This lens advanced optical design employs a sophisticated XLD (Extra Low Dispersion) lens element made from specialized high-grade glass that has lower dispersive properties than standard LD lenses (where refraction causes the dispersion of white light into spectral hues). The dispersive properties of the XLD lens are at a level similar to fluorite, and in combination with LD elements make for an optimal optical design that delivers best in class resolution with advanced axial chromatic and magnification aberration correction - major inhibitors of image quality enhancement. The result is a lens that delivers sharp contrast and better descriptive performance throughout the entire zoom range.

The lens is equipped with Tamron's first-ever ultrasonic auto-focus drive USD (Ultrasonic Silent Drive). It achieves faster focusing making this telephoto lens perfect for photography of sports, motor racing, and other fast-moving subjects. With advanced motor technology and newly developed software, Tamron's USD delivers precise and noiseless focusing at turbo speed.

USD (Ultrasonic Silent Drive)
Tamron's USD works with the high-frequency ultrasonic vibrations that are produced by a ring called a 'stator'. Energy from the vibrations is used to rotate an attached metallic ring known as the 'rotor'. Piezoelectric ceramic, an element that produces ultrasonic vibrations when voltage of a specific frequency is applied is arranged in a ring formation on the stator. This electrode configuration of piezoelectric ceramic causes two ultrasonic vibrations to occur in the stator.
By effectively combining these two ultrasonic vibrations, it is possible to convert the energy from the vibrations that produced simple motion into energy known as 'deflective traveling waves', which then moves around the circumference (rotation direction) of the ring.
With the USD, the friction between these deflective traveling waves created on the metallic surface of the stator and the surface of the rotor produce force, causing the rotor to rotate. The focusing ring lens, which is linked to the rotor, is thus moved, creating a fast and smooth auto-focus drive.

The SP 70-300mm F4-5.6 Di VC USD employs Tamron's esteemed image stabilization mechanism-VC (Vibration Compensation) seen in both the AF18-270mm Di II VC (Model B003) and SP AF17-50mm F/2.8 XR Di II VC (Model B005). With VC, the photographer has the freedom to shoot at a shutter speed that is an extra four stops slower without having to worry about blurring. This makes capturing handheld, evening, night, and interior shots much easier.

VC (Vibration Compensation)
Tamron's VC mechanism employs 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 that eliminates the blur from camera shake for cleaner, crisper shots.

Auto-focus has many benefits but sometimes the photographer needs the control of manual focus. Full time manual offers just that: the crossover from auto-focus to manual focus by simply adjusting the focus ring, allowing the photographer to make adjustments on the fly. This feature helps the lens produce impressive results even in telephoto situations where the depth of field is narrow.

When focusing, the internal elements of the lens move and the lens' external size does not change. This offers better balance and easier telephoto shots. Moreover, the barrel is not subject to stray light entering from external helicoids that can negatively affect images. And because the external elements do not move, it makes it easier to utilize polarizing filters and the flower shape hood to control the amount of light that enters the lens.

With a full-frame digital or 35mm SLR, portrait and medium telephoto shots can be achieved on the wider 70mm end of the range and spectacular telephoto shots at the longer 300mm side. When using an ASP-C sensor camera the angle of view changes, giving it the equivalent range of 109-465mm for bold ultra-telephoto shots. And with a maximum magnification ratio 1:4, the lens can be used to explore in the realm of semi-macro photography.
*Tamron's conversion value is 1.55 x

Digital photography requires extreme precision, which is why Tamron incorporates new BBAR (Broad-Band Anti Reflection) multilayer coatings that reduce reflection into the lens elements. This ensures excellent performance in all photographic conditions and enhances light transmission on both long and short wavelengths. Also, Tamron applies internal surface coatings on cemented surfaces of lens elements to make images sharper with better color reproduction and balance.

Tamron adopted a simple design with a smooth silhouette to ensure that this lens fits well with various SLR cameras. The exquisite textured paint gives a well-crafted finish to the exterior.

The flower-shaped hood has been designed specifically to block out damaging light rays and ensures clear, sharp descriptive performance.