 Low Dispersion
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.
 Extra Refractive Index
More compact lenses with superior image quality
XR (Extra Refractive Index) glass can bend light rays at steeper angles, thereby decreasing the physical length of the lens while enhancing imaging performance by minimising optical aberrations. With its superior light-bending power, XR glass makes it possible to design a short-barrel lens with the same light-gathering ability (aperture value) as a long-barrel lens – even with a smaller lens diameter. By using this principle Tamron has been able to shorten the length of the entire optical system and produce lighter, more compact lenses of the same speed, and also to provide greater zoom ranges in lenses that are much more convenient to carry and hand-hold.
XR glass is costlier than conventional glass but it yields enhanced optical power distribution, making the innovative XR lens designs possible.  Aspherical
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.
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 Precise, quiet autofocus that allows for fine adjustments
The B011's autofocus mechanism uses a stepping motor that's an ideal match for the contrast detection autofocus system used in Sony NEX series cameras. The stepping motor's actuator allows finely tuned control of angular rotation, and since it drives the focusing mechanism directly without an intermediate reduction gear, it also provides superbly quiet performance. You can count on this to enhance autofocus capability when shooting video.
Furthermore, after adjusting with the autofocus mechanism, you can use the Direct Manual Focus (DMF) function to allow delicate adjustments to the image.  Vibration Compensation
Compensates for camera blur on long shutter speeds – for sharp images in much less light
Tamron's unique VC mechanism uses a proprietary actuator and algorithms to deliver an extremely stable viewfinder image with excellent tracking. The mechanism employs a tri-axial system in which three driving coils move internal optical components within the VC lens electromagnetically, based on signals originating from three steel ball bearings. The VC lens elements are held in place only by contact with the steel balls, achieving smooth movement with minimal friction. The simplicity of this mechanical structure is also one of the secrets of Tamron's compact lens sizes.
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18-200mm F/3.5-6.3
for mirrorless interchangeable-lens cameras
for Sony's NEX series E-mount cameras