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 three remaining FD-mount cameras it produced, the New F-1, T90, and T60. Using FD lenses on other mounts The 42mm flange focal distance of the FD mount is shorter than that of most other lens mounts. Therefore, some lenses from other period cameras with longer flange focal distance can be mounted on Canon FD-mount cameras with appropriate adapters and still retain infinity focus. FD lenses can be adapted to other cameras with longer flange focal distances, though the lenses cannot focus to infinity unless the adapter contains an optical correction element which may compromise image quality, as it is not part of the original FD lens optical design. Following the introduction of the EOS camera line, whose EF lens mount has a 44 mm flange focal distance, Canon briefly marketed an adapter which enabled certain FD telephoto lenses to be used on EOS bodies. The adapter contained high-quality corrective optics and functioned as a 1.26x tele-converter; it could not be used on lenses shorter than 200mm in focal length, nor any lens that interfered with its protruding optics. The adapter was produced in limited numbers, with the intent of easing the initial cost of conversion for professional users who owned expensive FD telephoto lenses. Originally priced at $250, these adapters are now scarce and highly valued, selling for around $1,000 on the second-hand market. Other inexpensive aftermarket FD to EOS adapters are available and can be used at the cost of severely reduced image quality, particularly at large apertures. Mechanically skilled photographers and technicians have successfully retrofitted FD lenses with alternative mounts, including the Arri PL mount and Canon EF mount. FD lenses can be mounted on Canon rangefinder cameras or other Leica screw mount cameras using the Canon Lens Mount Adapter B, but rangefinder-coupled focusing is lost. FD lenses have been regularly used with the Micro Four Thirds system since its introduction in 2008. It has