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 original Four Thirds system (not Micro Four Thirds), covering 18-36mm equivalent. It was the predecessor to the MFT M.Zuiko 9-18mm series.
Optically good for the Four Thirds system — compact ultra-wide with ED glass. Variable f/4-5.6. The Four Thirds mount requires an MMF adapter for use on MFT bodies — adding bulk but maintaining AF.
Four Thirds mount — requires MMF adapter on MFT bodies. 72mm filter thread. Compact and lightweight for an ultra-wide zoom. The retractable design on the MFT version was not present on this Four Thirds original.
Available used very cheaply. The MFT M.Zuiko 9-18mm versions are more practical on MFT bodies — no adapter needed. For Four Thirds body owners or adapted MFT use. The adapter adds size and weight.