A large diameter XGM (eXpanded Glass Molded Aspherical) lens element is placed in the first lens group of a system that also includes several LD (Low Dispersion) elements in its 18-element, 13-group optical design. This combination effectively controls distortion and chromatic aberrations that typically affect wide-angle lenses.

XGM (eXpanded Glass Molded Aspherical):
The XGM (eXpanded Glass Molded Aspherical) lens element is capable of efficiently correcting aberrations in the angle of view that changes significantly with an ultra-wide-angle zoom lens. It has an especially significant impact on minimizing distortion and enhancing the sharpness of the image at its periphery.
Furthermore, the molded-glass manufacturing method allows the fabrication of a wider range of lens shapes than the composite aspherical lens method. Moreover, XGM also effectively controls aberrations and reduces total lens size. (Left：Conventional Molded-Glass Aspherical lens element, Right：XGM lens element)

Responding to the demand for a wide-angle lens suited for handheld shooting at slow shutter speeds, Tamron has created the world's first F/2.8 ultra-wide-angle zoom lens with image stabilization. The result is a lens able to capture sharp images even when shooting handheld under low light conditions.

This system employs three coils that move the optical compensation system electromagnetically via three ceramic ball bearings. It offers excellent stability and enables smooth movement with little friction. When equipping 15-30mm with VC, the design of the VC unit was optimized for a fast F/2.8 aperture ultra-wide-angle zoom lens.

The VC unit was made compact to prevent the body of the lens from becoming too large when equipping this fast F/2.8 aperture ultra-wide-angle zoom lens with the Vibration Compensation mechanism. Each VC unit is exclusively designed and optimized for each lens that incorporates this exclusive feature.

Moisture-resistant construction helps prevent moisture from penetrating the lens.

The lens offers the high levels of durability and operability expected in an SP lens, based on its exacting design specifications. Many of the components used in the lens' drive unit, such as those in the zoom and focus mechanisms, are made of metal (aluminum alloy). Their high level of manufacturing and assembly precision has resulted in a high-precision lens body that resists wear and deterioration over time. The zoom ring uses zoom mechanisms and cam arrangements refined over the course of Tamron's long history of high-power zoom lens development, providing smooth operation under variable torque. The focus ring employs a holding mechanism optimized for the USD (Ultrasonic Silent Drive), offering smooth torque during MF operation.

The integrated lens hood features a unique Tamron zoom-linked double-hood design which resists physical shocks such as accidental drops. It is designed to minimize damage to the lens.

Using state-of-the-art optical design, the lens provides advanced compensation for the optical aberrations common with ultra-wide-angle lenses, such as distortion and lateral chromatic aberration. In particular, lateral chromatic aberration is accurately corrected by using concave LD elements. This provides clear images with high resolution and enables high quality wide-angle images.

The high sharpness and contrast provided by this lens make it possible to accurately capture even the finest details of the subject. The superior imaging capability of the lens renders point light sources as sharp points, even in peripheral areas. This lens is therefore perfect for landscape, night, and astrophotography, all of which require high resolution across the entire frame.

This lens also takes into account the appearance of the areas at the corners of the frame. The clearly protruding front lens has a deep curvature designed to prevent peripheral light fall off. Even at its maximum aperture, there is very little observable or measurable peripheral light fall off.

The 9-blade diaphragm construction stays a nearly circular aperture even when stopped down two steps from its maximum aperture. It therefore maintains its ability to capture soft bokeh effects even when the aperture is stopped down.