The tokina 14 20mm f2 at x pro dx is a wide angle zoom lens with super fast f2 aperture designed for canon dslrs with an aps c sensor its bright f20 aperture makes viewing autofocus and shooting in low light situations possible while still maintaining a compact size and weight its one touch focus clutch mechanism allows the photographer to switch between af and mf simply by snapping the focus ring forward and back the lens is also well built and able to stand up to the rigors of daily use