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. Pentax – the Spotmatic Pentax was the first manufacturer to show a prototype camera with a behind-the-lens spot metering CdS meter system in 1961, the Pentax Spotmatic. Production Spotmatics, however, didn't appear until mid-to-late 1964, and these models were featured with an averaging meter system. Topcon – the RE Super Tokyo Optical's Topcon RE Super (Beseler Topcon Super D in the US), however, preceded Pentax into production in 1963. Topcon cameras used behind-the-lens CdS (Cadmium Sulfide Cells) light meters which were integrated into a partially silvered area of the mirror. Minolta – the SRT-101 with contrast light compensation Japanese-made SLRs from the mid-1960s (1966) included the Minolta SRT-101, and later the SRT-202 and 303 models, which used Minolta's own version of behind-the-lens metering which they referred to as CLC (contrast light compensation). Miranda and other camera manufacturers Other camera manufacturers followed with their own behind-the-lens meter camera designs in order to compete in the marketplace. 35mm SLR film cameras such as Miranda with their Miranda Sensomat, unlike most other systems used a behind-the-lens meter system built into the pentaprism itself. Other Miranda 35mm SLR cameras could be adapted to behind-the-lens capability through the use of a separate pentaprism which included coupled or non-coupled built-in CdS meters. Miranda had a second lens system, consisting of the Sensorex models which had an externally coupled auto diaphragm. Sensorex camera bodies had built-in meters and these evolved to include TTL and 'EE' capability. The 1970s – improvements in design, light metering and automation Design One of the most significant designs of the seventies for the 35mm SLR camera industry was the introduction of the Olympus OM-1 in 1973. After experiencing success with their small Olympus Pen half-frame cameras, particularly with their half-frame SLR-based Olympus Pen-F, Pen-Ft and Pen-FV cameras, Olympus set out with its chief designer Yoshihisa Maitani to later create a compact SLR—the M-1—with new compact lenses and a large bayonet mount that could accept almost any SLR design