STM functionality provides quiet, smooth and continuous autofocus during video operation. The circular aperture formed by 7 diaphragm blades combined with the wide aperture can give you beautiful bokeh.
EF Mount Lens. Camera Mount Type Canon EF. Aspherical Lens Element. STM Stepping Motor for Smooth, Silent AF. Lens Coatings Reduce Ghost & Flare. STM Focus in Video on Select EOS Rebels. Focal Length 40mm.