"I second John's recommendation of the Sigma 50 f1.4 Art, it is a very impressive lens."
The Sigma 50mm f1.4 Art may be the sharpest lens made. It is certainly near or on top of the list. Only giving way to the Sigma 35mm f1.4 Art, perhaps.
I had the Sigma Art and sold it for the fantastic and unique ef 50mm f1.2L. There are two things that you need to know about it. One, there is nothing like f1.2 at 50mm. And, if you need f1.2 it has it and the Siggy doesn't! No other 50mil lens I know of has f1.2. Reasonable lens that is. Second, this is not a lens you will pick up and run with. It takes some time to learn its idiosyncrasies. A fast shallow f1.2 takes some time for best results.
Is it as sharp as the Sigma Art 50mil? No, but sharpness is only one spec of any lens has. You must take the entire package in to account when you buy lenses. Some people, perhaps even John and Rodger, get caught up on the sharpness of lens and fail to see the rest. Don't get me wrong the 50mm f1.2L is plenty sharp.
Personally I am not a fan of 50mm. Basically because it is a more difficult FL to use unless you have a specific purpose for it. At one time the 50mm was king. All 35mm film cameras came with it so I have extensive experience with 50mm. However, that old question, what would be the last lens you would ever sell or get rid of? The ef 50mm f1.2L would certainly be a top candidate onmy list. I love it and I also love its big brother the ef 85mm f1.2l. Did I say there is nothing like f1.2?
Yes, I did sell my Sigma 85mm Art f1.4, too! 
@ebiggs1 wrote:"I second John's recommendation of the Sigma 50 f1.4 Art, it is a very impressive lens."
The Sigma 50mm f1.4 Art may be the sharpest lens made. It is certainly near or on top of the list. Only giving way to the Sigma 35mm f1.4 Art, perhaps.
I had the Sigma Art and sold it for the fantastic and unique ef 50mm f1.2L. There are two things that you need to know about it. One, there is nothing like f1.2 at 50mm. And, if you need f1.2 it has it and the Siggy doesn't! No other 50mil lens I know of has f1.2. Reasonable lens that is. Second, this is not a lens you will pick up and run with. It takes some time to learn its idiosyncrasies. A fast shallow f1.2 takes some time for best results.
Is it as sharp as the Sigma Art 50mil? No, but sharpness is only one spec of any lens has. You must take the entire package in to account when you buy lenses. Some people, perhaps even John and Rodger, get caught up on the sharpness of lens and fail to see the rest. Don't get me wrong the 50mm f1.2L is plenty sharp.
Personally I am not a fan of 50mm. Basically because it is a more difficult FL to use unless you have a specific purpose for it. At one time the 50mm was king. All 35mm film cameras came with it so I have extensive experience with 50mm. However, that old question, what would be the last lens you would ever sell or get rid of? The ef 50mm f1.2L would certainly be a top candidate onmy list. I love it and I also love its big brother the ef 85mm f1.2l. Did I say there is nothing like f1.2?
Yes, I did sell my Sigma 85mm Art f1.4, too!
Actually, I have the Canon 50mm f/1.2 and do not have the Sigma f/1.4. Everything you said about the 1.2 is why I recommend the 1.4 for the OP. It is a very special lens and not one I would recommend for someone who just wants two very good lenses.
"It is a very special lens and not one I would recommend for someone who just wants two very good lenses."
And neither do I, that is why I added the caveat. It is a lens that takes some time to learn. Some will never master it. The fact remains if you don't use the f1.2 aperture, the big 50mil isn't really any different than any other 50mm. Perhaps a bit slower to AF but certainly adequate. It is heavier, too, but you don't get that big piece of glass without weight.
When comparing the f1.2 to the f1.4 50 mil's, which is not a stellar performer, BTW, the ef 50mm f1.2L wins every time in my book.
You'er not one of those that struggle to use the ef 50mm f1.2L are you, John? 
One note further if the 50mm f1.2L gives you trouble, don't even consider the ef 85 mm f1.2L. It doubles the quirks easily. If you need f1.2, you need f1.2. These two lenses are unique.
