|Canon EOS 400D / Digital Rebel XTi lens group test design
below from left to right are the Canon EF-S 17-55mm, EF 17-40mm, EF-S 17-85mm and EF-S 18-55mm lenses, each zoomed-out to their widest focal lengths. With a diameter of 84mm and shortest length of 111mm, the 17-55mm is by far the largest of the three lenses pictured, and at 645g, the heaviest too; this is due to the fast f2.8 aperture throughout its range, more of which later.
The 17-85mm and 18-55mm measure 78x92mm and 69x66mm, and weigh 475g and 190g respectively. The EF 17-40mm measures 84x97mm, so shares the same diameter as the EF-S 17-55mm, but is 14mm shorter. This EF lens is a little larger than the EF-S 17-85mm, but at 475g, the same weight.
Pictured below are the same lenses zoomed-in to their longest focal lengths. Here the 17-55 and 17-85mm models both extend by 26mm, although the former does so with a single barrel, while the 18-55mm extends by 9mm. The EF 17-40mm performs its zoom within the constraints of its outer barrel housing, so doesn’t physically extend. Clearly the EF-S 17-55mm remains the largest of the group.
So the first thing you’ll notice when upgrading from the EF-S 18-55mm to any of the other three lenses tested here is a considerably larger and heavier overall package. This will apply to almost any lens you upgrade to though, as the EF-S 18-55mm is compact and remarkably light. If size is an issue, you may wish to alternatively consider the Sigma 18-200mm, which at 70x78mm when zoomed-out is virtually the same diameter as the EF-S 18-55mm and only 12mm longer; see our Sigma 18-200mm review for more details.
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Build quality and focusing
The exterior design and build quality of the EF-S 17-55mm and EF-S 17-85mm are very similar, although the additional weight of the former lends it an air of greater confidence. Both are considerably superior to the build quality of EF-S 18-55mm lens, but remain below that of Canon’s L range of standard zooms, such as the EF 17-40mm.
In terms of focusing, the EF-S 17-55, EF-S 17-85 and EF 17-40mm all feature USM motors; these are much faster and quieter in operation than the EF-S 18-55mm and one of the most obvious benefits when upgrading. Unlike the 18-55mm, all three also employ internal focusing, which means the front element doesn’t rotate while focusing – great news if you’re into polarising filters.
So in terms of design and construction, you may have to accommodate a larger and heavier lens when upgrading from the EF-S 18-55mm, but you can look forward to superior build quality, along with faster, quieter and polariser-friendly focusing.
In terms of light gathering power, the EF-S 17-55mm is by far the most impressiveof the group, boasting a bright f2.8 aperture throughout its focal range. This allows it to deliver very small depth-of-fields and comfortably operate under considerably lower light levels.
To put this into perspective, when zoomed-out to wide angle the EF-S 17-55mm at f2.8 gathers twice as much light as the EF 17-40 or EF-S 17-85mm can at f4, allowing you to halve your exposure or ISO. It’s also almost twice as bright as the EF-S 18-55mm when zoomed-out to 18mm and wide open at f3.5.
With the lenses zoomed-in to their longest focal lengths, the differences become even greater. Thanks to a constant aperture of f2.8 throughout its range, the 17-55mm gathers four times more light than the 18-55mm or 17-85mm can at f5.6.
The EF 17-40mm also enjoys the benefit of a constant aperture throughout its range of f4; so while it’s slightly slower than the kit lens when zoomed-out, it’s faster when zoomed-in. Many photographers also value a constant aperture as the exposure won’t change as you vary the focal length.
Finally the EF 17-40mm has one unique advantage in this roundup: unlike the EF-S models, it can also be used on full-frame bodies like the EOS 5D. So if you upgraded to a full-frame body in the future, you could still use the lens – and enjoy its full coverage too. In contrast, Canon’s EF-S lenses cannot be used on full-frame bodies.