Sans Mirror  

The Olympus (and Panasonic) cameras use m4/3 mount lenses. m4/3 mount lenses have a 2x angle of view crop compared to 35mm and FX lenses. m4/3 mount lenses can only be used on Olympus, Panasonic, or other m4/3 cameras; they cannot be used on the original Olympus or Panasonic 4/3 cameras (i.e. these lenses are micro 4/3, not 4/3). 

Reminder: OM Digital Solutions is the spin-out company that took over the Olympus Imaging division.

Currently available OM Digital Solution m4/3 lenses:

Olympus’ Web Site for Lenses

OM Digital Solutions makes an adapter for the original 4/3 lenses, and the E-M1 camera, in particular, is very well suited to those lenses.