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.
Controls the dispersion of specific wavelengths of light
AD glass is a special type of optical glass that is used to achieve more precise control of chromatic aberrations, thereby enhancing overall imaging performance. Glass of this type provides an abnormally large partial dispersion ratio (amount of diffraction) for light of specific wavelength ranges (colours) within the visible spectrum. By combining AD glass having these special characteristics with elements made of normal glass having different dispersion characteristics, it is possible to control the dispersion factors of a specific wavelength.
This enhanced level of control results much lower levels of on-axis (central) chromatic aberration for telephoto lenses (or zooms used at telephoto settings) and a significant reduction of lateral (peripheral) chromatic aberration for wide-angle lenses (or zooms used at wideangle settings).
Like LD glass, AD glass material is costly but provides clear, vivid image quality.
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.
Broad-Band Anti-Reflective coating
Cleaner, crisper images without flare or ghosting
BBAR (Broad-Band Anti-Reflection) coatings reduce the lens reflection and dispersion that cause ghosting and flare. The coatings enhance light transmission in both the short and long wavelength ranges, ensuring excellent performance in all photographic conditions. Additionally, internal surface coatings are applied to cemented surfaces of all lens elements to deliver sharp, high-contrast images and flawless colour reproduction.
Stabilises camera blur for sharp images in low light
If you're shooting handheld when light is low, especially with longer lenses, your camera's shutter speeds can extend to a point where the image may turn out blurred due to camera shake. Tamron's VC tracks this shake and neutralises it for sharper images without the inconvenience of a tripod or the artificiality of a flash, in much lower light.
Tamron's unique VC mechanism uses a proprietary actuator and algorithms to deliver an extremely stable viewfinder image with excellent tracking. The tri-axial system uses three driving coils to move internal optical components within the VC lens electromagnetically, based on signals originating from three ball bearings, made from either steel or ceramic. The VC lens elements are held in place only by contact with the balls, achieving smooth movement with minimal friction.
Tamron's original moving magnet system employed a heavy magnet positioned near the moving VC lens element. The improved VC reverses the positions of magnet and coil and attaches the VC optic to the coil. This moving coil is lighter than the magnet, and as this reduces the load on the drive system, both the VC unit and the lens are lighter and more compact.
Minimum focus distance of 49cm over the zoom range, with macro capability to 1:3.8
Designed exclusively for APS-C sized digital SLR cameras, this all-in-one zoom covers every angle. Its minimum focal distance of 0.49m (19.3 in.) through the entire zoom range and macro capability to 1:3.8 allows you to enjoy serious, high-quality macro photography with astonishing convenience.
|Focal length||18-270mm (28-419mm equivalent)|
|Angles of view||Diagonal: 75°33' - 5°55'
Horizontal: 65°36' - 4°55'
Vertical: 46°21' - 3°10'
|Lens construction||16 elements in 13 groups|
|Minimum focus distance||0.49m (19.3 in.)|
|Maximum magnification ratio||1:3.8 (at f=270mm and MFD 0.49m)|
|Length from lens mount [1,2]||88mm (3.5 in.)|
|Overall length [1,3]||96.4mm (3.8 in.)|
|Maximum diameter||74.4mm (2.9 in.)|
|Weight ||450g (15.9oz)|
|Minimum aperture||f/22 (18mm) to f/40 (270mm)|
|Standard accessory||Flower-shaped Lens Hood|
|Mounts available||Nikon, Canon, Sony|