Tamron's SP 24-70mm f/2.8 DI VC USD Lens for Nikon Cameras delivers a very useful range from 24mm true wide-angle to 70mm short telephoto, useful for landscapes, interiors, portraits, street photography and much more. The continuous maximum aperture of f/2.8 combined with built-in Vibration Compensation image stabilization make it possible to achieve stellar results in low-light situations, while the Ultrasonic Silent Drive (USD) gives you very quiet autofocus capabilities that are ideal for shooting video.
The 24-70mm lens uses specialized high-grade glass in the three LD elements, three Glass Molded Aspherical Lenses, one Hybrid Aspherical Lens and two XR (Extra Refractive Index) glasses, for excellent image quality. Using a rounded 9-blade diaphragm, the lens delivers fine bokeh--the out-of-focus area in a photo. Moisture-resistant construction helps protect the lens from any water that comes near it. And all of this is in a compact (3.5 x 4.6"), lightweight (29.1 oz) package that won't wear you out, even carrying it all day.
VC (Vibration Compensation) is Tamron's proprietary image stabilization system. Tamron's VC is a three-coil system, whereby three driving coils activate the shake-compensating VC lens group electromagnetically via three steel balls. The VC lens elements are held in place only by contact with the steel balls, achieving smooth movement with little friction. This provides a stable viewfinder image with excellent tracking performance. And as the VC lens may be moved in parallel using only the motorized control, the mechanical structure has been simplified, enabling the creation of a more compact lens.
Tamron's original VC image stabilization mechanism utilized a moving magnet system whereby a heavy magnet was positioned near the moving VC lens element. In the new VC unit the positions of the magnet and the coil are reversed, because of this the VC optical lens element is attached to the coil. The new VC mechanism employs a moving coil mechanism with a lightweight coil, and the lighter coil reduces the load on the drive system. Thus, the lighter, more compact new VC unit contributes to the lens's overall light weight and compact size. Because the 24-70 mm F/2.8 Di VC USD is a high-speed zoom lens with maximum aperture of F/2.8, its VC system must drive a lens that is larger and heavier than other zooms. Therefore, the shape, size and layout of the drive coils are all designed to obtain sufficient thrust. The result is a full-size, high-speed zoom that provides the same high level of compensation effect.
In the ultrasonic motor, a piezoelectric element arranged in a ring formation generates ultrasonic vibrations in a metallic ring stator, and the vibration energy is used to rotate a metallic ring rotor that is attached to the stator. The rotation energy is in turn transferred from the metallic ring rotor to operate the focus lens.