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Lens review

Canon EF 17-40 mm f/4.0L USM

22 September 2007
Robert Olech

3. Build quality

The lens was designed to meet the needs of reporters working in the most difficult climates. The high quality build can be noticed at first glance. The designers used a die-cast magnesium alloy in the lens’s constructions and the lens’s size does not change while zooming, thus allowing the lens to stay clean (since no dirt can get inside). The build is complemented by two wide and very comfortable rings; one for the focal length changing and the second one for manual focusing.

Canon EF 17-40 mm f/4.0L USM - Build quality

Canon EF 17-40 mm f/4.0L USM - Build quality


If we compare the Canon EF 17-40 mm with other verifocal lenses like the Tamron 17-50 mm or Sigma 18-50 and 17-70 mm, the results are not great, although the Canon has the weakest aperture. But when taking into the consideration the fact that the Canon was designed to achieve the ultra-wide field of view the large size can be excused. It is clearly seen in the Canon EF-S 10-22 mm. Both lenses (the 10-22 mm and 17-40 mm) seem to be very similar. They are both designed to achieve wide field of view with the first one using the APS-C detector and the second one the full frame. No wonder then that their construction, size and the way they look are very similar, as can be observed in the pictures below.

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Canon EF 17-40 mm f/4.0L USM - Build quality


In the middle of the Canon’s solid build we can find 12 lenses set up into 9 groups. It is worth adding that one of the elements was made of SUD low dispersion glass and three others are aspherical lenses. The lens includes a seven-blade diaphragm.

Canon EF 17-40 mm f/4.0L USM - Build quality

The whole construction of the lens allows the user to obtain high quality pictures from a distance of just 28 centimeters. Unfortunately, the size requires the usage of big filters, which, in Canon’s 17-40 mm case, needs to be a 77 mm filter. Since it would be a faux paux to use any filter with the L-grade lens, this pleasure would cost us a lot. As an example for the B+W UV filter of this size we would have to pay about 80$. Polarized and field filters would be even more expensive…