I just got new lens for my camera. It should replace two of my lens Sigma 20 1.8 EX DG Aspherical RF and Tamron SP AF28-75/2.8 XR Di LD Aspherical. The Canon EF 17-40mm f/4 USM L has a very good to excellent performance. The lens exhibits very little vignetting and excellent resolution figures. The construction quality is next to perfect. All-in-all probably the best standard zoom for APS-C Canon EOS DSLRs at the moment. I will put it into test soon during my trip.