Digital Photography Review (DPR), one of the web's most-trusted resources for all things digital photography, has just posted an in-depth review of the new Sigma 50 f1.4 Art lens, which the company bills as being a direct rival to the $4000+ Zeiss Otus.
So, does the Sigma live up to its billing? Short answer: yes.
Optically, the lens is really good. In terms of sharpness, the lens is good right from the get-go at f1.4. On sub frame, f1.4 is sharp corner to corner and only exhibits a little softness in the corners on FF. Remedy/ Stop down to f2 to reduce the problem and f2.8 to eliminate it. From then on, the lens remains extremely sharp, only losing a little sharpness due to the diffraction limit at f11 and a bit more after that at minimum aperture, f16. As for chromatic aberration and distortion, both are very well controlled and should not present any real problems in real-life shooting. Vignetting? Being a f1.4 optic, it's there but is controlled to under a stop and a half of falloff on full frame, a truly impressive feat for such a lens.
Mechanically, the lens is built in line with the other global vision models, as in like the proverbial tank. For materials, the lens uses a metal mount and a barrel of Sigma's patented Thermally Stable Composite (TSC). The lens features a wide 1.5 inch, rubberized focus ring. Additionally, it has a distance window and a 9-bladed, rounded aperture for ultra smooth bokeh.
As for focus, AF is via Sigma's Hyspersonic Motor (HSM) technology, which results in fast, virtually silent AF. Additionally, features full time manual focus capability. Needless to say, there's no spinning focus ring when in AF mode. DPR reports AF as being very accurate in traditional focus mode, too. As for live view, the Canon 70D, with its dual pixel AF, stands out among the crowd, though this is more a function of the camera than the lens, though.
Overall conclusion: praise at the highest level, with DPR reviewers even going so far as to say that this Sigma is the best 50mm AF lens they've ever tested.
Want one? Well, it sells for $949, provided you can find one!