Olympus's ultra-wide for original Four Thirds — 18-36mm equiv, predecessor to the MFT version.
The Olympus Zuiko Digital ED 9-18mm f/4-5.6 is an ultra-wide zoom for the Four Thirds DSLR system (not Micro Four Thirds). Designed for Olympus Four Thirds-mount DSLR bodies including the E-1, E-3, E-5, and E-30. Covers approximately 18-36mm equivalent. Four Thirds mount.
f/4-5.6 variable aperture. 9-18mm zoom range (approximately 18-36mm equivalent on Four Thirds 2× crop). ED (extra-low dispersion) elements. At approximately 155g. 52mm filter thread. Four Thirds DSLR mount (not Micro Four Thirds).
The Four Thirds system is a DSLR mount distinct from the Micro Four Thirds mirrorless mount — although the sensor size is the same, Four Thirds has a deeper flange distance and different mount diameter. Four Thirds lenses require an adapter (MMF-1, MMF-2, or MMF-3) for use on Micro Four Thirds bodies, where phase-detect AF may not function at full speed.
On the used market the Olympus Zuiko Digital ED 9-18mm f/4-5.6 is an ultra-wide for Four Thirds DSLR cameras. Condition checks: Four Thirds mount contacts, AF response on native Four Thirds body, 52mm front element for marks, zoom ring smoothness. Four Thirds mount — adapter required for MFT use.