This lens has a manual focus ring with and interlocking follow focus gear to allow to be used in a cinema follow focus system.
This lens is for shooting video with DSLR (VDSJR) cameras. To use follow focus, the manual focus ring is placed in the MF position before shooting. At the time of the normal photography, you can use autofocus.
Tokina’s exclusive One-touch Focus Clutch Mechanism allows the photographer to switch between AF and MF simply by snapping the focus ring forward for AF and back toward the lens mount for manual focusing. The lens is also designed to stand up to the rigors of daily use by photographers in a wide variety of shooting conditions and environments.
The Tokina AT-X 17-35 PRO FX is a compact wide-angle zoom lens for full size cameras. In Cine/Video use it demonstrates it’s preeminent power.