Originally posted by sheld At photozone.de, the DA15mm bests the DA14 at all apertures in the center and the corner of the image. At F/8, the DA15 bests all of the zooms, the DA12-24mm, the DA16-45mm, and the DA16-50mm, in the center and the corners
I have taken thousands of pictures with the DA 12-24, and hundreds with the DA 15 and the DA 16-45, and I can find no issues with the DA 15's corners compared to those other lens, even at wider apertures. In real world use, the DA 15 produces images with slightly more clarity at large print sizes than the zooms; at smaller print sizes (10" by 15'' or smaller), it would, howevre, take a very practiced eye to notice any real differences in the output of these lenses.
I suspect as well that the photozone results test only at a single distance, rather than multiple distances. Just because a lens is sharp corner to corner at 10 feet doesn't mean it will retain that corner to corner sharpness at longer distances, especially if we're talking about a zoom lens that involves the inevitable optical compromises that come with that sort of lens. At longer distances, the impressive corner to corner sharpness of the DA 12-24 tends to diminish, so that at 50 or 70 feet the DA 15 is clearly sharper in the corners (as is the DA 16-45).
However, none of this is really all that important, as most people aren't going to notice that the corners are not as sharp as the rest of the image. At large print sizes, people rarely look at the corners. Photographers need to print their best images and show them to non-photographers to gain perspective on what really matters. The sort of manias that afflict too many photographers (such as the mania for corner to corner sharpness and the mania for narrow DOF) don't generally afflict non-photographers, who tend to be more interested in the subject of the photograph, rather than the degree to which the image exhibits the technical prowess of the equipment used in making it.