The Olympus OM-2 is a single-lens reflex film system camera produced by Olympus of Japan. It is part of the Olympus OM system.

OM-2 is the automatic version of the OM-1, presented officially in 1975 at the 31st Photo Salon in Paris. An OM-2 prototype was displayed in a showcase at the 1974 Photokina in Cologne, but none of its features were announced. Externally it is nearly the same as the OM-1, but the shutter is electronic and the exposure is either automatic (aperture priority) or metered-manual.

When the switch is in “off” position, the shutter will still fire in aperture priority mode, but with the speed limited to about 1/30th or above to save battery, and there will be no metering indication in the viewfinder — this is because the OM-2 has two sets of metering cells: those used to passively indicate the exposure information to the photographer, and those which are active during aperture-priority operation. When the camera is off, the former set of cells are deactivated, but the latter set will still be activated during exposure.

The reason for the two sets of cells is this: while the former allow the exposure to be previewed for the photographer in both automatic and manual modes, the latter set actually determine the exact exposure in automatic mode. They are pointed backwards towards the shutter. The shutter curtain has a computer-generated pattern of white and black squares on it, representing a mathematically “average” photographic scene. Reflected light coming off this pattern allows the camera to meter the exposure when the mirror is up.

When short speeds are indicated, the only significant metering is that done by reflected light off the curtain, as on the Leica M6. When longer speeds are indicated, (1/45th sec and longer) the camera will continue metering reflected light off the surface of the film and compensate for any variation of light; this is called off-the-film (OTF) metering.

There is a transparency held to one side of the focusing screen, with the shutter speed and two arrow marks which serves as the indicator for the meter needle: when in automatic mode, this transparency is slid mechanically all the way into frame and the needle shows the shutter speed that the preview cells anticipate will be selected. In manual mode, a small tab on the edge of the transparency is slid into the frame, showing the two arrow marks. Centering the needle between these two marks gives metered exposure using the preview cells, without involving the OTF cells. When the camera is in “off” mode, the needle is relaxed and the transparency is slid completely out of sight.

There is no AE lock-instead, the dial on top of the camera has been replaced with an exposure compensation dial (the film speed is set by a smaller dial inside this one, as on the shutter speed dials of many SLR’s) which essentially allows the photographer to change the exposure by a certain amount by changing the metered film speed without losing track of the actual film speed. This is often necessary for backlit subjects in conditions where it is inconvenient to use manual mode to compensate for the backlighting.