The Canon Speedlite 600EX II-RT is the most powerful Canon system flash. Guide number 60 is sufficient for everything you want to illuminate with this type of flash. Does TTL and HSS Sync with current Canon cameras. Can work with other Canon flashes in the group. Advantages: Radio trigger with 30 m range Up to 15 flash units can be used together Integrated optical receiver Camera Remote Shutter Release Rotatable flash reflector with 20-200mm zoom function Guide number 60 (m, ISO 100, at 200 mm) White balance correction filter Quick and quiet charging Automatic exposure control E-TTL II/E-TTL/TTL FP short time synchronization yes Manual/output settings yes - 1/1-1/128 Manual steps 1/3 steps Strobe/output settings yes - 1/4-1/128 Frequency1-500 Hz (199 Hz when using the optical slave function)