Sigma 24mm f/1.8 EX DG Aspherical Macro Large Aperture Wide Angle Lens for Nikon SLR Cameras Designed for use with full frame digital cameras. May also be used with smaller APS-c size sensors with a corresponding effective increase in focal length to about 35mm with most cameras Two Aspherical glass elements offer correction for distortion Floating internal focus system enables a minimum shooting distance of 7.1 inches Dual Focus system allows for easy manual override of the autofocus when difficult subjects are encountered 9 Blade diaphragm provides pleasant out of focus highlights