The lens which I like

Amstelveen, The Netherlands, 21 February, 2006: Canon today strengthens its EF-S lens series with the Image Stabilized wide angle EF-S 17-55mm f/2.8 IS USM. With image quality and construction approaching that of Canon’s renowned professional lenses, the EF-S 17-55mm f/2.8 IS USM becomes the fastest standard focal length zoom for EF–S mount cameras such as the new EOS 30D. Combining constant f/2.8 aperture throughout the zoom range with Canon’s latest 3-stop Image Stabilizer, it delivers outstanding wide angle performance and framing flexibility in low light conditions. Specialist optics such as UD glass and aspherical elements help deliver exceptional clarity, sharpness, contrast and colour accuracy.
EF-S mount
The lens fits exclusively on those EOS cameras with an EF–S lens mount – the new EOS 30D, EOS 350D, and earlier EOS 20D and 300D models. (see appendix‘Technologies Explained for further information on the EF–S mount). The 1.6x multiplication effect of these cameras’APS-C size sensor gives the lens an effective focal length of approximately 27-88mm.
Image quality
To improve image clarity over the total image area, two Ultra-Low Dispersion glass (UD) elements are employed to eliminate secondary chromatic aberrations that otherwise reduce sharpness and introduce colour fringing. To ensure crisp, high contrast from one corner of the frame to the other, two aspherical lens elements have been introduced to avoid spherical aberrations that can soften images, especially at wider apertures. In combination with digital EOS CMOS sensor and DIGIC II image processor technologies, the EF-S 17-55mm f/2.8 IS USM delivers image quality surpassing that required for many commercial applications.
Fixed f/2.8 from 17 – 55mm
Superb optical quality with no change in aperture over the full focal length range allows photographers to set exposure at the widest aperture and concentrate on framing, without concern for adjusting shutter speed at longer focal lengths. The lens employs an almost perfectly circular barrel aperture, helping create attractive, even background blur.
Image Stabilizer
The lens features Canon’s latest 3-stop Image Stabilizer (IS) for dramatically reduced image blur caused by camera shake. IS significantly extends scope for shooting in low light conditions without flash, or for gaining depth of field. The 3-stop advantage allows a photographer shooting in low light to use a shutter speed of just 1/15 sec instead of 1/125, with no perceptible increase in image blur.
IS automatically detects when the camera is mounted on a tripod, thus preventing feedback loops between the IS sensor and stabilizer motor vibrations.
(See more information on Image Stabilizer, see appendix‘Technologies Explained’).
Fast, silent auto-focus
The lens’USM motor employs ultrasonic frequency vibrations to drive auto focus with speed and near-silent operation. The constant torque motor moves the focus group at high speed, stopping with precision, accuracy and without overshoot the instant the lens arrives at the correct focus point. Photographers can switch to manual focus instantly and at any time simply by moving the manual focus ring without first having to switch out of auto focus mode.
Harmful reflections eliminated
By optimising Super Spectra lens coatings and lens element shaping, Canon’s engineers have been effective in suppressing flare and ghosting – more prone to occur with digital cameras due to reflection off the image sensor. By increasing light absorption, coatings reduce reflections off lens element surfaces to deliver crisp, undistorted images with natural colour balance.

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