The optical design of this lens uses a high-performance XLD (Extra Low Dispersion) element, which is manufactured out of a special glass with an extremely low refractive index. The refractive index describes the ability of the lens to split a light beam into its spectral colours. The dispersive properties are even lower than standard LD lenses and are at a level similar to fluorite. The XLD lens in combination with the LD element delivers the highest contrast and brilliance. This effectively prevents the problem of chromatic aberration in telephoto photography and delivers a high level of sharpness even in the peripheral regions. The result is a lens that effectively compensates for axial chromatic aberration and magnification aberration throughout the entire zoom range and guarantees the highest resolution and brilliance for your pictures.