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.
Di-II lenses cannot be used with digital SLR cameras using image sensors that are larger than that of an APS-C size imager (e.g. 1D series), or with 35mm film SLR cameras.
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.
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.
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.
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 reflections caused by the imagers themselves are reduced to the absolute minimum.
The Zoom Lock prevents unwanted barrel extension when carrying the lens/camera combination.