SP AF 70-200mm F/2.8 Di Features
While overall dimensions are confined to the absolute minimum, the new SP AF70-200mm F/2.8 zoom lens is packed with features that allow stress-free photography: a versatile MFD of just 37.4" over the entire zoom range; best-in-class maximum macro magnification ratio of 1:3.1 at f=200mm; and an advantageous internal focusing (IF) system. The new tele-zoom lens covers a desirable focal length range of 70mm medium telephoto to 200mm telephoto when mounted on full-size format SLR cameras and a focal length range from 109mm to 310mm ultra telephoto when mounted on a DSLR camera with an APS-C sized imager.
Digitally Integrated (DI) Lenses for Top Imaging Performance
Di (Digitally Integrated Design) is a Tamron designation that applies to lenses that have been optimized for digital capture using advanced multi-coating techniques and optical designs that assure excellent image quality across the entire picture field. Because of these characteristics, Di lenses provide outstanding performance on cameras with full-frame and APS-C format sensors as well as on 35mm film.
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
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.
Internal Focusing (IF) System
Internal focusing provides numerous practical benefits to photographers including a non-rotating front filter ring that facilitates the positioning of polarizing and graduated filters, and more predictable handling because the lens length does not change during focusing. Even more important, Tamron's Internal Focusing (IF) system provides a much closer minimum focusing distance (MFD) throughout its entire focusing range. In addition, IF improves optical performance by minimizing illumination loss at the corners of the image field, and helps to suppress other aberrations that become more troublesome at different focusing positions.