While this is an excellent ultra-wide zoom lens for analogue (film) SLR cameras, this lens is especially well suited for digital SLR cameras which usually have an imaging sensor size smaller than the 35mm format.
When used with 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.
All of the "L" lenses deliver optical performance equal to similiar fixed focal length lenses, and the USM lenses do this with silent, high-speed focusing.
Distortions and aberrations are remarkably small for a lens of such amazing capabilities.
• 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,83.5mm x 96.8mm,3.3'' x 3.8'',
• Weight: 1.1 lbs. / 500g