"This highly anticipated lens from Tamron covers the popular 24-70mm range with a fast constant aperture of f/2.8. It is one of Tamron's 'SP' lenses, which denotes that it should be able to produce professional quality results. Unlike lenses in this range from the main camera manufacturers, this optic has Vibration Compensation, which should help to tame camera shake at low shutter speeds. An ultrasonic focusing motor should provide quick focusing speeds, silently with full time manual focus override.
This lens is available in Canon, Nikon and Sony mounts, with the Canon model becoming available first. The Sony compatible model will lack Vibration compensation, as this functionality is already built into Sony DSLR and SLT bodies. As this lens is a 'Di' optic, it is compatible with both full frame and crop sensor camera bodies."
Via
Philippe Gassmann