in 1972, the nikon f2 was introduced. it had a more streamlined body, a better mirror-locking system, a top shutter speed of 1/2000 of a second and was introduced with its own proprietary, continually improving photomic meter prism heads. this camera was constructed mechanically superior to the f, with some models using titanium for the top and bottom cover plates, and featured slower shutter speeds via the self-timer mechanism. all nikon f and f2 photomic prism heads coupled to the shutter speed dial of the respective camera, and also to the aperture ring via a coupling prong on the diaphragm ring of the lens. this design feature was incorporated into most auto nikkor lenses of that time. nikon technicians can still install a coupling prong on d type auto nikkor lenses so that these newer lenses will fully couple and operate with the older nikon camera bodies. this is not possible with the g type auto nikkor lenses and lenses with the dx designation.