Canon EF-S 17-55mm f/2.8 IS USM - £770
This is the nearest thing to a fully professional, L-series lens in Canon's stable, even if Canon never applies the 'Luxury' tag to EF-S lenses. The zoom range is quite modest and image stabilisation is of an older, 3-stop generation, but image quality is sublime.
The build feels particularly rugged and hard-wearing, and the upsized manual focus ring (compared with the EF-S 15-85mm) makes for silky smooth manual override of autofocus. This ability is thanks to the advanced, ring-type autofocus system featured in all of the Canon lenses on test.
A major attraction of this lens over the EF-S 15-85mm is its f/2.8 maximum aperture, which remains constant throughout the zoom range. This enables you to keep shutter speeds up in gloomy conditions, as well as delivering a really tight depth of field, especially at the long end of the zoom range.
The bokeh (quality of defocused areas of the image) is very pleasing, making the lens ideal for portraiture.
Distortions, colour fringing and vignetting are well controlled, while sharpness and contrast are fabulous. It's the most expensive APS-C lens in the group, but well worth the money.