Ok, went on a shoot yesterday (in more ways than one...!) and took around 80 images of people shooting clay pigeons. Camera is a 350d and the lens for the day was a Sigma 24-70 EX DG jobbie. It's about 4 months old and I've not usually had any problems with it. Most of the shots came out fine - here's a 100% crop of a trap at f5 and 70mm: Not a problem. The problem was with all of my macro shots of the day. I took all of these at 70mm and f2.8, and using autofocus. Here's an example of a macro at 100%: Bad. Very bad. All the macro ones at 70mm and 2.8 were like this. I don't think it's camera shake, as that one is at (from memory) 1/400. Just to prove that it's possible only macro shots - here's a far-away shot at f2.8 and 70mm. I know it's ISO800, but it's not particularly blurry, and in low light and hand-held, that could just be shake. Crude, but maybe proves that point: So then I tried a macro. It's ISO 1600, but came out not too bad, which proves the lens isn't that bad when it does macro stuff: Therefore, there's a number of posibilities: 1) The cold/light drizzle made the lens not focus properly on macros. 2) For every single shot, I focussed, then moved. 3) There's a temperamental fault with the lens 4) I'm insane. Any thoughts as to which of these it could be?