pentax mx 35mm slr film camera f 2.8 40mm pancake lens. motor winder. pentax the pentax mx was a 35 mm single-lens reflex camera produced by asahi optical co, later pentax of japan between 1976 and 1985. it was pentax's flagship professional slr camera. the mx was solidly built, and featured a fully mechanical construction, including a mechanical shutter of the horizontal cloth type. only the light metering system was dependent on batteries. the mx is all manual: it does not feature autofocus or autoexposure modes such as aperture-priority, shutter-speed priority, or full program.