This page compares the behavior of the Nikon AF-S 85mm f/1.4G to the Nikon AF-S 85mm f/1.8G, with a view towards deciding on one or the other for a classic head and shoulders portrait, in terms of getting sharp eyes in the ƒ/2.8 - ƒ/4 range. The hope is that that 85/1.8G will offer superior sharpness due to less severe focus shift. See the prior focus shift study of the Nikon 85mm f/1.4.G.
Lens sharpness is not the issue—both 85mm lenses are very sharp— focus shift is the issue. Focus shift and how to mitigate it are discussed in detail in Making Sharp Images.
The 36-megapixel Nikon D800E was used for its superlative sharpness (quite amazing having just finished testing the Leica M9 on the same scene). Distance from camera to scene was about 2 meters, using DX mode to crop off extraneous material. This is roughly the distance for a head and shoulders portrait.
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