Large aperature wide-angle lens offering the best optical preformance in its category FLD, SLD and Aspherical lens elements.Filter Size (mm)-φ77㎜ Super Multi-Layer lens coating reduces flare and ghosting. Minimum focusing distance - 25 cm / 9.8 inch Angle of View (35mm) : 84.1°. Includes fast and near silent HSM autofocus, Compatible with Sigma USB Dock In order to avoid any malfunction problem, please operate one USB Dock per computer