The Tamron AF18-200mm F/3.5-6.3 XR Di-II LD Aspherical (IF) MACRO is a high power zoom lens designed for exclusive use with digital SLR cameras using smaller-size imagers. 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.
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, the lens provides outstanding optical quality in a multi-purpose zoom lens.
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" and new multiple-layer coating technology on ordinary elements in order to minimize reflections that occur when light enters through the front element and to reduce image degrading effects caused by the imagers themselves.
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 realizes 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 f=200mm is 1:3.7, you can enjoy close-up photography easily and conveniently.
The Zoom Lock prevents unwanted barrel extension when carrying the lens/camera combination. Improvements have been made to the external design by adding a gold-colored 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 compliment the digital camera design style and to provide better handling.