[Canon EF] I, too, have read the reviews and seen the hype so I decided to give this lens a try knowing B&H would take it back if I wasn't sold. After using it for a week, I've fallen in love with it. I guess I'm keeping it! This lens is tack sharp wide open and I love the creamy background. It stays at f/1.4 (otherwise, why have it?) Yes, it is heavy and quite obvious on your camera unlike most 50s but the images more than make up for the size.

[APS-C] I used the earlier version, and thought is was an above average lens for the Pentax. Only one of my Pentaxes is full-frame, so I don't shy away from the APS format lenses. This lens is one of my best Pentax mount lenses. So far the results have been extremely sharp and high in contrast. I read that Sigma was cutting back on lenses for Pentax mount, so I had to give this one a try and I'm glad I did.

[Autofocus] This is a great lens at a fair price. I've only had it about a month but I'm glad I bought it. It's a great focal length and come on, it's a 1.4!
I've been a long time fan of Sigma lenses. For me, Canon lenses have been hit or miss but my Sigmas never disappoint.

Sure, I agree with reviews that say, 'hey stop it down for better sharpness' or there's some distortion at 1.4 or whatever.

Still a total keeper of a lens.

[62 mm (Front)] Best lens I've ever keep in my hands. I'm using Sigma 150/2.8 macro for more then 10 years. This lens is a new step both for me and for Sigma:) Even a little bit sharper than 150/2.8 (big surprise for me). High microcontrast at f=1.4-2.0. Very nice colours rendering, deep and harmonical. Surprisingly good at Canon XTi - perfect portrait lens. Very good at Canon 5D. Very good in low light. A little bit heavy. With Canon XTi system is not balanced.

[62 mm (Front)] Best lens I've ever keep in my hands. I'm using Sigma 150/2.8 macro for more then 10 years. This lens is a new step both for me and for Sigma:) Even a little bit sharper than 150/2.8 (big surprise for me). High microcontrast at f=1.4-2.0. Very nice colours rendering, deep and harmonical. Surprisingly good at Canon XTi - perfect portrait lens. Very good at Canon 5D. Very good in low light. A little bit heavy. With Canon XTi system is not balanced.

[Autofocus] I'm a professional wedding photographer, I shoot over 50 weddings a year. I've always been skeptical about anything less than Nikon glass. With all the articles and reviews on the Sigma Art series lens. I figured why not try it, if it doesn't live up to what's written I'll send it back.I own a Nikon 58mm 1.4 lens, this was my benchmark. Can I use the 50 instead of stealing my wife's 58mm all the time. After using it for now a month I can tell you without a doubt this is an amazing lens. It's as good if not better than Nikon's 58 1.4. For half the price, this is a no brainer lens. The only, and the only downside is the weight. It's much heavier than the 58mm. The 58's weight is amazing, light but still professional feeling. The sigma is heavy, but feels rock solid.

[Autofocus] I'm a professional wedding photographer, I shoot over 50 weddings a year. I've always been skeptical about anything less than Nikon glass. With all the articles and reviews on the Sigma Art series lens. I figured why not try it, if it doesn't live up to what's written I'll send it back.I own a Nikon 58mm 1.4 lens, this was my benchmark. Can I use the 50 instead of stealing my wife's 58mm all the time. After using it for now a month I can tell you without a doubt this is an amazing lens. It's as good if not better than Nikon's 58 1.4. For half the price, this is a no brainer lens. The only, and the only downside is the weight. It's much heavier than the 58mm. The 58's weight is amazing, light but still professional feeling. The sigma is heavy, but feels rock solid.

[1.56 lb] Great lens in terms of fast auto focus and super sharp image. More difficult to focus at 1.4 then my Nikon 50mm 1.4 because SO much bokeh in this lens. Significant less vignette at 1.4 then my Nikon lens and incredibly sharp at 2.2 and 2.8. Use this for food photography where the sharpness is great and also as a portrait lens for new born pictures and pictures of my kids. Biggest negative is that the lens is very heavy compared to my Nikon 50 mm 1.4. But it is a great lens and seems to be built well.

[1.56 lb] Great lens in terms of fast auto focus and super sharp image. More difficult to focus at 1.4 then my Nikon 50mm 1.4 because SO much bokeh in this lens. Significant less vignette at 1.4 then my Nikon lens and incredibly sharp at 2.2 and 2.8. Use this for food photography where the sharpness is great and also as a portrait lens for new born pictures and pictures of my kids. Biggest negative is that the lens is very heavy compared to my Nikon 50 mm 1.4. But it is a great lens and seems to be built well.

[f/1.4] This lens is great for all around photography on an APS-C camera. A circular polarizing filter goes a long way for this lens in bright environments.