Sigma 17-50mm f/2.8 EX DC OS HSM FLD Large Aperture Standard Zoom Lens for Nikon Digital DSLR Camera Type: Zoom Lens Focal Length: 50 mm Camera Mount: Nikon F Aperture: Maximum: f/2 Minimum: f/22 Compatibility: Nikon Diameter: 77 mm Focus Type: Auto Focus Magnification: 0.20x