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. 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. Accessories for the OM-4 included 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), featured motorized film rewind. The camera accepted 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.