Canon FD Lens Mount - FD Autofocusing and The AC Lenses

FD Autofocusing and The AC Lenses

With one exception, FD lenses were manual-focus lenses. In the mid-1980s, Canon also manufactured three unusual autofocus lenses for the FD mount standard.

The FD 35-70mm AF contained an entirely independent autofocus system and was the world's first autofocus zoom lens. The autofocus system was activated by a button on the side of the lens, and involved no communication with the camera body. It was reasonably accurate with still subjects, but was too slow to be a practical solution for moving subjects such as sports.

Further development into autofocusing produced the AC derivative of the FD mount. Three AC lenses were manufactured, the AC 50mm f/1.8, AC 35-70mm f/3.5-4.5, and AC 75-200mm f/4.5. All were released in April 1985 alongside the Canon T80 camera, which was the only camera ever manufactured to take advantage of the AC lenses' AF capabilities. The lenses communicated with the T80 via a modified FD mount with added electrical contacts. They lacked an aperture ring, and were therefore usable only in automatic-exposure modes. They were otherwise identical to the FD mount and could be manually focused on those FD-mount cameras that could control the aperture. The AC line proved to be a dead-end development in light of the EF series development, and Canon would abandon the capability in the two remaining FD-mount cameras it produced, the T90 and T60.