From the Manufacturer
The SP AF17-50mm F/2.8 is a lightweight, compact, fast standard zoom lens designed exclusively for digital SLR cameras, expanding the product concept of the popular SP AF28-75mm F/2.8 zoom lens. In addition, portrait shots are made beautiful with the natural out-of-focus effect characteristic provided by the fast F/2.8 aperture. Additionally, a broader photographic expression through the use of faster shutter speeds as a result of the maximum aperture offers enhanced photographic pleasure. 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, to ensure stress-free photographic shots at all focal lengths and distances.
AF18-200mm F/3.5-6.3 XR Di II Highlights Di II
|Extraordinary detail at the macro level |
Lenses are designed for exclusive use on digital cameras with smaller-size imagers and inherit all of the benefits of our Di products. These lenses are not designed for conventional cameras and digital cameras with image sensors larger than 24mm x 16mm. Extra Refractive Index Glass (XR)
Extra Refractive Index (XR) glass can bend light rays at steeper angles, thereby decreasing the physical length of the lens while enhancing imaging performance by minimizing optical aberrations. This has allowed Tamron to develop a line of shorter, smaller-diameter, lighter lenses without sacrificing lens speed, and actually upgrading image quality compared to older designs. XR glass is costlier than conventional glass but it yields enhanced optical power distribution, making possible many of the outstanding and innovative lens designs that bear the XR designation. XR glass, with its superior light-bending power, 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 by hand.
Low Dispersion (LD)
|Special glass for better performance and more compact lens designs |
Low dispersion (LD) glass elements in a lens help reduce chromatic aberration; the tendency of light of different colors to come to different points of focus at the image plane. Chromatic aberration reduces the sharpness of an image, but glass with an extremely lowdispersion index, has less of a tendency to separate (defract) a ray of light into a rainbow of colors. This characteristic allows the lens designer to effectively compensate for chromatic aberration at the center of the field (on axis), a particular problem at long focal lengths (the telephoto end of the zoom range), and for lateral chromatic aberration (towards the edges of the field) that often occurs at short focal lengths (the wide-angle end of the zoom range.)
Super Performance (SP) for Discriminating Shooters
|Low Dispersion (LD) Glass for Greater Lens Sharpness |
Tamron SP (Super Performance) series is a line of ultra-high-performance lenses designed and manufactured to the exacting specifications demanded by professionals and others who require the highest possible image quality. In creating SP lenses Tamron’s optical designers put their foremost priority on achieving superior performance parameters—they are all designed to a higher standard with little regard for cost constraints. As a result, Tamron lenses bearing the SP designation feature impressive and innovative designs that have established an enviable reputation for excellence among those knowledgeable photographers that demand the very best. Zoom Lock (ZL)
Another original Tamron mechanical engineering concept is the Zoom Lock (ZL), a simple convenience feature that prevents undesired extension of the lens barrel when carrying the camera/lens unit on a neck strap.
The Tamron SP AF17-50mm f/2.8 XR Di II LD Aspherical [IF] is a lightweight, compact, fast standard zoom lens designed exclusively for digital SLR cameras. The focal length of this lens is equivalent to approx. 26-78mm in 35mm format. This lens offers an f/2.8 maximum aperture throughout the entire zoom range, to ensure stress-free photographic shots at all focal lengths and distances. Additionally, a broader photographic expression through the use of faster shutter speeds as a result of the maximum aperture offers enhanced photographic pleasure. FEATURES: Optimized for Digital SLR - The use of XR (Extra Refractive Index) glass optimizes 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. LD Glass - 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. Enhanced Peripheral Illumination - Peripheral light fall-off is minimized when compared with that of conventional lenses for film cameras, so images are uniformly bright from the center to the periphery. Internal Surface Coating to Reduce Ghosting and Flare - By employing "Internal Surface Coatings" (i.e., multiple-layer coatings on cemented surfaces of plural elements) and multiple-layer coating technology on ordinary elements, ghosting and flare due to the reflections that occur when light enters through the front element and