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Rent NowThe Canon EF 17-40mm f/4L USM is a professional-grade ultra-wide-angle zoom lens designed for Canon EF-mount cameras, developed as a more affordable alternative to Canon’s faster 16-35mm f/2.8L zoom while still delivering L-series optical performance and build quality. As part of Canon’s L-series lineup, it’s aimed at landscape, architecture, interior, and travel photographers who want genuine wide-angle coverage without the higher cost of a constant f/2.8 ultra-wide zoom.
Optically, the lens covers a 17-40mm focal range with a constant f/4 maximum aperture throughout the zoom, simplifying exposure calculations compared to variable-aperture designs. The optical construction, 12 elements in 9 groups, incorporates one Super UD (ultra-low dispersion) glass element to minimize chromatic aberration and color bleed common in wide-angle lenses, along with three aspherical elements (one high-precision molded glass and two replica aspherical elements) to correct for various aberrations that arise during zooming. Canon’s Super Spectra coating is applied to suppress flare and ghosting for improved contrast in difficult lighting, and a 7-blade circular diaphragm contributes to smoother background blur than earlier Canon wide-angle zooms.
Autofocus is handled by a ring-type USM motor with an internal focusing mechanism, delivering fast, quiet, and accurate autofocus along with full-time manual focus override. A notable strength of this lens is its close minimum focusing distance of just 0.28m (11 inches) across the entire zoom range, yielding a maximum magnification of 0.24x at 40mm, giving photographers unusual close-up flexibility for an ultra-wide zoom.
As an L-series lens, the EF 17-40mm f/4L USM features weather-sealed construction, and notably holds the distinction of being the lightest and smallest L-series zoom lens Canon has produced, weighing approximately 475g (1.1 lb) and measuring 83.5 x 96.8mm, with a fixed length that does not extend at any focal length. The lens accepts 77mm front filters, and also includes a rear filter holder accommodating up to three gel filters. It does not include image stabilization, consistent with its lighter, more affordable L-series positioning.
As a full-frame-compatible lens, the EF 17-40mm f/4L USM produces its full ultra-wide angle of view on full-frame Canon bodies and an effective 27-64mm equivalent field of view on APS-C bodies (1.6x crop), making it a versatile option across Canon’s camera lineup.
Key Features
– 17-40mm constant f/4L ultra-wide-angle zoom for Canon EF mount
– 12 elements in 9 groups, including 1 Super UD element and 3 aspherical elements
– Super Spectra coating
– Ring-type USM autofocus with full-time manual focus override
– 7-blade circular diaphragm
– L-series weather-sealed construction
– Lightest and smallest L-series zoom lens in Canon’s lineup
– Minimum focusing distance of 0.28m (11″) across entire zoom range
– Maximum magnification of 0.24x (at 40mm)
– 77mm filter thread, plus rear gel filter holder (up to 3 filters)
– No image stabilization
– Approximate weight: 475g (1.1 lb)
– Compatible with full-frame and APS-C Canon EF-mount cameras
