I have the Sigma 50/1.4 and 17-55/2.8 IS. I borrowed a Canon 50/1.4 and 50/1.8 from friends and compared corner sharpness (40D), CA and bokeh.

While I am not - by any stretch of imagination – a lens tester, I did try to eliminate as many variables as possible. I shot on tripod, used 10 sec MLU, focused via LV at 10X and used M mode. Distance was ~2m. I shot wide open, f/2, f/2.8 and f/4.

Shots were shot in RAW and converted to JPEG via DPP. Following an advice from a friend who knows a lot more than me about the digital side of life I set the sharpness to 2 in the RAW tab and 0 in the JPEG tab. That is extremely close to no sharpening at all. In my normal MO I usually set the sharpness to 5 in the RAW tab and 250 in the JPEG tab (strong AA filter in the 40D?) so you can expect to get much sharper results in "real life".

Last note: I set the FL of the 17-55 to 55mm and not 50mm as this resulted in a similar PoV. That suggests that the true FL of the 17-55 in the long end is a bit shorter than advertised. All 50mm lenses had the same PoV, at least as I could judge.

So, without further ado, here are the pictures. First, the scene of the action.

Happy shooting,
Yakim.

Wide open bokeh.

Bokeh at f/2.0.

Bokeh at f/2.8.

The 17-55 joins in. I wish I knew how to upload more pictures into one post.

Bokeh at f/4.

And the 17-55 again.

CA wide open.

And the 17-55.

Sharpness wide open.

Sharpness at f/2.

Sharpness at f/2.8.

17-55/2.8.

Sharpness at f/4.

Your 50 f1.8 seems misfocused on the last shot. It shouldn't be that soft at f2.8.

My conclusions:
Sharpness: All are sharp enough for me and I see no significant difference.
CA: The Sigma is first with no CA. The Canon 50/1.4 is a close second with little CA. The 50/1.8 is a distant third with a lot of CA.
Bokeh: The Sigma is above and beyond all others. It simply nukes them at f/1.4 and f/2 apertures. At f/2.8 and f/4 the gap narrows but it still evident.
BQ: The Sigma again comes first. Much better than the Canon 50/1.4 and light years away from the 50/1.8.

Summary: I like this Sigma. A lot. I'm especially impressed with the bokeh which is better than any lens I own (35/1.4 included). Problem is, I got an appetite for the 85/1.2 II.

Happy shooting,
Yakim.

I shot the sigma 50 1.4 on a nikon D3 and it's bokeh is very dreamy. It is an excellent lens.

deeprblue wrote:
Your 50 f1.8 seems misfocused on the last shot. It shouldn't be that soft at f2.8.

1. I did not change focus between shots.
2. As I said, I am not a lens tester and it is highly possible that some user errors crept in. I hope you find these this thread valuable despite its flaws.

Happy shooting,
Yakim.

I heard that the Sigma 50mm f/1.4 had some front (back?) focus issues at 1st. Has this been fixed in newer copies? Would be nice to have a decently sharp 50mm f/1.4 at f/1.4

Thanks for taking the time to do this comparison. I have been considering the Sigma 50 as my next purchase. The lens seems sharp with great bokeh. I have the Sigma 30 f/1.4 which is very sharp but I actually prefer the 50mm focal length. This new Sigma is very intriguing especially at 1/3 the price of the Canon 50L f/1.2.

Thanks for the tests, very interesting. It is a shame that Sigma just doesn't license the AF algorithms from Canon. They have produced lenses over the years that I would definitely have picked up ... the 50mm looks nice.

It seems to me that the images from the sigma are slightly under-exposed - does it appear that way to anyone else?

Wow the sig bok is great I am very impressed

Thanks very much for this! Gosh I miss Israeli Fanta... Haven't been to Israel in FAR too long.

While I LOVE the dreamy bokeh from the Sigma wide open, by f4 I prefer the Canon 50mm 1.4's bokeh signature since it maintains a better dream-like bokeh at that point. Interesting, though...

Am I the only one who thinks this?

In any case, the nifty fifty 1.8 clearly loses this battle, but I guess you get what you pay for.... It's still a fantastic lens for the money.

Thank you for those tests Yakim. How is Sigma's focusing when comparing with Canon?