Type: 35mm Single Lens Reflex
Lens Mount: Olympus OM Mount, bayonet type.
Shutter: Focal plane shutter, ring mounted control, with speeds from 1 to 1 /1000 second plus B.
Hot Shoe Socket: Built-in. Accessory Shoe 1 or "Fixed" Type for original M-1 or OM-1 bodies.
Flash Contacts: FP-X with switch type contact at synchro socket, X contact at shoe: With electronic flash (X) 1 sec to 1/60 sec; with class "M" Bulbs (X) 1 sec to 1/15 sec; with Class "F" Bulbs (X) 1 sec to 1/15 sec; with focal plane Bulbs (FP) 1/60 sec to 1/1000 sec.
Viewfinder: Pentaprism type wide-vision (97% of actual picture field) finder.
Viewfinder Magnification: 0.92X at infinity with 50mm lens
Viewfinder Apparent Field of View: 23° 30' & 35°
Focusing Screens: Standard screen,1-1 Microproism-matte type. Interchangeable with any 13 additional screens.
Reflex Mirror: Quick return type with mirror Lock-up control.
Film Loading: Easy loading (Olympus EL system)
Film Advance: (Manual) Ratchet type film advance. One stroke or several short strokes. (Motor Drive with MD and OM-1n model only)
Film Rewinding: Rewind crank with automatic resetting rewind release lever.
Metering: Via Lever on top panel, Metering ON/OFF Switch
Exposure Measurement: Two CdS (Cadmium Sulphide) cells located on either side of the eyepiece provide through -the-lens open aperture light measurement.
Film Speed Range: ASA 25-1600
Exposure Range: EV1.2-EV16.9 with 55mm f1.2 at ASA100; EV 2-17 (ASA 100 with F1.4 50mm lens); EV2.35 - EV17.35 withh 50mm f1.8 at ASA100.
Self-Timer: Lever system with rortation angle 180°. Approx. 4-12 second delay lever type; Action started via start lever hidden behind Self timer lever. It can be stopped and reset after actuation.
Camera back: Removable hinge type control by Mounting Pin. Interchangeable with Recordata Back 1/2 /3 (OM-1n) and 250 Film Back 1/2.
Tripod Socket: As per JIS standard
Battery: 1.35V mercury battery Mallory PX625, or equivalent .
Dimensions & Weights: Body only: 510g, Body with f/1.8 lens: 136mm x 83mm x 81mm 680g.