Features
The OM-4 uses a horizontal cloth focal plane shutter with a manual speed range of 1 to 1/2000 second (as long as 240 seconds in automatic mode) plus bulb and flash X-sync of 1/60 second. Unlike most SLRs of the era, the OM-4 used an Olympus OM-series standard shutter speed ring concentric with the lens mount instead of a top-mounted shutter speed dial.
The OM-4 accepts all lenses with the Olympus OM bayonet mount (introduced in 1972 with the Olympus OM-1). The contemporary Olympus Optical-made lenses were called "Zuiko".
The OM-4 is a battery-powered (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-meter (2% of view; 3.3˚ with 50 mm lens) and can take up to eight spot measurements and average them. Another unique feature was the possibility to spot the darkest or most illuminated part of the scene and the OM-4 would adjust the exposure based on that measure. The light meter uses a dual concentric segmented silicon photodiode to provide spot or centerweighted readings. It uses a graduated linear LCD shutter speed display at the bottom of the viewfinder to precisely indicate its readings versus the actual camera settings. The interchangeable focusing screen, delivered with the camera, had split-image rangefinder and microprism collar focusing aids.
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, flexible integrated circuit electronics.
Accessories for the OM-4 includes all the Olympus motor drives made for the OM-System cameras. Motor Drive 2 was introduced with the OM-4 and in addition to automatic film advance (up to 5 frames per second) features a motorized film rewind. The camera can take the Olympus 250 exposure bulk film back (10 meters of film = 250 frames) and the Olympus T system flashes. The T45 handle mount electronic flash (guide number 148/45 (feet/meters) at ASA/ISO 100) was also introduced with the OM-4.
The original OM-4 was available in only one color: all black. The introductory US list price for the body only (no lens) was $685. Note that SLRs usually sold for 30 to 40 percent below list price.
The camera dimensions are 87 mm height, 139 mm width, 50 mm depth and 540 grams (19 oz) weight.
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