The Tokina 12-28mm f/4 AT-X Pro DX is a wide-angle zoom lens specifically designed for Canon crop-frame DSLRs. Key features include:

Wide-Angle Zoom. With a 35mm-equivalent focal length of 19-45mm, it’s a great choice for landscape/cityscape shooters who want a zoom lens that covers wide to normal range. The f/4 aperture throughout the zoom range helps when hand-holding in moderately low light.

Autofocus/Manual-Focus Clutch. This quick, one-touch operation allows for simple switching between autofocus and manual focus. A GMR (magnetic precision) sensor improves autofocus speed over previous Tokina lenses, and a SD-M (Silent Drive-Module) minimizes audible noise during autofocusing making it even better for video use.