SP AF17-50mm F/2.8 XR Di II LD
The focal length is equivalent to 26-78mm when converted to a 35mm format. In particular, the 17mm focal length (26mm equivalent) provides a wider angle of view than ordinary standard zooms, while maintaining the lightweight and compact size.
The minimum focus distance of 0.27m over the entire zoom range achieves a maximum magnification ratio of 1:4.5 at 50mm. The lens boasts one of the best close-up shooting performances in the class of fast standard zoom lenses designed exclusively for digital cameras and featuring an f/2.8 maximum aperture throughout the entire zoom range.
Lightweight, compact fast standard zoom designed exclusively for digital SLRs, with 17mm wide-angle coverage
Exclusive design for digital SLR cameras achieves a fast standard zoom lens that covers virtually the same angles as focal lengths of 26-78mm when converted to a 35mm format. The wide-angle focal length is established at 17mm (26mm equivalent) to obtain a wider angle of view than ordinary standard zoom lenses.
Complicated mechanisms are built into this compact profile for excellent portability and ease of use. A complex triple-cam structure, where cams zoom and focus within a three-layer lens barrel, improves AF focus precision for close-up shots and control of torque when zooming. A comprehensive engineering overhaul has downsized its parts and increased their precision and durability, making the body lightweight and compact with a filter diameter of 67mm, overall length of 81.7mm (3.2”)*, and weight of 434g (15.3oz.)*.
* Values given are for Nikon AF cameras.
Special glass, and is optimisation for digital SLRs enhances optical quality in a compact design
The use of XR (Extra Refractive Index) glass in an innovative way optimises the overall distribution of optical power, and also reduces various aberrations to the absolute minimum while achieving remarkable compactness. In addition, suitable positioning of two hybrid aspherical elements serves to maintain imaging performance and to shorten and compress the entire optical system. Furthermore, an LD (Low Dispersion) glass element is used to accomplish effective compensation of on-axis and lateral chromatic aberrations, a critical factor for enhancing optical quality in digital photography, in order to achieve outstanding optical performance over the entire zoom range.
Revolutionary minimum focus distance of 27cm over the entire zoom range provides a 1:4.5 macro capability
The lens achieves a minimum focus distance of 27 cm (10.6”) over the entire zoom range, the best in its class among fast standard zoom lenses with an F/2.8 maximum aperture throughout the entire zoom range used exclusively for digital SLR cameras with APS-C sized image sensors. The maximum magnification ratio of 1:4.5  at the 50mm setting is the top level in its class.
Optical design dedicated to digital SLRs optimises the angle of incidence of light rays reaching the image sensor
This zoom lens uses an 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 by considering the variances during zooming.
Enhanced peripheral illumination
Peripheral light fall-off is minimised when compared with that of conventional lenses for film cameras, so 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 resolution, contrast and flatness of image field.
By employing internal surface coatings (i.e., multiple-layer coatings on cemented surfaces of plural elements) and new multiple-layer coating technology on ordinary elements, ghosting and flare due to the reflections that occur when light enters through the front element and reflections caused by the image sensors themselves are reduced to the absolute minimum.
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.
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.
 As of 15th December 2005. Based upon Tamron research of lenses in the same class.
As APS-C sized image sensors are smaller than 35mm film, the 17-50mm can fill the frame with almost the same scope as a lens with a maximum magnification ratio of 1:3.0 on a 35mm SLR camera.
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.
Super Performance series
Performance takes priority for superb image quality
This line of ultra-high-performance lenses is designed and manufactured to the exacting specifications demanded by professionals and others who require the highest possible image quality. The foremost priority is achieving superior performance parameters – high design standards take priority over cost constraints. As a result, Tamron SP lenses feature innovative designs that have established an enviable reputation for excellence amongst demanding photographers.
*Values given are for Nikon mounts.
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
New classifications for Nikon mounts
Tamron’s Nikon-mount lenses featuring an internal AF have until now been designated ‘N II’. Lenses using a coupler system* without an internal AF motor were designated as ‘N’. As future lens introductions for Nikon will have the internal AF motor as a standard feature, Tamron has simplfiied the designation of all Nikon-mount lenses as ‘N’, eliminating the ‘N II’ designation for future models. This change was effective from the 18-270mm F/3.5-6.3 Di II VC PZD (Model B008).
The ‘N’-classified lenses with coupler systems are:
- AF55-200mm F/4-5.6 Di II (Model A15)
- AF28-300mm F/3.5-6.3 XR Di (Model A061)
- SP AF200-500mm F/5.6-6.3 Di (Model A08)
- SP AF180mm F/3.5 Di (Model B01)
* Coupler systems use a shaft which connects with the AF motor built into the camera body to operate the lens.