A 50% screen grab showing focus point as the red box (Nikon ViewNX feature), note how soft key is. Observe ruler for the sharpest point, approx. 2 cm behind the focused distance! This shot taken WITH the normal Hoya UV filter fitted. This is one of a pair of images to prove the filter was not contributing in any way to the problem. The lens is Sigma 18 - 250mm f3.5-6.3 DC OS HSM