Nikon AF-S DX NIKKOR 17-55mm f/2.8G IF-ED Zoom Lens Short Description Fast, ultra-wideangle zoom lens with Silent Wave Motor Three ED (Extra-low Dispersion) glass elements minimize chromatic aberration, provide higher resolution and superior contrast Three aspherical lens elements minimize distortion, especially at the periphery, for superior optical performance 'SWM' (Silent Wave Motor) for swift autofocusing with superior accuracy and ultra-quiet operation The rounded diaphragm opening (7 blades) makes out-of-focus elements appear more natural M/A mode allows rapid switching between autofocus and manual even during AF servo operation, with virtually no time lag Internal Focusing (IF) design for smoother focusing and great body balance