The Speedlite 600EX-RT takes the best features from existing models and adds functionality for enhanced digital photography. The 600EX features a new wireless multiple flash system using radio wave communication that provides more precise control over as many as five groups of flashes. There's also more power, with a guide number of 197' (60 m) at ISO 100, a zoom flash head that covers a 20-200mm range, and updated AF assist beam that's compatible with Canon's 61-point High density Reticular AF.
The flash supports all current versions of TTL, including evaluative E-TTL II. This is great for photographers who shoot high contrast or reflective subjects, like those encountered in wedding photography. Photographers can now capture every detail from the black of tuxedos to the white of wedding dresses.