Due to some negative reviews I was initially unsure if I should buy this super wide angle to me. Much has already been said in other reviews, my serves as a comment or to confirm. First test: Vignette: Yes, available but not as disturbing as some of users described. Wide-angle lenses have a certain physical reasons Randabdunklung. Depending on the subject, you can leave it like that or you need to brighten the corners via software. I think now, after some testing even that the vignetting is low. Even when shooting with a lot of sky I suppose they often do not even notice. Those who claim to look through a tube, did not understand the instructions. The adapter for the cap has to be removed. This is also my first (small) gripe, I would have a cheaper Aufstecklösung plastic like better. Now you have two parts (adapter and lid). I fear, in the long term the metal adapter will scratch the lens hood, and it is also a bit fiddly. Maybe Sigma thinks again after more than a cheap accessory. In initial hence the incorrect operation would be excluded by some users, and the metal adapter could give it as an accessory. The adapter bothers me now so much that I have turned directly to Sigma, maybe it helps. Distortion: Barrel distortion is clearly visible, but also so that it will be able to live with a number of motives. If not, the image processing needs help. Second and subsequent tests: The vignetting I feel now even to be very low for a lens of this focal length. Also chromatic aberration is noticeable, but also not a problem. With the focus I am also satisfied, that is not as critical to see, because you do usefully rare enlargements, you want much in the picture have (with a telephoto lens is often different). Whoever criticizes the edge blur, worrying about the causes have to do. If you do a close-up with 28 cm distance, so there is the edge of the imaged plane at 12 mm focal length already in 49 cm distance, in the corners, it is even more. Because the image can not be sharp. This error also occurs when one scans the available test panels. With the wide-angle needs up close and then the corner is much further away and is out of focus. This is elementary geometry and no lens error. At great distances the corners are sharply focused, in any case my demands are met. The defects are minor and when you consider that this is a super wide angle lens, so there are not really, because the error of such lenses are typically and partially inevitable. Sigma would certainly have to reach about 10% improvement for 100% weight and price premium. Without mistakes there's more, here the designers have a balanced, good compromise.
