The sigma 18 35mm f18 dc hsm lens is the first wide angle zoom lens as of 22nd april 2013 to achieve a maximum aperture of f18 throughout the entire zoom range the sigma 18 35mm is a standard zoom lens that offers a focal range equivalent to 27 525mm in the 35m format the 9 blade rounded diaphragm creates an attractive round bokeh at large aperture settings while the hsm hyper sonic motor ensures a silent high speed af this lens incorporates a wide glass molded aspherical lens with s