Olympus OM is a bayonet type mount used in 35mm SLR cameras.
The OM mount offers really good ergonomics and overall quality, especially with Olympus made lenses as they “graded” their lenses by their maximum aperture and not build quality.
Olympus lenses carry the Zuiko name. Until around 1980 the letter before Zuiko denoted the number of elements in the lens.
e.g. F.Zuiko – 6 elements. E.Zuiko – 5 elements.
Most OM lenses have a 49mm(compact and small) or 55mm(faster aperture) filter thread.
History… in short
The OM mount has a large mount diameter, which allowed for easier production of lenses with a fast maximum aperture.
Olympus film cameras were split into:
- Professional cameras with single digits in their name: OM-1, OM-2, OM-3, OM-4
- Consumer cameras with double digits: OM-10, OM-20, OM-30, OM-40.
Olympus OM was the only manufacturer to use the OM mount. (I cannot find information of others using it, email me if I’m wrong)
I love the ergonomics of the OM series. One of my all time favorite cameras is an Olympus OM-2n.
Olympus was the primary manufacturer of OM lenses, boasting a large selection of lenses from wide-angle, telephoto, zoom and macro to fisheyes.
Third party lenses in the OM mount were usually manufactured in all major lens mounts, so are not unique to this mount
E.g. Soligor, Vivitar, Tamron Adaptall