Designed for full frame DSLR cameras, the Tokina atx-i 17-35 mm F4 FF give photographers a new wide-angle option that covers the majority of landscape scenes. With a focal length of 17 mm at the wide side, the lens yields a spectacular 103.9 degree field of view which is great for shooting landscapes, street snap, architecture, time-lapse. The Tokina atx-i 17-35 mm F4 FF offers constant f/4 aperture, robust design while still maintaining a reasonable size and weight that is especially important for active travel. Optical performance two super-low dispersion glass elements and 3 aspherical glass elements allow the lens to achieve excellent contrast and sharpness as well as control chromatic aberrations. Lens construction MTF chart atxi_1735_mtf_17 atxi_1735_mtf_35 Tokina atx-i 17-35 mm F4 FF has good sharpness and no distortion, which are important for architecture. Accurate and fast AF Precise Auto Focusing is actuated by combination of Tokina GMR sensor and SD-M (Silent Drive Module). One-Touch Focus Clutch 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. Moisture protection Additionally the mount area is sealed around making the lens more resistant to moisture and to stand up to the rigors of daily use in a wide variety of shooting conditions and environments.