Comments about Sigma Sigma 50mm f/1.4 EX DG HSM Auto Focus Lens for Nikon AF Cameras - U.S.A. Warranty:

This lens is best for portrait use due to its great bokeh and peculiar focus quirks. On my Nikon D700 @ f/1.4, AF fine tuning differs by both distance and focus point used. At 6 feet, the center is nearly accurate with a +1 adjustment; however, the far left and right focus points require a -20 adjustment. At 2 feet, the center point requires a +7 adjustment while the left/right focus points are still around -16. When only 1.5 feet away, the center focus point is +13.When I called Sigma, they said that the focus will vary by distance; however, they were surprised by the difference with the outer focus points. They said do not expect a big difference by exchanging the lens for another sample. They could offer no guarantees on fixing the lens either. In other words, that's the way it is.[...] I can obtain consistent results by turning on and off Nikon's AF Fine Tune depending upon the focus point used. However, I am not sure I want to go through the continuous hassle.