[quot]Many dedicated APS-C lenses suffer from performance problems towards the corners of the image field but, surprisingly, the Tamron AF 17-50mm f/2.8 SP XR is one of the few lenses that which are capable to break this trend - at least within its focus plane (more on this later).
At 17mm the lens was even able to reach some of the highest measured LW/PH values ever tested in the center of the image (@ f/4). Even wide open the quality is already very good. At 24mm the quality remains basically on the same high level. At 35mm and 50mm there's a really marginal decrease in center performance whereas the border quality remains exceptionally high. [/quot]

Источник:
http://www.photozone.de/canon-eos/289-tamron-af-17-50mm-f28-sp-xr-di-ii-ld-aspherical-if-canon-test-report--review?start=1
