 "EF 20mm f/2.8 USM"@en "Canon EF USM | Canon Online Store"@en
"Wide-Angle Lens"@en 
 Focal Length & Maximum Aperture 20mm 1:2.8 Lens Construction 11 elements in 9 groups Diagonal Angle of View 94° Focus Adjustment Rear focusing system with USM Closest Focusing Distance 0.25m / 0.8 ft. Filter Size 72mm Max. Diameter x Length, Weight 3.1" x 2.8", 14.3 oz. / 77.5 x 70.6mm, 405g
 "Canon EF 17-40mm f/4 L USM Lens"@en "Camera Lenses :: Canon Lens - Onestop Digital"@en
"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 f4 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.  "@en 