Canon EF 17-40mm 1:4 L USM

The Canon EF 17-40mm f/4 USM L showed a very good to excellent performance in the lab as well as during the field tests. The lens exhibited very little vignetting and excellent resolution figures. On the downsode the level of distortions could haven been a little better at the wide-angle setting. Typical for most wide-angle zooms chromatic aberrations can be visible but the problem remains comparatively low. The quality of the construction is next to perfect.

The Canon EF 17-40mm f/4 USM L is a very good performer without a significant weakness. It's generally very sharp and contrasty across the image field. Vignetting is very well controlled - at least when using it on an APS-C DSLR. You may spot some barrel distortion when using the lens at 17mm but it's not all that bad. Typical for most wide-angle zooms chromatic aberrations can be visible but the problem remains comparatively low. The quality of the construction is next to perfect. Looking a bit beyond the APS-C scope it is worth to mention that the lens didn't perform quite as well during our corresponding full format test so the straight-forward idea of buying it now for an APS-C DSLR and using it at a later stage on a full format DSLR may not be as desirable as it may appear. It also faces stiff competition from the Canon EF-S 17-55mm f/2.8 USM IS which is both faster and slightly superior. However, from a price/performance perspective it is still an attractive lens for APS-C users.