The new Canon Speedlite 90EX is a small flash originally designed for the EOS M camera systems but are compatible with any EOS camera. It's best use is as a fill-flash. Don't expect this to over power the sun! The flash can work as wide as 24mm and can control other flashes through optical triggering. Flash options are controlled through your camera. Guide number of 30 ft @ 100 ISO. Takes 2 "AAA" batteries.