At the moment I’m searching for a replacement lens for my Canon EF-S 18-55mm 1:3.5-5.6. I’m now taking a closer look at the Sigma 18-50mm F2.8 EX Asp. IF (around 400 EUR) and the Tamron SP AF 17-50mm F/2.8 XR Di II LD ASL IF (around 380 EUR). I’ll possibly try to test both at a local photo dealer to find out the better one for me. Anyone with experiences concerning these lenses? I’ve read this test and it draws a quite nice picture of the Sigma. But no final decision done yet.