The Olympus OM System was a line of 35mm single-lens reflex cameras, lenses and accessories sold by Olympus Corporation between 1972 and 2002. The range was designed by Yoshihisa Maitani, chief designer for Olympus, and his staff; OM stands for Olympus Maitani. The nucleus of the system was a series of compact bodies divided into an advanced series and a later consumer-oriented series. The first model was the all-mechanical M-1 which, after pressure from Leica (which already had an M1 model), was renamed OM-1. At the same time the M system was renamed OM System. The camera included a full-aperture TTL Cadmium-sulphide (CdS) exposure meter, and a bayonet lens mount of relatively large diameter. By the end of the 1970s it was joined by the semi-automatic OM-2 and consumer-oriented OM-10. Olympus continued the naming pattern with the 'professional' OM-3 and OM-4, and the consumer-level OM-20, OM-30 and OM-40. The cameras were accompanied by a series of Zuiko-branded lenses, as well as a generous selection of accessories. The majority of OM bodies and lenses were manual-focus only; the OM-707 of 1986 was the only true autofocus model.
Camera models Olympus produced a wide variety of OM camera models over the years. These were divided into two distinct series. Cameras with single-digit model numbers were the 'professional' series, optimized for more advanced features and durability. Two-digit (or more) model numbers, or letters, meant a 'consumer' camera designed for ease of use. All the consumer-grade models were discontinued after 1992, since the market for manual-focus SLR cameras had declined greatly in favour of autofocus SLRs. The consumer line returned in 1997 with the Cosina-sourced OM-2000 model. Professional and advanced-amateur demand for the high-end models continued, and they were produced until 2002, along with the consumer-grade OM-2000.
Professional cameras
OM-1
The Olympus OM-1 was a manually operated 35 mm single-lens reflex camera forming the basis of the OM system in 1972. At first called the Olympus M-1, Leica disputed this designation and it was changed to OM-1. It was designed by a team led by Yoshihisa Maitani with a through-the-lens exposure meter controlling a needle visible in the viewfinder. It was noted for its reduction of size, weight and noise. One feature unique to the OM-1, compared to the rest of the OM system, was its mirror lock-up facility which made it ideal for astrophotography and macrophotography.
OM-2
Introduced in 1975, the Olympus OM-2 was a semi-automatic, aperture-priority camera featuring an electronically controlled shutter. It was based on the OM-1 body, and retained compatibility with OM-1 accessories and lenses. It boasted automatic through-the-lens (TTL) off-the-film (OTF) metering, and exposure was considered very accurate. This was calculated by the measured light reflected off the surface of the shutter, and/or the film surface during the actual exposure. The camera also offered a manual-exposure mode, as in the OM-1. It also introduced the integration of electronic flash into the exposure system using the TTL exposure system.
OM-3
The OM-3 was an updated version of the OM-1, a manual camera without automatic exposure modes, and an entirely mechanical shutter. It featured a multi-spot metering system (shared with the OM-4) in addition to the centre-weighted metering of the earlier body. It also featured an LCD similar to the OM-4 which could be illuminated in low light. Its main advantage over the OM-4 was its ability to operate without batteries due to its mechanical design. Batteries were only needed for the exposure meter and LCD. It lacked a self-timer and mirror lock-up functions, however. In 1995, nine years after the OM-3 was discontinued, the OM-3Ti was released. It shared the improvements over the OM-3 that the OM-4Ti held over the OM-4.
OM-4
The Olympus OM-4, an improved version of the OM-2, was manufactured from 1983 to 1987. It was introduced at a US$685 list price for the body alone. It was a battery-powered, electromechanically controlled, manual focus SLR with manual exposure control or aperture priority autoexposure. It used a horizontal cloth focal plane shutter with a speed range of 240s (in auto mode) to 1/2000s plus bulb, and flash X-sync of 1/60s. The OM-4 featured a built-in spot meter [of a narrow acceptance angle, see Canon FTb] (2% of view; 3.3˚ with 50 mm lens) and was the first camera capable of measuring eight individual areas and averaging them. The light meter used a dual-concentric segmented silicon photo-diode to provide spot or centerweighted readings. It used a graduated linear LCD for the shutter speed at the bottom of the viewfinder to precisely indicate its readings versus the actual camera settings. In 1986 the OM-4 was improved to a tougher OM-4Ti (OM-4T in USA) version, with titanium top and bottom plates, improved weatherproofing and high-speed flash sync. This last version was discontinued in 2002.
Consumer-grade cameras
OM-10
The OM-10 hit the markets in June 1979 at the same time as the OM-2N. The camera was a 35mm focal-plane shutter aperture priority AE SLR camera with an electronic shutter. Only aperture-priority AE was available with the camera unless the optional manual exposure adapter was installed. This allowed the setting of shutter speeds between 1s and 1/1000s, (bulb mode was also available). The camera was equipped with a fixed pentaprism viewfinder which contained an LED exposure indicator. The finder coverage was measured to be 93%. A mirror-lockup facility was integrated into the self-timer function. Exposure control was aperture priority AE using center-weighted light metering. Film speeds of the camera range from ASA 25 to ASA 1600. Film winding was done by using the film-wind lever located on the top right of the camera. Film rewinding was done manually using the film-rewind crank located at the top left. The camera body measured 136 × 83 × 50 mm and weighed approximately 430 grams (15 oz).
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