side-by-side comparison with Ls

First side-by-side comparisons between the EF-S 17-55mm f/2.8 IS USM and the EF 24-70mm f/2.8L USM and EF 16-35mm f/2.8L USM:

http://www.fredmiranda.com/forum/topic/396162/0

The background is that the 24-70 is only marginally cheaper than the 17-55, while the 16-35 is marginally more expensive, but both L lenses fall way short in any feature comparison. So if the EF-S 17-55 matches up to those lenses in image quality, the only reason for somebody with an EF-S-compatible camera to choose those other lenses is better build quality. Most everything else is greatly in favor of the 17-55.

Sure enough, in both comparisons (crops from the corners of the frame), the 17-55 is clearly sharper than the 24-70, and makes the 16-35 look positively embarrassing.

The 17-55 has slightly more contrast than the 24-70, and significantly more than the 16-35.

Both L lenses have more saturated colors than the 17-55, even after compensating for the increased light fall-off in the 17-55 (which makes corner crops darker).

Given a choice between sharpness and saturation, I'll take sharpness any day. Boosted saturation in post-processing is much less noticeable than fake sharpness.

That pretty much closes the book for me: not only is the new 17-55 the best value among Canon's premium zooms, the evidence is mounting that it is the absolute best Canon lens below 50mm, regardless of price and focal length range. The only question left for me is whether or not one of the much cheaper, non-IS, third-party alternatives is a better value.