As a G Master lenses, optical performance is prioritized and they emphasize both sharpness and bokeh quality for versatility regardless of subject distance or aperture setting.
Two XA (extreme aspherical) elements, along with one standard aspherical element, promote high sharpness throughout the aperture range, even when working at the bright f/1.8 position. Aspherical elements feature superior surface precision for effective control over astigmatism, field curvature, coma, distortion and other spherical aberrations for highly accurate rendering and low distortion. 

The combination of several aspherical elements, along with sophisticated focusing motors, promotes a truly compact and lightweight design, especially for such an ultra-wide focal length. One Super ED element and two extra-low dispersion elements are featured in the lens design and help to reduce chromatic aberrations and color fringing for improved clarity and color neutrality. 

Nano AR Coating II has been applied to reduce surface reflections, flare, and ghosting for increased contrast and color rendering in strong lighting conditions. This updated coating is better suited for larger, curved elements and is especially adept at minimizing internal reflections.