success rate of photography. Overheating Protection: If the controller is used too frequently, it's overheating protection function will be triggered, the ETTL and HSS indicator will blink alternatively, and the controller will be locked.