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Ultra wide lens for analogue EOS SLR cameras
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The EF17-40mm f/4L USM is an ultra wide angle
Canon EF zoom lens meant for professional and high amateur SLR EOS camera
users. |
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Standard zoom lens for digital EOS SLR
cameras |
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While it is an excellent lens when used with
an analogue SLR camera, the EF17-40mm f/4L USM is especially well suited for
digital SLR cameras with an imaging sensor size smaller than the 35mm format.
Indeed on 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. |
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Superior optical performance |
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The EF17-40mm f/4L USM has 12 lens elements
arranged in 9 groups. Super Spectra Coating on the elements ensures excellent
colour balance and minimises ghosting and flare. To provide superb image
quality over a 17-40mm zoom range the lens uses three aspheric elements of two
different types, while Super UD (Ultra-low Dispersion) glass is used to prevent
the chromatic aberrations that often can degrade the subject edge clarity.
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Extensive set of high-end features
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Minimum focusing distance is just 28mm
throughout the entire zoom range. |
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The Auto-focus works silently and quickly
thanks to a fast central processing unit with an improved AF algorithm.
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You can override AF mode with manual focus
should you wish. |
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Controlled by an electromagnetic diaphragm,
the EF17-40mm f/4L USM's circular aperture can achieve a more attractive
appearance to out of focus background areas in a picture. |
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The front of the lens does not rotate as you
focus. This means, for example, that polarising filters still function
effectively as you zoom in and out. |
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At the rear of the lens there's a drop-in
gelatin filter holder. Highly resistant to moisture and dust, the EF17-40mm
f/4L USM is ideally suited for use in harsh environments. Environment friendly
lead-free glass is used throughout its construction. |
