21mm F1.4 high speed wide-angle lens. Focus is achieved without any lengthening or rotation of the front lens element. A Large aperture lens design that gathers more light for superior low light results and enables shallow depth of field imaging. Low Chromatic Aberration: All colors to come into focus in exactly the same place for reduced color fringing and increased sharpness. Helps prevent haze, lack of contrast and artifacts scattered throughout the image from bright source(s) of light. Helps prevent a blur that looks like a comet's tail that can occur at a lens edge.