This is a newly designed, budget-friendly L-series ultra-wide-angle zoom lens suitable for both film and digital SLRs. Enhanced optics are achieved with three Aspherical lens elements alongside a Super UD (Ultra-low Dispersion) glass element. It features optical coatings tailored for digital cameras. The lens allows focusing as close as 11 inches (0.28m), with Canon's full-time manual focus and a robust ring-type USM for quick and quiet autofocus. It maintains a constant maximum aperture of f/4 and supports either 77mm screw-in filters or a rear holder accommodating up to three gel filters. Its construction is resistant to weather, akin to other premium L-series lenses.

Specifications include an EF Mount L-Series Lens f/4 Super UD, a Ring Ultrasonic Autofocus Motor, Manual Focus Override, Water and Dust Resistance, Internal Zooming and Focusing, and a 77mm Front Filter Thread Diameter.

• Focal Length & Maximum Aperture: 17-40mm; 1:4
• Lens Construction: 12 elements in 9 groups
• Diagonal Angle of View: 104° - 57°30'
• Focus Adjustment: Inner focusing system with USM
• Closest Focusing Distance: 0.28m/ 0.9 ft
• Zoom System: Rotating type
• Filter Size: 77mm
• Max. Diameter x Length, Weight: 3.3 x 3.8, 1.1 lb./83.5 x 96.8mm, 500g