This lens was a demo model of sigma.
This lens has a very good build quality, similar to other art styles, maybe even better.
She's pretty sharp all over the image, I see little difference in sharpness between center and edge image.
I did a little comparison between this lens and the Canon 24-70 2.8L II. at 24mm.
The canon is sharper everywhere, from the center to the edge, even at f8.
I think this is not a disaster because I suspect that the canon variant, the 11-24, can't also stand the comparison at 24mm with the 24-70 2.8LII.
This lens seems a good connection on my 24-70, and mainly because of the price.
Here in Belgium, the price of the sigma is € 1,749, whereas' the canon 11-24 still costs € 3,000.
I'm going first read some reviews ...... but this lens is already in stock here.
The images above are raw images without any post processing.
At this site http://www.lenstip.com/ is already a review .