from Canon, Blue spectrum refractive optics BR optics is based on a new organic optical material, developed by reexamining lens material from its molecular structure. This new lens material features unique anomalous dispersion characteristics that are capable of greatly refracting blue light (short wavelengths spectrum), which has traditionally been difficult to focus on a single point. Incorporation of a BR lens, consisting of BR optics sandwiched between concave and convex glass lenses, makes it possible to control the path of blue light (short wavelength spectrum), producing clear, sharp images by thoroughly reducing chromatic aberration. Nikon also introduced Nikkor z 400mm f/4.5 VR S telephoto lens with SR lens: The lens is constructed of 19 elements in 13 groups, including one Extra-low Dispersion (ED) element, two Super ED elements and one Short-wavelength Refractive (SR) lens element. The SR element refracts blue light more than green or red, helping to control longitudina...