A tremendously flexible standard zoom for APS-C-format DSLRs, the EF-S 17-55mm f/2.8 IS USM from Canon pairs the 27.2-88mm equivalent focal length range with a bright f/2.8 constant maximum aperture. Benefitting this design is a sophisticated optical layout, which includes both Ultra-Low Dispersion glass and aspherical elements to significantly reduce chromatic and spherical aberrations for improved clarity and sharpness throughout the zoom range. A Super Spectra coating has also been applied to individual elements to suppress flare and ghosting for increased contrast when working in bright environments.
- Versatile wide-angle to portrait-length zoom is designed for APS-C-format Canon EF-S-mount DSLRs and offers a 27.2-88mm equivalent focal length range.
- Bright constant f/2.8 maximum aperture affords consistent illumination throughout the zoom range and also affords greater control over depth of field for working with selective focus techniques.
- Two Ultra-Low Dispersion glass elements noticeably reduce color fringing and chromatic aberrations for high clarity and color fidelity.
- Three aspherical elements minimize spherical aberrations and distortions for improved sharpness and accurate rendering.
- Super Spectra coating has been applied to individual elements to minimize ghosting and flare for greater contrast and color neutrality when working in strong lighting conditions.
- An Optical Image Stabilizer helps to minimize the appearance of camera shake by up to three shutter speed stops to better enable working in low-light conditions and with slower shutter speeds.
- A ring-type Ultrasonic Motor (USM), along with an internal focusing design and optimized focusing algorithms, is employed to deliver fast, precise, and quiet autofocus performance as well as full-time manual focus override.
- Rounded seven-blade diaphragm contributes to a pleasing out of focus quality that benefits the use of shallow depth of field and selective focus techniques.