The Canon FD system was introduced in 1971. Early FD lenses use a breech-lock system to attach to cameras, but later New FD or FDn lenses mount similarly to other manufacturers. Despite this difference, all FD lenses are compatible with all FD bodies. One of the improvements of the FD mount over its predecessor, the FL mount, was the introduction of an automatic aperture system. This allows the user to focus wide open, then have the camera stop down automatically before taking the picture.
Over its two decade production run, Canon introduced 134 different lenses for the FD system, ranging from 7.5mm to 1200mm. One of the most popular cameras in the FD system is the Canon AE-1 Program which sold well over a million units during the 70’s and 80’s. FD lenses are regaining popularity with the rise in mirrorless digital camera users, since they are easy to adapt to mirrorless systems and offer excellent image quality for their price.