Canon EF 50mm f/1.4 USM Standard & Medium Telephoto Lens for Canon SLR Cameras - Fixed International Version (No Warranty) 50mm standard lens with f/1.4 maximum aperture for Canon SLR cameras 2 high-refraction lens elements and Gaussian optics help eliminate astigmatism Delivers crisp images with little flare at the maximum aperture Extra-small Micro USM focus adjustment and full-time manual focusing Measures 2.9 inches in diameter and 2 inches long