Canon EF 17-40mm f/4L USM

This super wide-angle zoom lens allows you to take wide photographs even with digital SLR cameras which have a screen size smaller than 35mm, covering the range from a super wide-angle 17mm to a standard 40mm. Three aspherical lens elements which come in two types deliver both a wide zoom range and high image quality, while the super UD lens elements provide excellent correction of the magnification-type chromatic aberration. Innovations such as a lens coating optimized for digital photography help minimize flare and ghosts, which often occur with digital cameras. The circular aperture diaphragm which brings out a nuanced blur and the achievement of a closest focusing distance of 0.28m over the whole range of the zoom, not only help you in composition, but the quiet, high-speed autofocus and the outstanding dust-proof*1 construction make this lens extremely mobile. The front filter mount does not rotate during focusing, so there is no problem when using circular PL filters or other filters, and in combination with the EF70-200mm f/4L IS USM you can get the right shot almost anywhere you go.

Features

• Superb optical performance throughout the zoom range
• Fast autofocus speed
• Highly resistant to dust and moisture
• 28cm minimum focusing distance at all focal lengths

KEY FEATURES

Ultra-wide or standard zoom
The EF 17-40mm f/4L USM acts as an ultra-wide angle zoom on film or full-frame digital EOS cameras. On DSLRs equipped with APS-C sized sensors it acts as a standard zoom, giving an angle of view equivalent to a 28-70mm lens on a full-frame camera.

Close focusing
Minimum focusing distance is just 28cm throughout the entire zoom range.

Superior optical performance
The EF17-40mm f/4L USM has 12 lens elements arranged in nine groups. Super Spectra coating ensures excellent colour balance and minimises ghosting and flare. To provide superb image quality over the complete 17-40mm zoom range the lens uses three aspheric elements. Super UD (Ultra-low Dispersion) glass prevents chromatic aberrations.

Ultrasonic focusing
A ring-type ultrasonic motor drives autofocus extremely quickly, and in near silence. Excellent holding torque ensures the point of focus is reached accurately, without overshooting. Furthermore, full-time manual override is available, making it possible to adjust focus without leaving AF mode.

Non-rotating front element
The front of the lens does not rotate, which makes using specialised filters, such as polarisers and graduates, easier. A drop-in gelatine-filter holder can be found at the back of the lens.

Smooth background blur
A virtually circular aperture diaphragm gives out of focus regions a softer, more uniform feel. Sharp foreground objects stand out against a smooth blurred background.

Weather resistant
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.