Di: Digitally Integrated Design, is a designation Tamron puts on lenses featuring optical systems designed to meet the performance characteristics of digital SLR cameras. Advent of an ideal Ultra wide-angle zoom lens well balanced in all aspects. With its superb image quality, compact size and excellent operational ease, this ultra wide-angle zoom lens lets you enjoy dynamic image composition by exaggerating your main subject against a wide background. Tamron's new ultra wide-angle zoom lens starts at 17mm when used with a conventional 35mm SLR camera. When mounted on an APS-size digital SLR camera, it provides a focal length coverage equivalent to a 28-55mm (on a 35mm format camera), covering the desirable wide-angle to standard range.