The Canon 17-40mm f/4 USM is an affordable L-series ultra-wide-angle zoom lens that's ideal for both film and digital SLRs. This EF lens focuses as close as 0.28m. 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 3 gel filters. The 17-40mm f4L also features a wear-resistant construction.
Key Features: Canon EF 17-40mm f/4 L USM Lens
Superb optical performance throughout the zoom range Fast autofocus speed Highly resistant to dust and moisture 28cm minimum focusing distance at all focal lengths
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 3 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.
Aperture Blades 7 Autofocus Motor USM Colour Black Enlargement Ratio 1:4.2 Filter Thread Size (mm) 77 Focal Length – Tele (mm) 40 Focal Length – Wide (mm) 17 Hood Model EW-83E Included Accessories Lens pouch, Front and rear caps, Lens hood Lens Mount Canon EF Lens Type Standard Zoom Manual Focus Switching Full Time Manual Override Maximum Aperture – Tele 4 Maximum Aperture – Wide 4 Minimum Aperture 22 Number of Lens Elements 12 Number of Lens Groups 9 Sensor Format Full Frame Size (mm) 83.5 x 96.8 mm Weight (g) 500 MF switch Full Time Manual Override Minimum Focus Distance (m) 0.3