The Tokina 16-50mm f/2.8 AT-X 165 PRO DX Autofocus Lens is a large-aperture everyday zoom lens designed exclusively for use with digital SLR cameras that feature the smaller APS-C size sensor. It features a fast constant aperture of f/2.8, and provides a focal length equivalent to 24-75mm in 35mm format. Ideal for outdoor scenery, portraits, or photojournalism photography. The lens features SD glass lens elements to correct for chromatic aberrations and focuses all colors accurately at the film plane. DX series lenses feature a smaller image circle (rear of lens) and are designed to match the smaller dimensions used for the image sensor on some digital cameras. As a result, these lenses are also more compact and lightweight, and are better matched to digital SLR cameras. This Lens is Not compatible with 35mm film or full-size chip digital cameras.