The Sigma 50-100mm f/1.8 DC HSM Art is a light-sensitive f/1.8 portrait lens for Canon single-lens reflex cameras. With a crop factor, 50-100mm zoom yields a range that corresponds to 75-150mm on a full-frame camera. The lens has a fixed aperture of f/1.8. This makes the lens not only suitable for portrait photography, but also ensures optimum performance in low-light situations. Are you planning to record? The zoom and focus ring controls are aligned so that the lens doesn't extend.