I have more lenses than I need (16-35mm f2.8L II, 24mm f1.4L II, 24-70mm f2.8L II, 24-105mm f4.0L IS, 50mm 1.2L, 85mm 1.2L II, 100mm f2.8L Macro IS, 70-200mm f2.8L IS II and 400mm f2.8L IS II) and I am willing to pay the price to get the best (even though Canonīs prices are getting more and more unacceptable). So when I recommend this Sigma so highly, it is because it is as good as it is compared to lenses of any price.
Despite that I have many alternatives, I must admit that this lens has been stuck on my 5DIII since I got it (the 24-70mm f2.8L II and the 85mm f1.2L II alternates on my 1DX. They are both gorgeous lenses). I have always liked primes, for two reasons. First you get the better aperture for both low light capability and shallow depth of field and you get the extra challenge of moving yourself instead of just zooming. I use primes more than zooms. The 35mm focal length is in my view very useful and when you combine it with f1.4, it is really good. In general I find the Canon L-lenses better than the Sigmas, Tamrons and other independent lens manufacturers in two areas. One is autofocus, both speed and noise and the other is optical quality. But in the case of the Sigma 35mm f1.4, it is not the case.
I have not measured AF speed exactly, but it is fast enough to be a non-issue for me. The guy in the video (see the link I posted yesterday), claimed it was from 0 to 1/10 of a second slower than the Canon 35mm f1.4L from infinity to close-up. Noise level is as low as the USM on a Canon lens.
I now have several hundred images verified and from a pure image quality perspective, provided I havenīt been overly lucky with the quality of my sample, the quality is outstanding. Sharpness, bokeh, color, vignetting and flare performance are all simply excellent. The sharpness in the corners at f1.4 is bit less impressive, but it is still very good. AF accuracy is also both consistent and precise. I have read somewhere that Sigma has been less consistent on AF in the past. I only know what this lens has done it the first weeks I have had it. The fun part of having a 1.4 aperture is that you also get fairly shallow depth of field also on a 35mm and you can use that to isolate your objects and get some really cool effects.
I also really like the mechanical feel of this lens. It looks good, feels rock solid, it is good in my hand, the focus ring is wide and tight and the balance with the 5DIII body is great.
If a 35mm f1.4 is high on your wish list, regardless of price, this is it. Take the $500 you save from skipping the Canon and buy your partner something nice for Christmas. Or you can set them aside for the other lenses I hope Sigma will produce with similar quality.