In developing the 70-210mm F /4 (model A034), Tamron was able to draw on its long and extensive expertise in telephoto zoom lens design. The result is a compact lens with outstanding imaging performance for shooting with very high resolution and excellent contrast ratio at a weight of 850g. The optical construction consists of 20 elements in 14 groups, including 3 LD (low dispersion) elements for the correction of chromatic aberration and lateral chromatic aberration. With a maximum magnification of 1:3.1, the Tamron 70-210mm F/4 has the largest magnification in its class. The short closest focusing distance of 0.95 cm allows the photographer to take fascinating close-ups of flowers, animals and other small objects. The Dual MPU (Micro-Processing Unit) controls the ultrasonic autofocus and VC image stabilizer using two powerful microprocessors. Both have a DSP (Digital Signal Processing) unit for accelerated data processing, which increases the overall performance of the telephoto zoom lens. The precise ultrasonic autofocus of the 70-210mm F /4 is based on a responsive ring motor. If desired, the focus point can be manually shifted via the manual focus ring without having to deactivate AF mode. Like Tamron's SP series, the telephoto zoom features VC image stabilization, which allows up to 4 stops longer exposure times according to CIPA standards. This allows for sharp freehand shots even in low light and at slower shutter speeds. Internal focusing prevents the length of the 70-210mm F /4 from changing when zooming or focusing. As a result, the solid and robustly constructed lens always remains optimally balanced, allowing for more precise operation and more accurate image composition. Because of the consistent overall length, the photographer does not have to move the camera backward when shooting through a fence or a pane of glass to avoid accidentally adjusting the focal length by bumping the lens.