Sigma’s Nano Porous Coating is a lens coating that is designed to make a lens less susceptible to strong incident light, such as backlight. It uses porous silica, which has nano-sized holes containing air, as the coating material. Having holes of this size enables a large reduction in the refractive index, allowing the reflectance to be lowered more than conventional anti-reflective coatings. As a result, reflected light causing flares and ghosting is sharply reduced, yielding clearer, higher contrast images.