The Canon EF 17‑40mm f/4L USM is a professional wide‑angle zoom lens in Canon’s L‑series, designed for the EF mount used on full‑frame and APS‑C digital single‑lens reflex (DSLR) cameras.
Key specifications
- Focal length: 17 mm to 40 mm (35 mm‑format equivalent)
- Maximum aperture: Constant f/4 throughout the zoom range
- Lens construction: 9 elements arranged in 8 groups, including one aspherical element and two ultra‑low‑dispersion (UD) elements to reduce chromatic aberration
- Autofocus system: Ring‑type Ultrasonic Motor (USM) providing fast, silent focusing and full‑time manual focus override
- Minimum focusing distance: 0.28 m (approximately 0.9 ft)
- Maximum magnification: 0.12×
- Filter thread: 77 mm diameter
- Physical dimensions: Approximately 79 mm in maximum diameter and 92 mm in length
- Weight: Roughly 590 g (about 1.3 lb)
- Features: Weather‑sealed construction typical of L‑series lenses, brass mount, and a 7‑blade (rounded) diaphragm for relatively smooth bokeh.
Release and positioning
The lens was introduced by Canon in 2004 as an L‑series alternative to the earlier EF 17–35 mm f/2.8 and as a more compact, lighter option for photographers needing a fast, constant‑aperture wide‑angle zoom. It is positioned for professional and enthusiast use in fields such as landscape, architecture, interior, and event photography where a wide field of view and consistent exposure are advantageous.
Compatibility
- Full‑frame (EF‑mount) cameras: Provides true 17‑40 mm coverage.
- APS‑C (crop‑sensor) cameras: The effective field of view becomes approximately 27‑66 mm (1.6× crop factor for Canon APS‑C bodies).
Reception
The lens is widely regarded for its solid build quality, good optical performance, and relatively compact size compared with other L‑series wide‑angle zooms. Reviews commonly note its sharpness center‑to‑edge at the wide end, reliable autofocus, and suitability for demanding professional work, while also pointing out that its maximum aperture of f/4, while constant, is slower than some competing f/2.8 lenses.
References
- Canon Inc., official product specifications (archived product pages, 2004–present).
- Independent photographic equipment reviews and technical assessments published in reputable photography journals and websites.
