Bests & Worsts Reviews from Amazon

Prior to ordering this lens, I probably spent more time reading owner reviews than I have for any other lens I own. At the time of my order, I think Amazon listed some 85 customer reviews of this lens. It was hard to arrive at a conclusion. Image quality was generally not a point to be disputed. In fact the majority of owners had nothing but good to say about this lens. But, some complained of issues related to a failure to auto-focus when shooting at or near wide open aperture settings especially shooting close-ups in subdued light. I wondered why so many were pleased while others had focus problems. And, while what I have to say should not be construed to be conclusive (perhaps there are some bad copies that slipped through the QC department at Sigma)I wanted to share with others my experience with this lens and what I did to fix my focus problem. Obviously, I purchased one..... A lens like this is generally purchased with one or both of the following in mind. Either for portrait work or for low light shots. Therefore, it is near essential that the auto-focus be spot on. No auto-focus lens is perfect in that it is impossible to be on the dot 100% of the time, but if the majority of your shots are not keepers, there is a problem to be reckoned with. You could rely on manual focus (I do sometimes where a shot is critical, I won't trust auto-focus alone)but you paid for auto-focus and you obviously laid out the cash for a reason. When my lens arrived, I went to work shooting test shots to see how auto-focus worked at these wide open settings. Sure enough, many shots were blurred. I tried manual focus, no problem, most of the shots were sharp. I sat down and thought about it for a while and it occurred to me that the camera was set to use multiple point auto-focus. I thought some more and realized that I had not really paid attention to what point/points were locking in. I reset the camera to a single (the center) focus point. At wide open (f/1.4) I shot close-ups of my wife (close enough that her face filled the frame) placing the single center point on her forehead. Wahlah.......perfect focus. Multiple test shots produced like results. I am wondering if others have made the same oversight as I did. With focus being so critical at these settings and distances, it is imperative that as much margin for error as possible be removed. I knew that when shooting with apertures wider that f/2.8, a single focus point should be used. I am wondering if others may have made this same oversight??? I can't recall reading any remarks concerning this. In any event, if you have a Sigma 50mm f/1.4 and you have had focus problems, give it a try if you haven't tried it already. I must say that I am pleased with this lens now that I have resolved the focus problem. It is sharp as a tack and is quickly becoming one of my favorites. It is a great value when compared to it's competitors besides being a beautiful lens to look at with all that big glass.......