I have the Canon EF 75-300mm f/4.0-5.6 III USM and I have had no problems with it. I did read what some others were saying about sigma lenses being a little soft around the edges especially when zoomed. Over here in the UK my lens retails at 189 but well worth the money, ideally I would have liked to buy the Image Stabalised version. I also use a canon 300d