This Sigma 17mm f/4 DG DN Contemporary Lens is an ultra-wide-angle prime for Sony E-mount cameras. Designed with an inner focusing system and stepping motor, this lens provides fast and reliable autofocus for both stills and video. The optical design produces high sharpness and clarity throughout the aperture range, and individual elements feature a super multilayered coating to suppress flare and ghosting for greater contrast and color fidelity when working in strong lighting conditions. A compact, ultra-wide prime lens designed for full-frame Sony E-mount mirrorless cameras that can also be used on APS-C models where it provides a 25.5mm equivalent focal length. Equipped with an aperture ring, focus mode switch, and a knurled manual focus ring for a pleasing tactile experience. Compatible with AF assist function and lens aberration correction on supported cameras.