Introduced in 1987, the
EF lens mount is the standard lens mount on the
Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens. Mechanically, it is a
bayonet-style mount, and all communication between camera and lens takes place through electrical contacts; there are no mechanical levers or plungers.