 When this camera appeared, a new range of FD lenses was introduced, with instant mounting/unmounting of the lens.This is called the New FD mount and does away with the older type of mounting ring which was fitted on to the rear of the lens and was awkward to use and needed two hands, to a newer, easier system whereby the user lined up the red dot on the lens, with the red dot on the camera and simply turned the whole lens clockwise until it clicked into place.All the other AE-1 accessories fit the AV-1.