Arrived a few hours ago so subject matter is mundane but impressed with the sharpness and speed of focus. Balances nicely on the GH1. All at 300mm full stretch (after all that's why I bought it). Straight out of camera jpg: This one has been PP using Perfectly Clear plugin in PS. This one also PP'd. We had strong winds and this is still sharp. At f/6.3 and ISO 100 still got 1/500 sec in our Oz sun.