Speedlite EX

Speedlite EX

Canon Inc.'s EOS flash system refers to the photographic flash mechanism used on Canon's film (35mm and APS) or digital EOS single-lens reflex cameras. The line was first introduced in 1987. It has gone through a number of revisions over the years, as new flash exposure metering systems have been introduced. The main light-metering technologies are known as A-TTL, E-TTL, and E-TTL II.

The EOS flash system is capable of wireless multiple flash control, whereby a master flash unit IR (ST-E2) or RF (ST-E3-RT) transmitter mounted on the camera body can control up to 3 (optical) or 5 (radio) groups of flash units. The Canon EOS 7D is the first Canon body to be able to control Speedlites wirelessly without the use of a Master Speedlite or IR transmitter; three other EOS models, the 60D, 600D and 650D, also have wireless flash capabilities. The 7D is the only one of them being able to handle three slave groups. The other cameras can handle two.