Olympus M.Zuiko Digital ED 100-400mm F5.0-6.3 IS Lens - Brand New review
First off, there is no doubt that Olympus have produced a superb lens, both for ease of use and for features provided. Performance is also excellent, better than the bald figures suggest. The IS system works well, extending the usefulness of the lens as the light levels fall.
Very good sharpness, Low CA and distortion, Virtually no flare, Weather resistance, Very close focusing, Blisteringly fast AF, Lovely bokeh, Effective Image Stabilisation, Low vignetting, Excellent price, Supports Image Stacking, Tripod mounting collar, Light and Compact
Modest maximum aperture