Canon's EF 17–40mm f/4L USM is an advanced wide-angle zoom lens in Canon's L Series. This lens is for full frame and APS-C size ESLR cameras. Its unique construction features 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. Extremely useful for close-up work, this lens sports a minimum focusing distance of just 11" (28cm) throughout its entire range of focal lengths. It 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.
Canon L Series
The L Series denotes Canon's professional line of lenses. Though used extensively by non-professionals, these lens have been engineered to the highest of standards. These luxury lenses incorporate such advanced optical advantages as Super Low Dispersion Glass, Ultra-Low Dispersion Glass, flourite elements and aspherical design elements. All of these combine to produce reliably incredible images.
Ultra Sonic Motor (USM)
Canon's USM lenses employ a motor powered by ultrasonic waves that produce a quiet, yet high-speed AutoFocus. You can enjoy high performance with low noise in a variety of shooting situations.
Ultra Low Dispersion Glass
Canon's Low Dispersion technology is engineered to reduce chromatic aberrations, eliminating the tendency of light of different colors to focus to different points at the image plane. This means your images will come out crisp and clear, with less of a chance of defracting light into an unwanted rainbow of colors. Take shots exactly like you want, without any flare-up or blurring.
Manual focusing means you have all the control at the end of your fingers. Canon lenses feature a specially designed ergonomic construction that is noticeable at first touch. The large rotation angle of this lens guarantees precise focusing. The mechanism moves super smoothly and without extra play.
The Canon anti-reflective coating is an optical design feature which ensures superior clarity and image brilliance, even in poor or unfavorable lighting conditions. Canon applies the anti-reflective coating through a special process, layering the lens surface in order to substantially reduce unwanted flare or ghosting. This process helps to ensure incredibly rich image contrast and true color fidelity. Canon L Series lenses feature a fluorine coating on the front and rear surfaces. This coating helps to greatly reduce smears, smudges or fingerprints ensuring that you will always take impeccable images.
Optical Image Stabilization (IS)
Lens features Optical Stabilization technology, a feature that employs an innate, built-in mechanism in order to compensate for camera shake. By eliminating natural shakes and sways with camera movement your images will come out crisp and clean every time.
- Focal Length: 17-40mm
- Aperture Range: f/4
- EF Mount L-Series Lens
- Full-Frame Format
- Optical Image Stabilization
- Ring Ultrasonic Autofocus Motor
- Water and Dust Resistant
- Internal Zooming and Focusing
- 77mm Front Filter Thread Diameter
- Truly Circular Diaphragm
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