(Canon) Electro-Focus. Canons designation for the EOS bayonet lens mount system. EF-compatible lenses are, therefore, designed to fit EOS cameras and do not fit any other camera bodies.
EF lenses have an internal diameter of 54mm and an external diameter of 65mm and are the largest lens mounts of any 35mm system. They are purely electronic - there are no mechanical linkages of any kind. While the EF system has been standardized since 1987 there was a digital-oriented variant known as EF-S introduced in 2003.
cf. bayonet, EF-S, EMD, EOS, lens mount.
Entry last updated 2004-02-11. Term 402 of 1487.
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