Canon EF 50mm f/1.4 USM Standard & Medium Telephoto Lens for Canon SLR Cameras - Fixed Standard focal length 50mm lens is effective in a multitude of shooting situations and ideal for day-to-day shooting Elements/Groups: 7/6; Diaphragm: Blades 8; Filter Thread: Font 58mm An f/1.4 maximum aperture provides clear imaging in low light situations and shallow depth of field Ultrasonic autofocus motor (USM) operation is fast, smooth and virtually silent Two high-refraction lens elements and new Gaussian optics eliminate astigmatism and suppress astigmatic difference Minimum focusing distance: 17.8 inch This large aperture standard prime lens has superior peripheral brightness even at the maximum aperture Lens construction: 8 elements in 6 groups, Filter size: 77mm Optimized for Digital  super multi-layer coating minimizes flare and ghosting  a common problem of digital cameras The optimum optical design and molded glass aspherical lens elements provide excellent correction for all types of aberrations, including coma aberration, resulting in superior optical performance The Hypersonic Motor (HSM) ensures silent, high speed auto-focusing as well as full time manual focusing capability