The build quality of Nikon's 50mm 1.8 offering is so much better than Canons. It has a metal mount, a nice dampened rubber focus ring, a distance scale. There is really no excuse for the flimsy plastic lens that Canon offers, they have to do better than this. I know that optically it's great, but I've gone through three of them in 5 years because they have all lost their ability to focus accurately. I've done extensive testing, and they all begin to back focus after about ten feet. They have all started off with nice accurate focusing. It's not at all abuse, I baby my lenses. I believe it's simply the extremely cheap plastic body and gearing of the focus mechanism. Some have said that Canon keeps this lens so shoddy because they feel like no one would buy their 50mm 1.4 if the build on the 1.8 was good. To this I say, it works for Nikon. They have a high quality 1.4 and 1.8 and sell both. I know I can get an old mark I 1.8 on eBay, but I'd rather canon create a new, high quality 50mm 1.8 prime. I would gladly spend $200 or $225 if they had a lens with a build quality on par with Nikon's. Thank you.