Summary: Having read multiple reviews from every web site I could find on the most bang for your buck 50mm for canon, I made the leap of faith and purchased this lens at the local shop. This was not one that had been sitting around, because they had just gotten in a new shipment. I had read about the focus problems with this lens when it first shipped, but I was under the impression from most reviewers that this issue had been resolved. In my case, this was not true.
Summary: I tried four copies; three were bad, one was awful. This lens has been very favorably reviewed, and I find their 50 f1.4 to be magnificent, so I took a chance. The only thing I can think, based on what I saw in the files, is that in each case, one or more of the elements was out of alignment, because they didn't produce a normally focused image at any focus distance.
Excerpt: Front Focuses on anything within 5 feet. Back focuses on anything beyond 10 feet. Inconsistant in the mid range. Looking at reviews in forums this is a pretty normal thing with sigmas. When they are built well they are really good, when not they are terrible. Trouble is you never know which you will receive. Are you feeling lucky?
Summary: I was 0 for 2 with the Sigma 30mm bought at Amazon. Got the first one, focus was terrible. I mean the only thing I could get in focus on my xti was a shot outside at f/8 and infinity. I tried to focus on my birdfeeder at 30 feet and was really blurry (with plenty of shutter speed). Inside was a little better but completely unacceptable compared to my 50mm f/1.8. Sent it back and got another from Amazon. A little better inside.
Summary: I had high hopes for this lens. My 50mm f/1.8 nikkor is a great lens, but sometimes I just don't have enough room to get everything in the shot. So I purchased the Sigma 30mm f/1.4, also being excited about the extra stop because I often take photos in low-light situations. I was aware that there were some defective copies of this lens, but thought that maybe I would get lucky. Alas, no such luck.
Summary: I have a canon 60d and was looking for a lens equivalent to 50mm on my cropped sensor. I spent hours/days reviewing what lens to buy. I knew I was taking a gample going for a Sigma lens as it was clear after reading copious amount of reviews that you are playing Russion Roulette in trying to get a good copy. I decided to take the gamble, as it seems when you get a good one, it's apprently extremely good (I didn't acutally buy it from amazon). However, I got a duff one.
Summary: I held off for quite some time before getting this lens, put off by reviews mentioning focusing issues. in the end i couldn't resist. I really wanted to love it, i went through 4 copies to get a copy which focussed spot on with my body (550d). However even though focussing charts were spot on, i found the lens missed focus far too often, especially in lower light which is exactly when you would want to be reaching for this lens.
Summary: Lange Zeit habe ich an meine Canon 60D nur das Canon 15 - 85mm Objektiv gelassen. Super, Empfehlung. Trifft eigentlich immer, sofern ich es nicht selbst verpfusche. Dann das Canon 85mm 1,8 USM. Als Porträt-Linse einfach klasse und das zu dem Preis. Allerdings muß man für Innenaufnahmen dann schon Platz haben und das geht ja nicht immer. Also Festbrennweite so um die 30mm.