Optimized for speed, this lens is equipped with a fast and constant f/2.8 aperture that will be an asset in low-light conditions as well as for creating images with shallow depth of field. Bokeh is made even better by the implementation of an eleven-blade circular diaphragm for smooth out-of-focus areas. Also, there is a double-linear and ring Super Sonic wave Motor system that provides fast, responsive autofocus in both stills and video.