History Canon EF lens mount

number of canon ef lenses sold on time (red), compared nikon f mount lenses (blue)

the ef mount replaces predecessor, fd mount. standard autofocus lens mounting technology of time used motor in camera body drive mechanics of focus helicoid in lens using transfer lever. key innovation of ef series use motor inside lens focusing. allowed autofocusing lenses did not require mechanical levers in mount mechanism, electrical contacts supply power , instructions lens motor. motors designed particular lens installed in.

when ef mount introduced in 1987, had largest mount diameter (54 mm internal) among 35 mm slr cameras.

the ef series includes on eighty lenses. ef series has encompassed focal lengths 8 1200 mm. ef-m mount introduced 2 lenses, 22mm prime , 18–55mm zoom. many ef lenses include such features canon s ultrasonic motor (usm) drive, image stabilization system (is), diffractive optics (do) and, particularly l-series lenses, fluorite , aspherical lens elements.