A high performance telephoto lens. This is the world’s first lens for interchangeable-lens cameras targeting ordinary consumers, which used artificial crystal fluorite (calcium fluoride/CaF2) lens elements to achieve extremely high contrast correcting chromatic aberration, which is destiny of super telephoto lenses. Fluorite has a crystalline structure and is equipped with extraordinary optical characteristics unobtainable with optical glass – a low index of refraction and low dispersion. It used two fluorite elements. Moreover, the dispersion characteristics of fluorite are nearly identical with optical glass for wavelengths in the range from red to green, but differ greatly for wavelengths in the range from green through blue. Those characteristics enable significantly improve the imaging performance of super-telephoto lenses. “F” in the name stands for “Fluorite”.