The Canon EF-S 17–85mm f/4–5.6 IS USM is a standard zoom lens for Canon digital single-lens reflex cameras with an EF-S lens mount and image stabilization.[1][2][3] The EF-S designation means it can only be used on EOS cameras with an APS-C sensor released after 2003. The field of view has a 35 mm equivalent focal length of 27.2–136mm, and it is roughly equivalent to the Canon EF 28-135mm lens on a 35mm film SLR. Despite the word "macro" being present on the lens body (as visible in the infobox image), this lens is not capable of true 1:1 macro photography.

The 17–85mm was bundled as a kit lens with the EOS 30D, EOS 40D, EOS 50D and EOS 60D. It was also packaged with the EOS 400D (known as the Digital Rebel XTi in North America) as an alternate to the EF-S 18–55mm (typically labeled as the "400D enthusiast's kit").

The Canon 17-85 IS is sharpest at the telephoto end, but doesn't give up much when shooting at shorter focal lengths either. At wide angle, sharpness doesn't change much at all, from wide open down to about f/11, a somewhat unusual characteristic. At other focal lengths, the first full stop down from wide open brings the most significant increase in sharpness, except in the vicinity of 60mm, where we found that it took two stops down (to f/11) to get the sharpest images.

Chromatic aberration is quite good from roughly 60-85mm, but heading the other direction, it rises a bit at 35mm, and takes a real leap at 17mm. - Aberration at maximum wide angle is well on the high side of average. Vignetting or light falloff in the corners of the frame is on the high side of average at 17mm, at about 0.8 EV, but that's still somewhat less than the roughly 1.05 EV of the competing Nikon optic. Falloff at wide angle decreases to 0.5 EV when the aperture is closed down a stop, to f/5.6, and at longer focal lengths never exceeds 0.3 EV. The 17-85 struggles most with geometric distortion, starting out quite high at 17mm, with about 1.2% barrel distortion, then dropping rapidly to about 0.5% pincushion at 35mm, and finally tapering down to about 0.4% pincushion at 85mm.

Overall, this lens is a nice performer, and the IS is a real boon for hand-held photography in uncertain lighting. As such, it deserves strong consideration for your main lens, if you're buying a Rebel XT or EOS-20D, both of which are offered in bundles with this optic. If you have one of the Rebels, this lens might be a nice upgrade for you, giving you a bit more range at the telephoto end and Canon's very capable Image Stabilization at an affordable price.