A new and affordable L-series ultra-wide-angle zoom lens that’s ideal for both film and digital SLRs. Superior optics are assured by the use of three Aspherical lens elements, in addition to a Super UD (Ultra-low Dispersion) glass element. Optical coatings are optimized for use with digital cameras. This lens focuses as close as 11 inches (0.28m), and offers both Canon’s full-time manual focus and a powerful ring-type USM for fast and silent AF. It has a constant f/4 maximum aperture, and offers the choice of screw-in 77mm filters or a holder in the rear of the lens for up to three gel filters. Finally, it offers weather-resistant construction similar to other high-end L-series lenses.

Read more at Canon USA

Reviews

Canon EF 17-40mm f/4L USM lens (full-frame tests) by cameralabs.com

The Canon EF 17-40mm f/4.0L was announced back in February 2003 as a lightweight ultra wide-angle zoom and has since become a bit of a classic lens for owners of Canon EOS digital and film SLRs.

Its ultra-wide focal range delivers spectacular coverage on film or full-frame digital SLRs, although it’s sufficiently wide to also be considered as a general-purpose zoom on APS-C bodies like the EOS 30D and 400D / XTi. When fitted to an APS-C body, it delivers a range equivalent to 27-64mm, and while the long-end is clearly shorter than general purpose EF-S zooms, it does have the advantage of being compatible with a full-frame body should you wish to upgrade in the future.

Review of the Canon EF 17-40mm f/4L USM Lens by wlcastleman.com

This article reviews the full frame performance of the Canon EF 17-40mm f/4L lens. My intented use of the lens is for landscape photography with a Canon EOS-1Ds camera. The EF 17-40mm f/4L lens (left panel) is a very sharp, high contrast zoom lens with performance characteristics that often match and sometimes exceed those of quality prime lenses at wide angle. Performance drops off slightly in the corners at 35mm, but otherwise this lens is an outstanding performer at a very good price ($670, US Gray Market).