Overall, the lens renders excellent center sharpness from f2.8 to f8 and reasonably good sharpness at f1.8, f2, and f11. It noticeably falls off at f16 and is rather disappointing at f22. Note that the camera's maximum shutter speed at f1.8 wasn't technically high enough for a definitive result.
Overall, while there's similar softness at the corners as in the center, there isn't a substantial amount of distortion, except at f1.8. However, note that the camera's maximum shutter speed at f1.8 wasn't technically high enough for a definitive result.
(Tested with Olympus OM-D E-M5; cropped from upper-left corner)
