Canon EF lens mount

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Canon EF mount

The electronic contacts (gold-plated) of an EF mount lens.
Type	bayonet
Inner diameter	54 mm
Flange	44 mm

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. The mount was first introduced in 1987.

Canon claims to have produced its 100-millionth EF-series interchangeable lens on April 22, 2014.^[1]