The Canon EF Lens System
Canon introduced it's new EF mount for the new line
of EOS cameras in 1987, with the unveiling of the EOS 650. What followed
was a series of automatic exposure, auto focus, computer controlled electronic
cameras. Much of the technology was premiered in the Canon A series of
cameras, which had used the old FD series of lenses, but did feature a
digital viewfinder, and multi-mode exposure system. One new feature, which
had not been on a previous series of Canon cameras, was auto focus. Though
the Canon AL-1 had included a focus indicator, in the form of a circle
and a pair of arrows, indicating when proper focus was acheived, it had
not been linked to the focusing mechanism of the lens.
Unlike the old FD, FL, and R series of lenses, the
new EF type was designed with no mechanical linkages to the camera. Instead
each lens has a small digital chip, and motor, and a series of pins connecting
to a data bus on the camera's lens mount. The lenses feature a bayonet
mount which requies a quarter turn to lock or unlock.
this is not the first time Canon changed it's lens mount.
R, FL, and FD, plus new FD
The two lines coexsisted for a time, but in 1992 canon production of
FD lenses ceased.