The Canon ST-E3-RT provides you with seamless control over your creative flash photography. Radio-frequency control provides reliable operation even when direct line of sight is not possible. he ST-E3-RT makes complex lighting setups simple by facilitating radio-controlled, two-way wireless transmission up to 98.4' away, among up to five groups or fifteen individual Speedlites! The ST-E3-RT represents the next generation in wireless flash systems.
