Sigma 18-35mm f/1.8 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 an 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. A Super Multi-Layer Coating has also been applied, too, which controls lens flare and ghosting for improved contrast and color accuracy. Balancing the optical merits, this 18-35mm also sports an advanced Hyper Sonic Motor, along with an internal focusing design, to promote fast, quiet, and precise autofocus performance.