As a leading manufacturer of lenses, Sigma is continually innovative in the use of new materials and lens designs. The new FLD glass is the highest level of low dispersion glass available, offering extremely high light transmission. It offers performance equal to fluorite glass, which has a low refractive index and low dispersion compared to current optical glass. It also benefits from high anomalous dispersion. Using these characteristics gives excellent correction for residual chromatic aberration (secondary spectrum), which cannot be corrected by ordinary optical glass, and ensures high-definition, high-contrast images. And because the density of FLD glass is lower than traditional optical glass, it allows a lighter construction of large aperture lenses.
FLD glass offers superior optical performance at an affordable price and can be found in some of Sigma’s recently announced lenses; four elements have been used in the Sigma 8-16mm F4.5-5.6 DC HSM, and two elements in both the Sigma APO 70-200mm F2.8 EX DG OS HSM and the Sigma 17-50mm F2.8 EX DC OS HSM.