XGM eXpanded Glass Molded Aspherical
Corrects aberrations typical to wide-angle lenses
A large diameter XGM (eXpanded Glass Molded Aspherical) lens element is featured 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.
Compared to a previous Molded-Glass Aspherical element (left), XGM has a larger aspherical surface.
Far superior image quality – while reducing lens size and weight
Tamron uses several hybrid aspherical lens elements in its lenses bearing the Aspherical designation. The benefits are two-fold: first, their non-spherical shapes virtually eliminate spherical aberration and image distortion. Second, as one hybrid aspherical lens element can take the place of multiple elements without compromising performance, they allow the lens to be much more compact.
As a result, these innovative optics have played a crucial role in delivering uniformly high image quality across all apertures and focal lengths of extraordinarily compact ultra-zoom lenses.
Sharpens edges by reducing ‘colour fringing’
Chromatic aberration occurs when a lens element refracts different wavelengths of a ray of light – its rainbow colours – at very slightly different angles. This results in the ‘colour fringing’ that reduces the sharpness of an image. LD elements are made from special glass materials with extremely low dispersion indices (i.e. the refraction of a ray of light into rainbow colours is extremely narrow). Thus they effectively compensate for chromatic aberration at the centre of the field (on axis), a particular problem at long focal lengths (the telephoto end of the zoom range), and for lateral chromatic aberration (toward the edges of the field) that often occurs at short (wideangle) focal lengths.
Although costly, LD glass materials result in clear, vivid image quality.
Attention-grabbing blur effects at wider apertures
Use depth of field more creatively with spectacular but natural-looking background blur.
The rounded outline diaphragm of the lens is retained even when stopped down to f/5.6. Blur highlights in a photo reflect the shape of the aperture, and they are a much more prominent feature at wider apertures. Especially in higher-speed lens, this important optical design element results in more attractive, natural-looking images.
Advanced lens coating produces even sharper, crisper images
This new coating technique developed by Tamron deploys a nano-structured* layer with dimensions smaller than the wavelengths of visible rays of light. Called eBAND (extended Bandwidth & ANgular-Dependency), its ultra-low refractive index, combined with the sophisticated multiple-layer coatings underneath, yields significant anti-reflection properties, absolutely minimising flare and ghosting to deliver sharp, crisp images.
*1nm = 1/1,000,000mm
Broad-Band Anti-Reflective coating
Cleaner, crisper images without flare or ghosting
For the precision required by digital sensors, Tamron’s BBAR (Broad-Band Anti Reflection) multilayer coatings reduce reflection into the lens elements, enhancing light transmission on both long and short wavelengths. Internal surface coatings are also applied on cemented surfaces of lens elements to make images sharper with better colour balance and reproduction.