[bryan conner]

My opinion concerning portraiture and shallow DOF/sharpness is this: sure, with any given lens wide open, the subject is not going to be as sharp as possible, but the "relative sharpness" will appear to be sharper than in reality due to the blurred background. I think that the most common problem with shooting wide open with a shallow DOF is the chosen point of focus. In a portrait, that usually should be the eye closest to the camera. If it is relatively sharp in comparison to the rest of the image, then it will appear sharp at a normal viewing distance...or at least, it will not look like a mistake.