AF18-200mm F/3.5-6.3 XR Di II
Advanced Tamron technology – special XR and LD glass, hybrid aspherics, and internal focusing – is what makes all this possible in a dramatically downsized package. Cutting-edge internal and external multi-coating assures flare-free pictures even under challenging conditions. With specs like this, no wonder it's Tamron's most popular lens.
Dedicated for digital SLR cameras
By incorporating an optical design for exclusive use with digital SLR cameras with smaller-size imagers, this high-power zoom lens provides the same focal length, when converted to a 35mm format, equivalent to Tamron’s 28-300mm. Therefore, you can meet virtually every photographic opportunity with this single zoom lens without changing lenses. When paired with a wideangle zoom, you can thoroughly enjoy digital SLR photography with a combined equivalent focal length coverage of 27-300mm.
Optical system uses special glass and is optimised for digital SLRs to enhance optical quality in a compact design
The new AF18-200mm high power zoom lens from Tamron features an entirely new optical design using XR (Extra Refractive Index) glass in an innovative way in order to optimize the overall distribution of optical power throughout the entire zoom range. This design reduces various aberrations to the absolute minimum and achieves remarkable downsizing at the same time. In addition, three hybrid aspherical lens elements and two LD (Low Dispersion) glass elements are used to accomplish effective compensation of on-axis and lateral chromatic aberrations, a critical factor to enhance the optical quality in digital photography. As a result, this lens is truly multi-purpose but still provides outstanding image quality.
Optically dedicated to digital SLRs by optimising the angles of light rays reaching the image sensor
The zoom lens uses a new optical system designed to confine the changing angles of incidences of light rays reaching the imager within a certain scope over the entire image field from the center to the periphery, by considering the effects of variances due to zooming.
Enhanced peripheral illumination
Peripheral light fall-off is minimised when compared with that of conventional lenses for film cameras so that images are uniformly bright from the centre to the periphery.
Since the lens is designed exclusively for digital SLR photography, it provides high image quality in terms of resolution, contrast and flatness of image field.
Internal surface coating to reduce ghosting and flare
Ghosting and flare caused by aberrations are annoying factors in digital SLR photography, so Tamron has adopted various countermeasures against the problem including the employment of internal surface coatings (i.e., multiple-layer coatings on cemented surfaces of plural elements) and new multiple-layer coating technology on ordinary elements in order to minimise reflections that occur when light enters through the front element and to reduce image degrading effects caused by the imaging sensors themselves.
Revolutionary minimum focus distance – 0.45m (17.7″) for 1:3.7* macro capability
It is an important condition for a multi-purpose zoom lens to provide the capability of getting close to the subject. The new 18-200mm zoom lens realises an MFD (Minimum Focus Distance) of 0.45m (17.7″) through the employment of a new optical/mechanical design configuration. Since the maximum magnification ratio at 200mm is 1:3.7*, you can enjoy close-up photography easily and conveniently.
* The Maximum Magnification Ratio of this lens is 1:3.7 while the Maximum Magnification Ratio of the AF28-300mm (Model A061) is 1:2.9. However, the 18-200mm can fill the frame with almost the same scope as the A061 does when shooting with a 35mm SLR camera, since the new lens is exclusively designed for digital SLR cameras with smaller-size imagers. The Maximum Magnification Ratio of 1:3.7 is equivalent to 1:2.8 when converted to 35mm film format.
High power, yet compact and lightweight thanks to newly developed mechanisms
New and complex mechanisms are hidden in this lens’ compact construction. Several engineering innovations were required to downsize the design, produce high-precision parts and increase durability, imbuing this multi-purpose zoom lens with excellent portability and ease of use.
Flower-shaped hood is supplied with the lens to shield stray light
Included as a standard accessory, the flower-shaped hood matches the rectangular shape of the image sensor to most effectively block the interference of superfluous light rays entering from outside the borders of the image area, helping to ensure sharp, clear, flare-free images with crisp detail in the shadow areas.
Useful when carrying the lens/camera over the shoulder
Another original Tamron mechanical engineering concept is the zoom-lock mechanism, which prevents the weight of the lens barrel from extending the lens when carried on the camera pointing downward. This eliminates the danger of accidentally knocking the lens while walking around and enhances responsiveness in the field. Simply zoom the lens out to its widest focal length and use the sliding zoom-lock switch to lock the barrel in place.
New external design on the Di-II series conveys “high-performance, high-precision” image
Improvements have been made to the external design by adding a gold-coloured band between the focus and zoom rings to enhance the appearance and make it stand out as a Di-II lens. The rubber patterns of the zoom and focus control rings have been improved at the same time to complement the digital camera design style and to provide better handling.
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.
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.
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.
Focusing elements inside the optical design make for better handling
In many lenses, the front elements move back and forth to alter the focus distance. With an internal focusing (IF) mechanism, the focusing elements are inside the optical design. Because the front lens elements remain static, the lens’ actual length does not change. This provides several benefits both to the image and during photography:
- The barrel is not subject to stray light entering from external helicoids that can adversely affect image quality
- A non-rotating front filter thread makes it easier to use filters such as graduated filters and polarisers
- A flower-shaped lens hood will remain in the correct position to most effectively shield the lens from stray light
- Better balance and more predictable handling because the lens length does not change during focusing
- Generally, a much closer minimum focusing distance throughout the zoom range
- Improved optical performance by minimising loss of illumination at the corners of the image field (vignetting)
- Suppression of other aberrations that become more troublesome at different focusing positions.
Integrated focus cam optimises internal focusing
Tamron’s Integrated Focus Cam is a precision mechanical component that optimises the co-ordinated movement of the Internal Focusing (IF) system with the Multiple Cam Zoom Mechanism. This ingenious mechanism ensures accurate and seamless positioning of all the internal elements within the lens and coordinates them with the external zoom and focus controls.
* Values given are for the Nikon-mount model.
Di II lenses are designed for exclusive use on digital SLR cameras with APS-C-format image sensors. This kind of sensor has dimensions smaller than that of a frame of 35mm film, so the circle of light transmitted by the lens to the sensor can be smaller. This means that the lens too can be more compact in size and often lighter in weight.
All Tamron Di II lenses are specially optimised to meet the performance characteristics of DSLRs, providing maximal resolution concentrated within the image field and assuring that light rays at the edges of the frame reach the sensor at favourable angles, thereby minimising peripheral light falloff.
As well, Di II lenses incorporate measures to increase light transmission and eliminate the ghosting and flare that are particularly noticeable with digital cameras. Tamron’s advanced multi-coatings are applied not only to external and internal lens surfaces, but also to surfaces in between cemented lens elements.
Tamron’s Di-II range