Olympus OM-4

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 and as OM-4Ti from 1986 to 2002.

The OM-4 was the successor to the OM-2N and represented the highest evolution of the Olympus OM-series SLRs (introduced in 1972). Other Olympus OM top models were the OM-1, OM-2, OM-1N, OM-2N, OM-2 Spot Program, OM-3 and OM-3Ti. They all used the same body configuration, but with developing aluminum alloy chassis, electronics, feature levels, and external controls and cosmetics.

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 a battery-dependent (requiring two 1.5-volt silver oxide SR44, V76, 357 cells - use of a 3-volt 1/3N lithium cell is not recommended) electro-mechanically controlled manual-focus SLR with manual exposure control or aperture-priority auto-exposure.

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 center-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.

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