From the Manufacturer:
Get closer to the action with a G-Series telephoto zoom lens featuring an uncommonly fast f/2.8 aperture with quiet, high-speed SSM (Super Sonic wave Motor) auto-focus precision ideal for long-distance sports, wildlife photography and more. This superb 70-200mm zoom lens is an excellent choice for a wide range of medium to long-distance telephoto applications. (35mm equivalent when used with APS-C format cameras: 105-300mm.) With the ability to focus as closely as 3.9 feet (1.2m), this telephoto lens also lets you move in for dramatic shots of people, natural subjects and close-up details.
The fast f/2.8 aperture enables shooting at much higher shutter speeds to freeze action. This lens, like all in Sony's G-Series, is designed for maximum descriptive power, maintaining excellent peripheral light characteristics and maximizing contrast even at the edges of the frame. Two ED (Extra-low Dispersion) glass elements minimize chromatic aberration for sharp, clear images with well defined colors. This lens incorporates 19 elements in 16 groups for high optical precision from the center of the image all the way to the corners. Because the 9 aperture blades form a near circle at the wide openings used for low-light shots, spot-light sources have a pleasing circular defocused effect.
This lens also features indispensible SSM (Super Sonic wave Motor) technology. Designed for fast, smooth, silent automatic focusing, this unique technology achieves high torque at low speed with rapid start/stop response. It operates through the ability of a piezoelectric device to reshape itself quickly when voltage is applied. Its focus range limiter option is used when you need the quickest possible autofocus response within a certain focal range. The lens will only autofocus within the set range eliminating AF at focal lengths outside.