My question is clear, sigma has a cheaper 50mm 1.4, that is newer, and made for digital camera, with all it's coatings, and apparently it has a special digital focusing system. But, then there is the 1.2 l, it has about half a stop of luminosity more, which I don't know what difference that makes, and it's an "l" lens.
Please keep in mind that I'm asking which is better in total and in different ways.
This is to fill a gap in my range, (16-35 and 70-200 2.8 is ii), so I'm looking for one that won't fail me
The Sigma is just 1 year newer than the Canon, so don't use that as consideration between the two. Also, "Made for Digital" doesn't really mean much, except that it has modern coatings. All new lenses have similar types of coatings though.
Another thing, the Canon is 1/3 stop faster, not 1/2, so again, not much between them.
I own the Sigma and have used the 50L and I have to say there isn't really much between them in terms of image quality: both are excellent, especially at wide apertures. The Sigma has less CA in my opinion, but is maybe a touch softer; however, the reduced CA is a nice thing to have. Both have good contrast wide open and amazing from f/1.8. Both have nice bokeh, but I might give the nod to the Siggy here (this is very subjective, of course). Neither lens will disappoint; they are tops in terms of wide aperture performance in the 50mm class.
However, the Canon has much better build quality and the AF is definitely better too. The Canon seems to suffer from spherical aberations more than the Sigma, so focusing can be off if you use the center point from f/2-4, but it's AF is more consistent. My Sigma's AF is working well after MA, but only at the expense of longer focus distances at wide apertures (if I focus on something 25+ feet away at f/1.4-2.8, it is OOF, but at normal distances, it's perfect).
I'd say that if the difference in price doesn't bother you, get the Canon. If you want similar image quality and don't mind the more pedestrian AF performance and build quality, the Siggy is a great option. I love mine and am no longer drooling over the 50L. If Sigma built a 24/1.4 as well as their 50, I would have saved a lot by not buying the 24L.