Hi, and welcome to the TDP forums!


Quote Originally Posted by tk303
I tested them with my canon T2i on a tripod at same focal lengths and same apertures.

Sorry, but are you certain? The framing is different (the 17-55mm is shifted to the right, but even compensating for that, the 17-55mm framing is slightly tighter - that may be due to imprecision on the zoom ring markings - check the EXIF data). Also, the OOF area appears blurrier with the 17-55mm, suggesting the aperture is wider (again, check the EXIF - if the same, the 17-55mm is delivering more background blur).


Image quality is difficult to judge in a 550 pixel-wide forum image - a common convention is to post 100% crops from center (assuming that's where you're focusing) and corner (framed identically so we're looking at the same part of the image). Also, to check corner performance, you really want a subject that's flat, so the corners are in the plane of focus (or focus on a corner with 10x live view).


--John