The Canon FD 20mm f/2.8 S.S.C. lens is an ultra-wide-angle prime lens designed for the Japanese manufacturer's manual reflex system, featuring a diagonal angle of view of 94 degrees. The optical design utilizes a configuration of nine elements in nine groups, incorporating a floating lens system for aberration compensation at close distances, known as the Floating System, which ensures high sharpness across the entire frame even at the minimum focusing distance of 25 centimeters. The Super Spectra Coating multilayer anti-reflective treatment, identified by the S.S.C. acronym, is applied to optimize light transmission and effectively reduce internal reflections and ghosting while maintaining neutral color balance. The mechanical construction is entirely metallic with a Breech Lock mount, a solution that ensures a rigid and precise connection between the lens and the camera body without friction on the contact surfaces. The six-blade diaphragm provides accurate control of depth of field from f/2.8 down to f/22, while the 72mm front filter diameter allows for the use of standard accessories without incurring excessive vignetting.