Sigma 15-30mm f/3.5-4.5 Ex Dg If Aspherical Ultra Wide Angle Zoom Lens for Canon Ultra wide-angle zoom lens designed for Canon digital SLR cameras 15-30mm focal length 3.5-4.5 maximum aperture Super Multi Coating reduces flare and ghosting that tends to occur when using digital SLR cameras 17 lens elements in 13 groups; aspherical elements at front and rear lens groups