In the pursuit to achieve the most outstanding image resolution in the 70-300mm class, Tamron’s Anniversary lens – the SP AF70-300mm F4-5.6 Di VC USD – utilizes an advanced optical design that features a LD ( Low Dispersion) and an XLD (Extra Low Dispersion) lens element made from specialized materials that prevent chromatic aberration. As a result, the SP AF70-300mm F4-5.6 Di VC USD boasts sharper contrast and greater descriptive performance than all others in its class. In addition, it is the first Tamron lens to include a USD ( Ultrasonic Silent Drive), Tamron’s very own ultrasonic auto-focus drive mechanism. This USD mechanism delivers fast focusing, making it a perfect telephoto zoom choice for photographing sports, racing, or other fast-moving subjects. The lens also boasts Tamron’s proprietary VC* ( Vibration Compensation) image stabilization to assist in hand-held photography, not only at long focal length ranges where blurring is common, but also under low-lit conditions, dramatically enhancing photographic freedom. This combination of best in class image resolution, Ultrasonic Silent Drive and Vibration Compensation is a new achievement of Tamron technology, culminating in the production of a premium 70-300mm telephoto zoom lens. *Please note: The Sony mount does not include VC technology, due to the fact that most Sony SLRs have an integrated image stabilizer.