From the Manufacturer:
Get a superb all-purpose telephoto zoom lens at a great value with the Sony SAL55300 55-300mm f/4.5-5.6 lens. An excellent all-around addition to your kit, this lens covers the medium- to long-distance telephoto range used most often by family photographers. It also provides close minimum focusing distance of about 4.5 feet (1.4m) ideal for tight shots of people, natural subjects and close-up details. Its compact, lightweight design makes it easy to carry as your standard or accessory lens. All your shots will benefit from the Sony Super SteadyShot image stabilization system built into your Sony Alpha DSLR camera. (35mm equivalent: 82.5-450mm)
Compact Design, All-Around Versatility
This high-value 55-300mm zoom lens covers a wide range of medium to long-distance telephoto applications -- and its lightweight design lets you leave it on-camera or carry it easily as an accessory lens for special purposes (35mm equivalent: 82.5-450mm).
In-Camera Image Stabilization
A major reason for its compact, lightweight design is the benefit of Super SteadyShot in-camera image stabilization, built into every Sony system DSLR -- and enabling accessory lenses to eliminate the extra weight and expense of in-lens stabilization mechanisms.
Advisory when using DT lenses with full-frame (35mm equivalent) DSLR cameras.
Sony alpha lenses with the Digital Technology (DT) designation are ideal for use on APS-C size DSLR cameras and are not recommended for use with full frame DSLR camera bodies (such as the DSLR-A900). Although DT lenses can be used with full frame cameras, they can only realize a maximum of 11MP image size (when using the DSLR-A900), and are not guaranteed to provide accurate Auto Exposure performance.
DT Lens Design
The SAL-55300 is specially designed for the APS-size CCD imager used in Sony alpha DSLR cameras. APS-size sensors are smaller than a 35mm-format film frame, so the focal distance to cover the same field of view can be about 2/3 shorter -- allowing a more compact lens design.
The SAL-55300 is designed with 12 lens elements in 9 groups, with precision focusing performance and smooth zoom operation.
Short Minimum Focusing Distance
With the ability to focus as closely as 4.5 feet (1.4m), this telephoto lens also lets you move in for dramatic shots of people, natural subjects and close-up details.
ED (Extra-low Dispersion) Glass
Because light of different wavelength (or color) bends at different angles when it passes through a lens, ED (Extra-low Dispersion) Glass is used to eliminate chromatic aberration by correcting certain wavelengths of light for sharp, clear images with well defined colors.