The 17-85mm is a member of Canon’s family of mid-range zooms, and as such the build quality is a clear step up from the lightweight plastic of the 18-55mm kit lens, if not quite up to the standards of Canon’s professional-level ‘L’ series. The lens mount is metal, and the barrel plastic; unfortunately it's not quite as solid as Canon's other mid-range zooms such as the 28-135mm F3.5-5.6 IS USM, and the plastic feels a bit thin and creaky, and deforms a little under pressure, which isn't terribly reassuring. However to its credit, and unlike the 18-55mm, the 17-85mm does have a proper manual focusing ring and distance scale. At 475g in weight, this lens is also perfectly light enough to carry around with you all day long.
On the camera
The lens feels well-balanced on both the small EOS Rebel XTi/400D and weightier EOS 40D. Controls are well-placed; the zoom ring is positioned perfectly for operation by the thumb and forefinger, with the slim manual focus ring then operated by the middle finger. When held in landscape format, only a slight shift in grip is required to reach either the IS switch, or the AF/MF switch on the side of lens barrel with the thumb, although they are somewhat less easy to find with the camera in portrait orientation. Overall, a well thought out, balanced design.
Lens body elements
The lens uses Canon's all-electronic EF-S mount. The ‘S’ designation means it is designed exclusively for APS-C digital SLRs, and the gray rubber ring on the rear prevents it from fitting on 1.3x or full-frame cameras. Owners of Canon's pre-EF-S era APS-C models (i.e. the D30, D60 or 10D) beware: this lens won't fit those cameras either.
The filter thread is 67mm. It does not rotate on autofocusing, which should please filter users.
A bayonet-type mount is provided for the petal-style EW-73B hood, but the bad news is that Canon don't supply this in the box, instead it's a pricey optional extra. Shame on Canon; I would argue that the lens hood should always be a standard accessory.
The zoom ring rotates 60 degrees anti-clockwise from wide to telephoto. The ribbed rubber grip is 20mm wide, and the zoom action smooth and precise.
The front element extends 26mm on zooming, and stays solidly positioned when set to 85mm, with no lateral play whatsoever. It can be made to wobble around a bit at shorter focal lengths, but this is unlikely to be a problem in real-life use.
The 9mm-wide focus ring rotates 90 degrees clockwise from infinity to 0.35m. It does not rotate during autofocus, and the full-time manual system allows tweaking of the focus even when the lens is set to AF. Again the action is smooth and precise; unlike the kit 18-55mm, this is a lens you can manually focus perfectly happily. Very nice.
A distance scale is provided with markings in both feet and meters, but there’s no depth-of-field markings or infra-red correction mark. The focus ring travels slightly past the infinity mark, apparently to allow for the effects of ambient temperature variations.
Two small but positive switches adorn the side of the lens barrel; the lower turns the image stabilizer on or off, and the upper switches between autofocus and manual focus. The IS switch is the larger of the two, and slightly recessed to prevent accidental movement. Both are within easy reach of your left thumb with the camera up to your eye.
Reported aperture vs focal length
Here we show the maximum and minimum apertures reported by the camera at the marked focal lengths.