This extreme wide-angle is specially developed for cameras with an APS-C size sensor. With a maximum aperture opening of f/2.8, the lens is also usable in situations with less light. This large opening also ensures a soft background gradient. Tokina has a special system, named "One-touch Focus Clutch". This is a ring which allows you to very quickly switch from auto to manual focus without touching the camera. To reduce unwanted image distortions, the lens has SLD and aspherical lens elements.