K Series Pentax 645D
Three new models were introduced at once in 1975: the K2, KM and KX. The KM was almost identical in features and operation to the Spotmatic F. The KX featured a better TTL light meter using SPD (silicon photodiodes), visible aperture and shutter speeds in the viewfinder, and a mirror lock-up mechanism. The K2, the flagship model, incorporated aperture-priority autoexposure with a fully manually selectable range of shutter speeds from 8s to 1/1000. The only other aperture priority camera Pentax had made up to this point, the ES series, only had manual shutter speeds from 1/60 upwards. A special version of the K2 was also produced (called the K2DMD) to use a motor drive and data back. A later addition to the K series was the K1000 (basically a KM stripped of its self-timer and depth of field preview), later to find fame as the perennial camera of choice for photography students.