In the last decade or so, Sigma has grown from one of the better third-party lens manufacturers to one of the best lens manufacturers, period. Once a second-tier option that you’d only settle for if you couldn’t afford the real deal, Sigma’s recent offerings, especially their Art lineup, are as good or better than their first-party equivalents, often for significantly less money. The best example of their recent expertise is the Sigma 50mm f/1.4 Art, which is available in a Canon mount. In my opinion, it’s the best 50mm prime for most portrait photographers, regardless of budget.
Compared to the Canon 50mm f/1.2L, the Sigma is sharper, has a shorter minimum focus distance, displays less chromatic aberration, and has one more aperture blade. Sure, none of these individual characteristics are going to make a huge difference in your portrait photographs, but the Sigma is also significantly cheaper.
As of right now, depending on where you buy, you should be able to find a new Canon 50mm f/1.2L for around $1,400 retail, while a Sigma 50mm f/1.4 Art will only cost you about $950. That’s not nothing. The Canon, of course, is a little faster, but for most photographers that small amount of extra light won’t make much of a difference.
If you don’t need the absolute performance of the Otus 55mm or the extra bit of wide-open exposure from the Canon 50mm f/1.2L—which, if we’re being honest with ourselves, most of us don’t—then this is the lens for you. Just about every portrait photographer should own a 50mm prime, in my opinion, and, for my money, the Sigma 50mm f/1.4 Art might be the best buy in still camera lenses today.