automatic and manual exposure units technical photography: data recording backs, endoscope and astrophotography adapters cases, grips, cable release, battery holders See also Four Thirds System Micro Four Thirds system, a derivative of the Four Thirds system specifically geared to digital mirrorless interchangeable-lens cameras (MILCs) Olympus OM-D series, the 2012 resurrection of the Olympus OM System References External links Olympus Chronology Olympus Corporation history page. OM system Lens mounts