I bought this lens in early 90's, when I started using SLR for underwater photography. The underwater housing manufacturer (Hugyfot) recommended this lens over the Nikkor 15mm 3.5. My copy of the lens is supposed to be the Mk 2 version. It was a bit physical longer than the Mk 1, and it was supposed to be a little better. I used it for many years, but was never quite satisfied with it. It was the corners that were unsharp. Later I learned that the problem with mushy corners most likely was due to the dome port on the underwater housing, having too little radius. Then I got a new dome port with bigger radius, and image quality improved a lot. After I went digital in 2005, the lens was put away into deep storage.
After I got the Df, I started to wish for a super wide-angle lens. The old Sigma was brought out of hibernation. I went for a walk in order to take some test shots. One thing is the unsharp corners, but now I experience a lot more ghosting/flaring than I seem to remember from the film days. Even when photographing away from the direction of the sun, I can see some flaring/ghosting. This is orange spots at the outer part of the image.
Do anyone have experience with this lens? Is the Samyang 14mm better, or should I get a Nikkor 15mm f3.5 instead? Or a 18mm?