Lenses for the earlier Canon FD lens mount are not usable for general photography on an EF or EF - S mount camera , .
Adapters with optical elements are used because they are made for a flange focal distance of only 42.0 mm .
Lenses for the earlier Canon FD lens mount are not usable for general photography on an EF or EF - S mount camera , unless adapters with optical elements are used because they are made for a flange focal distance of only 42.0 mm .