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.
XLDExtra Low Dispersion
Dispersive properties even lower than LD elements
Extra Low Dispersion lens elements are made from a special high-grade glass that has dispersive properties (i.e. where refraction causes the dispersion of white light into spectral hues) even lower than standard LD lenses, in fact being similar to those of fluorite. In combination with LD elements, these make for an optimal optical design that delivers superb resolution with advanced correction of axial chromatic and magnification aberrations – major inhibitors of image quality.
The result is a lens that delivers sharp contrast and better descriptive performance throughout the entire zoom range.
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.
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.
Ultrasonic Silent Drive
'Travelling waves' generate a fast, smooth AF movement
This extremely quiet motor is ideal for photography of events, weddings, theatre or musical performances, as well as crucial moments on the golf course – any situation where autofocus noise is obtrusive. Major improvements in autofocus response and tracking ability over standard DC motors make for instantaneous focusing and spontaneous shooting of rapidly moving subjects.
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 is a material 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 produce simple motion into energy known as ‘deflective travelling waves’, which move around the circumference of the ring. The friction between these deflective travelling waves created on the metallic surface of the stator and the surface of the rotor produces force, causing the rotor to rotate. Attached to the rotor is the focusing lens, which is given a fast, smooth autofocus movement.
Moisture resistance adds protection
Moisture-resistant body construction helps prevent water from penetrating the lens, making it well suited ideal for travel and shooting outdoors.
Full-time manual focus
Fine focus adjustments using manual focus can be made during autofocus shooting, without the need to change focus mode.
|Angle of view (diagonal)||34°21′-12°21′ (with full-size SLR cameras)
22°33′-7°59′ (with APS-C sized sensor digital SLR cameras)
|Lens construction||23 elements in 17 groups|
|Minimum focus distance||1.3m (51.2 in)|
|Maximum magnification ratio||1:8 (at f=200mm:MFD 1.3m)|
|Length**||188.3mm (7.4 in)|
|Overall length***||196.7mm (7.7 in)|
|Weight*||1470g (51.9 oz) (including detachable tripod mount)|
|Diaphragm blades||9 (rounded diaphragm)****|
|Standard accessory||Flower-shaped lens hood|
|Mounts available||Canon, Nikon, Sony*****|