The 12-28mm f/4.0 AT-X Pro APS-C lens for Canon from Tokina is a wide-angle to standard length zoom lens with a maximum aperture of f/4.0. It is compatible with Canon APS-C cameras and provides a 35mm focal length equivalency of 19-45mm. This compact lens features a one-touch AF/MF clutch operation to switch back and forth between auto and manual focus, for manual focus slide the focus ring back and for autofocus allow to the ring to rest in the forward position. A newly designed GMR (magnetic precision) AF sensor is mounted close to the AF motor and provides fast, accurate AF. The lens' Sd-m (silent Drive-Module) means that autofocus responds smoothly and silently, which is ideal when shooting HD video. The use of SD glass (ultra-low dispersion glass), which emulate fluorite glass in performance, aims to eliminate chromatic aberration and aspherical lens elements in both the front and rear lens groups correct distortion and also helps to minimize aberrations for sharp imaging throughout the zoom range.