At photokina 2012 Sigma announced a new "Global Vision", which divides their lens portfolio into 3 categories: "Contemporary", "Art" and "Sports". These product lines don't apply to existing Sigma lenses, but any newly developed lens will be assigned to one of them, giving a rough guidance about the intended purpose of a lens.
The first lens that carries the "Art" tag is the 35mm f/1.4 DG. Sigma already has some experience in building fast prime lenses, a market segment that has not seen much contribution from 3rd party suppliers in the past. Just like their other full frame primes, the EX 50/1.4 and the EX 85/1.4, the new Art lens competes with the original manufacturer's products. Since we're looking at the F-mount version of the Sigma lens here, the direct competitor of course is Nikon's own AF-S 35mm f/1.4, a highly regarded lens, but also a rather expensive one. Retailing at roughly half the price of the Nikkor, Sigma now offers a more affordable option to Nikon shooters.
So, let's have a look at how the lens performs on our current FX test camera, the Nikon D3x.