I tested my brothers Nikon 200-400mm F4 Lens. It's awesome. My OM-D E-M5 looks ridiculous on this monster. I used a Fotodiox adapter, which makes the lens completely manual. A tripod was a must for this beast. I also included a shot taken with my Konica 135mm F3.2 for comparison. I can't justify this lens at $6,700, although the Olympus 4/3 300mm must be incredible too, at about the same price range. On a side note, Fotodiox made a mistake when I ordered a konica adapter, and sent a Nikon adapter instead. It took awhile to sort this out, and Fotoddiox eventually told me to keep the Nikon adapter, and sent the Konica adapter. Good service.