To illustrate the range in practice we mounted an EOS 400D / XTi on a tripod and photographed the same scene with the EF-S 10-22mm at its shortest and longest focal lengths, then repeated the process a few moments later with the standard EF-S 18-55mm kit lens for comparison.

Canon EF-S 10-22mm f/3.5-4.5 USM
10-22mm at 10mm, f8 (16mm equivalent)		10-22mm at 22mm, f8 (35mm equivalent)

Above are the shots taken with the EF-S 10-22mm and below are those taken with the EF-S 18-55mm. Most obviously the EF-S 10-22mm captures an enormous field of view at 10mm, compared to the kit lens at its widest position, and there’s also some handy overlap at the longer end, with the EF-S 10-22mm zooming-in to a semi-wide focal length that could actually see it being used as a walk-around lens – albeit for wide-angle fanatics.

Canon EF-S 18-55mm f/3.5-5.6
18-55mm at 18mm, f8 (29mm equivalent)		18-55mm at 55mm, f8 (88mm equivalent)

So what would you use such a wide angle lens for? Well as we’ll show in the Gallery on the next page, zooming-out to an equivalent focal length of 16mm allows you to capture massive views even at close range, which can be handy if you literally can’t step back any further. It’s equally useful for squeezing in large buildings at close range, or making interiors look bigger than they really are. Suffice it to say large group shots are never a problem.