The optical design of the Sigma AF 28-70mm f/2.8 DG DN is based on the 24-70mm F2.8 DG DN Art, which is renowned for its outstanding optical performance throughout its zoom range. True to the Contemporary line's core concept, the 28-70mm F2.8 DG DN Contemporary was developed to offer the right balance of performance and portability, and as such, this large-aperture standard zoom delivers outstanding image quality that rivals Art line lenses in a body light enough for day-to-day use. Building on state-of-the-art technology, the 28-70mm F2.8 DG DN Contemporary has an advanced optical design that includes three aspherical, two FLD, and two SLD elements. In short, the Sigma 28-70mm F2.8 DG DN Contemporary combines all of the key optical features required of a large-aperture standard zoom lens, which are essential for photographing a wide variety of subjects in a range of shooting conditions.