Take full advantage of all the features on compatible flashes with the third iteration of the Canon Speedlite Transmitter ST-E3-RT. This transmitter simplifies complex lighting setups by facilitating radio-controlled, two-way wireless transmission at distances up to 98.4' among up to five groups or 15 individual Speedlites. Wireless Rear Curtain Synchronization is available for capturing light trails and creating motion blur in your images. An expansive minimum output range allows you to stop down to 1/8192 for very low-light shooting. Another useful feature is FE Memory, which allows you to lock in an E-TTL flash exposure level, even in complex multi-flash setups, and subsequently continue to use it for the same scene or subject. Eight types of custom functions and three types of personal functions are included in the design. The LCD panel and backlit controls allow for easy operation even when you're working in dimly-lit environments.