The large angle of view of the Sigma 12-24mm f/4.5-5.6 EX DG ASPH Zoom (122 degree super wide angle of view at 12mm along the diagonal axis) is ideal for shooting indoors as well as landscape photography. It has a variable angle of view from 122 degrees to 84.1 degrees. Four Special Low Dispertion (SLD) glass elements are provided for effective compensation of color aberration, which is a common problem with super-wide angle lenses. Two pieces of glass mold and one-piece hybrid aspherical lenses offer excellent correction for distortion as well as all types of aberration. By effective arrangement of lens elements and advanced technology, this lens has super compact dimensions of 100mm full-length and 87mm maximum diameter. It is equipped with an Inner Focusing System that will keep the length of the lens unchanged while controlling aberration. Features: First zoom lens that has 122 degree diagonal angle of view at 12mm focal length Variable angle of view from 122 degrees to 84.1 degrees Equipped with 4 piece SLD glass elements and 3 piece aspherical lenses producing a high level of optical performance Inner Focusing System insures the length of the lens remains unchanged whilst controlling aberration Minimum focusing distance of 28cm at all focal lengths. EX DG Series - the ideal lens for digital SLR cameras Lens Technology Explained: ASP (Aspherical Lens)The aspherical lens complex allows freedom of design, improved performance, a reduced number of component lenses and a ...