Canon developed EOS system in 1987. This system incorporates fully electronic mount system that controls AF (auto focus) drive electronically by a driving motor in the lens, and aperture diameter control by the electronic signal from the camera body. This mount system realizes fully electronic control of all data transmission and control, eliminating any mechanical drive or data transmission. This system assures faster and more accurate interactive communication without any loss. The EOS system provides many benefits including;
1. high operational reliability because of no mechanical power and data transfer mechanism at the mount section.
2. high-speed and high-precision lens drive for autofocusing.
3. high-precision control of aperture diameter by the EMD.
4. realization of TS-E and IS lenses because of electronic contact.
5. high versatility of accessories, including Extenders.