The lens nets outstanding resolution for the 20MP sensor at 100mm (2,650 lines), with strong resolution from center to edge.

I'm speculating here, but perhaps it was for size or cost-saving factors not to utilize the same high-precision gyro sensors as the 300mm?aperture is likely introducing a slight bit of diffraction-related softness, as images didn't seem as tack-sharp as they were with the bare lens. IS lens is capable of 200-800mm equivalent1 telephoto shooting on its own, which can be further extended when paired with the optional (sold separately) M. That being said, if you can manage to position yourself so that your subjects is far away from a background, you can get a very pleasingly smooth, blurry background and nice subject isolation.

I did notice slight drop in sharpness when you zoom past 300mm, and especially at the furthest end of 400mm, but to be entirely honest, even at 400mm, the lens is still nothing short of spectacular. You get great build quality, the lens is made of part metal and part plastic, very well constructed I must say, you can feel it as you handle it with your hands. Okay, it didn't quite go like that, but after waiting a week to get the lens in my hands, that pretty much sums it up. Though I must admit, if there is a side by side comparison, I'd still be able to see the minor difference, and the PRO lenses still have the advantage in optical superiority.The Olympus range of micro four thirds cameras is designed around portability and this lens cements this, as well as Panasonic Lumix G compatibility, as a truly lightweight system.