Sigma Pro End 120-300 with a constant aperture of F2.8 This lens transforms a large-aperture F2.8 300mm lens into a zoom lens that allows you to determine the picture composition you want without having to change your vantage point. It has two SLD (the special low dispersion) glass elements in front group and another element of SLD is being used for rear group for excellent correction of chromatic aberration. New coating reduces Ghost and Flare - The new multi layer lens coating and lens design reduce flare and ghost, which is a common problem with digital cameras and also creates an optimum color balance through the entire zoom range. Hyper sonic motor - The AF drive for Sigma SA, Canon and Nikon cameras is equipped with a silent, responsive and high speed HSM , which also provides full-time manual focus function. Inner Focusing and Inner Zooming - Since focusing and zooming do not change its overall length, this lens is easy to hold and use. In addition, since the front of the lens does not rotate, a circular polarizing filter can be easily attached and use. Specifications - Lens Construction - 18 Elements in 16 Groups Angle of View - 20.4 -8.2 degrees Number of Diaphragm Blades - 9 Blades Minimum Aperture - F32 Minimum Focusing Distance - 150-250cm/59.1 in.-98.4 in. Maximum Magnification - 1:8.6 Filter Size - Diameter 105mm Dimensions - Diameter 112.8mm X Length 271mm 4.4 in. X 10.7 in. Weight - 2600g/91.7 oz.