In case anyone anyone is looking to get an ultrawide I went out this weekend and bought this.
I was considering the Nikkor 14-24mm, but I wanted a wider available shot than the 14mm was able to offer, so bought this.
Just a trial shot today to check it as I am off to shoot a gig tonight in Barnstable, and wanted to make sure it was ok.
Very impressive, ok it is a 2k lens but at £550 it is a reasonable price to pay, the build quality is superb (I am a Sigma user along with Nikkor), I am also an avid user of UV filters for protection, so the lack of ability to fit one is a concern, especially with such a large piece of front glass, also this makes the use of filters hard. You can get a screw in tripod bust adaptor and place the filter in front of the lens but that is not great, luckily I don't use filters much in my shooting.
It is a heavy lens even though it doesn't look it, it is however as I said the build quality that is great.
I will buy a different lens when I finally get the D4s but for cropped sensors this is a superb addition.
The no filter is fairly typical of the ultra-wide angle lenses. I own four; a f/ 3.5 8mm Samyang Fisheye and a f/2.8 11-16mm Tokina for DX format, a Nikkor f/2.8 14-24mm and a Leica f/2.8 19mm Elmarit-R full-frame / FX. Of these, the Tokina is the only one that can take a filter. These lenses are so wide that a filter will cause vignetting, which is why they can't take one.
The lens hood on the Nikkor and Samyang are integrated into the lens (i.e. they are not removable) and the Samyang has a bit of vignetting from the hood, usually easily removable in post.
This lens was not avaiable when I was in the market for an ultra-wide, but had it been I would have given it a good hard look. The major downside for the way I tend to shoot (often building interiors at lowest ISO that I can get away with) is that at a maximum aperture is only f/4.5 (down to f/5.6 at 16mm), so this lens is a bit slow for my taste. That 1.5 - 2 stop difference versus a f/2.8 bothers me.
Just a very quick comment, I agree Sigma are great lenses although heavy. I have a Sigma 10-20 which I use on a Nikon D40 and am very pleased with the results, it is actually my favourite lens. I bought a set of filters on line but apart from keeping a UV on the lens, I find the polarizer quite fiddly to use. Have fun with the new lens.