Sigma 12-24mm f/4 DG HSM is an Art-series zoom, characterized by its advanced design to greatly reduce distortion for a high degree of sharpness. A series of low dispersion and aspherical elements minimize both chromatic and spherical aberrations throughout the zoom range in order to achieve high clarity and color accuracy. A Super Multi-Layer Coating also helps to suppress lens flare and ghosting for color-accurate, contrast-rich imagery in a variety of lighting conditions. Equipped with a Hyper Sonic AF motor with an optimized algorithm for speed and accuracy. The lens also offers a large focusing ring with full-time manual override settings for quickly making adjustments. A rounded 9-blade diaphragm improves image quality by helping create smooth bokeh, and the lens is constructed from a lightweight and durable thermally-stable composite.