I've bought a used Sigma 70-210 1:4-5.6 Multi Coated lens from a guy at ebay, to replace an exactly the same lens that had broken down. It works very well. Zoom is quick and there is nothing to complain about apart from a noise that I didn't have on my first lens. It sounds like something could be wrong. The guy I bought it from wrote this in the description: "Not sure if its a characteristic of the lens but the focus is not silent." I know it's not a silent lens from the beginning, but this is way out sounding to much. Please :hail: listen and say what you think. I have recorded a soundfile of my camera focusing: I'ts just a 300K file. Link to a sound file recorded of my lens making strange sounds. By the way. My camera is an Canon EOS 650.