This Sigma 10-20mm lenses features a constant f3.5 aperture resulting in the ability to shoot in low light and still create sharp pictures. The ultra-wide focal length is always popular for landscapes, room interiors, group shots & more. With two ELD glass elements and one SLD glass element aiding to create images free from aberrations, flare and ghosting, the Sigma 10-20mm is a superb wide angle zoom lens at a great price.