Olympus OM4 35mm Film Camera with Zuiko 50mm f1.8 Prime Lens
The Olympus OM-4 is an interchangeable-lens, 35 mm film, single lens reflex (SLR) camera; manufactured by Olympus Optical Co., Ltd. (today Olympus Corporation) in Japan, and sold as OM-4 from 1983 to 1987.
The OM-4 used a horizontal cloth focal plane shutter with a manual speed range of one second - 1/2000 second (up to 240 seconds was possible in automatic mode), plus bulb and flash X-sync of 1/60 second. Unlike most SLRs of the era, the OM-4 used a familiar OM-series shutter-speed ring, concentric with the lens mount, instead of a top-mounted shutter speed dial.
The OM-4 accepted all Olympus-made OM bayonet-mount lenses, which were marketed under the Zuiko brand name.
The OM-4 was the first camera with a built-in multi-spot exposure meter (2% of view; 3.3˚ with 50 mm lens) which could take up to eight spot measurements and average them. Another unique feature was the selectable option to assess the darkest or brightest part of the scene, the camera adjusting the exposure based on that measure.
The light meter used a dual-concentric segmented silicon photodiode to provide spot or centre-weighted readings. It used a graduated, linear LCD shutter speed display at the bottom of the viewfinder to precisely indicate its readings versus the actual camera settings.
The major improvements of the OM-4 compared to the OM-2N were the stronger chassis, gasket weatherproofing, permanently affixed, dedicated hot shoe and TTL flash cable connector, linear liquid crystal display (LCD) shutter speed display, provision for spot-metering, and flexible integrated-circuit electronics.