The Canon EF 16-35mm f/4L IS USM Lens is a wide-angle zoom lens featuring a constant f/4 maximum aperture to provide consistent performance throughout the zoom range. The optical design incorporates three aspherical elements, including one large-diameter aspherical element, as well as two UD (Ultra-low Dispersion) elements to minimize chromatic aberrations and contribute to high edge-to-edge sharpness and resolution. A fluorine coating has also been applied to the front and rear lens surfaces to reduce flare and ghosting for maintained color neutrality and image contrast.