I discovered something peculiar this morning while testing a 200MM AIS on my D3s. I was focusing on a distant object visually, it focused just short of infinity. Focus confirmation lit up at infinity. I compared the two images and the visually focused one was soft, the focus confirmed image sharp. I then tried the same routine with a Sigma 105MM at a distance of about 6 feet. The visually focused image was slightly soft, the AF image was sharp and the focus confirmed image was sharp. I checked the diopter, all was fine. Is the Nikon prism not accurate in general or is it just my particular camera?