Originally posted by GrimWolf I think i'll give the lens one more go on friday as there are ducks, swans and other birds locally. I'll try out different speeds and tripod etc. If it comes out the same, I'll return the lens and look at another model.
Why do you need to wait if you can test the lens focusing on anything around? Speed was so low, but acceptable in many cases if your hands are steady. Seems more like out of focus image to me. This lens (and similar Sigmas 70-300mm ) tends to hunt especially in not sufficient light (even shade or clouds in bright day). I never use ISO number lower than 400. Usually 400-800 for this lens in any light to catch flying birds as well.
I suggest you practice more with your Sigma. AF is a pain often, but it's manageable if nothing is wrong with the lens of course.