Canon EF 17-40mm f/4.0L USM
About half the price of the 16-35 f/2.8 lens, this L-series lens has an entirely new optical design with three Aspherical elements and a
Super UD-glass element. The combination provides superb contrast and sharpness, even at the widest settings. It¿s ideal for both film
and digital SLRs, and features the same weatherresistant design, rear gel filter holder, and high-speed Ultrasonic Motor as the
EF 16-35mm lens.
Ultra wide lens for analogue EOS SLR cameras
The EF17-40mm f/4L USM is an ultra wide angle Canon EF zoom lens meant for professional and high amateur SLR EOS camera users.
Standard zoom lens for digital EOS SLR cameras
While it is an excellent lens when used with an analogue SLR camera, the EF17-40mm f/4L USM is especially well suited for digital SLR
cameras with an imaging sensor size smaller than the 35mm format. Indeed on such digital SLR cameras these focal lengths can give an
angle of view approximately equivalent to that of a 28-70mm lens used on a 35mm camera, which makes it the ideal standard zoom lens.
Superior optical performance
The EF17-40mm f/4L USM has 12 lens elements arranged in 9 groups. Super Spectra Coating on the elements ensures excellent colour
balance and minimises ghosting and flare. To provide superb image quality over a 17-40mm zoom range the lens uses three aspheric
elements of two different types, while Super UD (Ultra-low Dispersion) glass is used to prevent the chromatic aberrations that often
can degrade the subject edge clarity.
Extensive set of high-end features
Minimum focusing distance is just 28cm throughout the entire zoom range.
The Auto-focus works silently and quickly thanks to a fast central processing unit with an improved AF algorithm. You can override AF
mode with manual focus should you wish.
Controlled by an electromagnetic diaphragm, the EF17-40mm f/4L USM¿s circular aperture can achieve a more attractive appearance to
out of focus background areas in a picture.
The front of the lens does not rotate as you focus. This means, for example, that polarising filters still function effectively as you zoom in
and out. At the rear of the lens there¿s a drop-in gelatin filter holder.
Highly resistant to moisture and dust, the EF17-40mm f/4L USM is ideally suited for use in harsh environments. Environment friendly
lead-free glass is used throughout its construction.
