|Canon EF 17-40mm f/4L Lens|
DxO Labs tested the Canon EF 17-40mm f/4L lens on a variety of camera bodies. Together with the Canon EF 70-200mm f/4L lens, these are two of the best values in 'L' lens lineup. You can read my Canon Travel and Wildlife lens recommendation, check out my equipment bag and see my works on MichaelDanielHo.com
The following is an excerpt from the DxOMark's site on the Canon EF 17-40mm f/4L lens :
Although overshadowed by its more glamorous sibling, as a moderately priced, highly portable ultra-wide zoom, the EF 17-40mm f/4L USM is a hugely popular model. Read on to find out how well it performs in our labs.
Introduced in 2003 the EF 17-40 f/4L USM was one of the first of the lightweight pro-level L-series zooms from the firm adopting a constant f4 aperture. Not only does that make the lens relatively small and more portable compared with the f2.8 varients, but it also helps keep it moderately priced. This full-frame lens is also popular with users when mounted on APS-C cameras where it’s the equivalent to a 27-64mm. Like other L-series lenses from the company, the EF 17-40mm f/4L has a high grade optical construction consisting of three aspherical lens elements and even adopts a Super-UD glass element, an expensive glass type usually resevered for more esoteric lenses in the range. The 12-element 9-group construction allows a closer than usual minimum focusing distance of 11.02” (0.28m). It weighes 1.05 lb (475g) and measures 3.81” (96.8mm) in length, and is available now for $839