photozone comparisons

If we agree with Klaus Schroiff that PhotoZone's MTF50 measurements are indicative of perceived sharpness, there are a number of interesting comparisons between the EF-S 17-55mm f/2.8 IS and other premium Canon lenses.

As mentioned before, the 17-55 is marginally sharper in the corners stopped down at 35mm than the comparably-priced EF 35mm f/1.4L.

It is also sharper in the corners (all these lenses exceed the limits of current Canon sensors in the center) than the comparably-priced EF 24 f/1.4L, all the way from f/2.8 to the diffraction limit.

It is sharper at both 17mm and 24mm than the comparably-priced EF 24-105mm f/4L at 24mm, at all comparable apertures. The 17-55 is sharper at f/2.8 than the 24-105 is at f/4, and at f/4, the 17-55 is sharper than the 24-105 at any aperture.

The 17-55 is sharper at 35mm f/4 than the 24-105 is at 40mm f/4, but at smaller apertures, the 17-55's corner performance falls behind that of the 24-105.

At 55mm, the 17-55 is sharper than the 24-105 at 70mm, with both lenses at the same apertures.

The 17-55 has less chromatic aberration, but more vignetting and distortion than any of the three lenses mentioned above (actually, it has less distortion at 24mm than the EF 24mm f/1.4L).

Note that all the EF lenses are full-frame, and we are only seeing their "sweet spot".