The Tamron 70-200mm f/2.8 Di LD (IF) Macro Lens is a telephoto zoom lens that has a large maximum aperture of f/2.8 which remains constant throughout the zoom range. It also offers an excellent close-focusing-distance minimum of just 3.1' (0.95 m) throughout its entire zoom range, with a maximum macro magnification ratio of 1:3.1 at f=200mm. When mounted on an APS-C sensor size digital SLR camera, it provides a focal length equivalent of 112-320mm. Di (Digitally Integrated Design) is a designation Tamron puts on lenses featuring optical systems designed to meet the performance characteristics of digital SLR cameras. Features like LD glass elements and Internal Focusing put this lens in the same category as the much bigger and more expensive professional Tamron lenses.