The Sigma 18-35mm f/1.8 DC HSM is an Art-series zoom, covering wide-angle to normal focal lengths. Separating itself from the pack, this zoom features an exceedingly bright f/1.8 constant maximum aperture, which suits its use in difficult lighting conditions and offers impressive depth of field control throughout the zoom range. The optical design incorporates a series of SLD and aspherical elements, which help to achieve high clarity and sharpness by suppressing various aberrations, color fringing, and distortion.