The Tokina 14-20mm f/2 AT-X PRO DX, Canon EF-S Fit is an new wide angle lens for APS-C sized (cropped) sensors. Super-fast F2 aperture, the fastest lens ever made by Tokina, provides 21 to 30mm focal length in 35mm equivalency. The 14-20mm F2 has an all-new proprietary optical design that uses three aspherical lens elements (2 all-glass molded and 1 hybrid) to achieve superior contrast, sharpness, and correct for spherical aberrations. Additionally, Tokina uses of an four SD (Super-low Dispersion) glass elements to control chromatic aberrations. The super-bright, constant F2.0 aperture of the Tokina 14-20mm makes viewing, auto focus and shooting possible in very low light situations while still maintaining reasonable size and weight. Furthermore the One-Touch Focus Clutch Mechanism allows the photographer to switch between AF and MF with ease. The advanced features and Tokina's normal, superior build it make it a must have lens for many photographers.