The Sigma 50-100mm f/1.8 DC HSM is an Art-series zoom mixing impressive versatility with advanced optics. The bright f/1.8 constant maximum aperture offers consistent low-light performance throughout the zoom range and also affords greater control over focus placement for shallow depth of field and selective focus applications. The optical design incorporates a series of low dispersion and high-refractive index elements, which help to achieve high clarity and sharpness by suppressing various aberrations, color fringing, and distortion.