Canon EF 20mm f/2.8 USM - Canon EF Mount

The Canon EF 20mm f/2.8 USM is a wide-angle prime lens designed for full-frame EF mount cameras. It features an Ultra Sonic Motor (USM) for fast, quiet autofocus and supports full-time manual focusing. The optical design includes an aspherical element to correct aberrations, providing good rectilinear performance for architecture and landscape work. Its relatively fast f/2.8 aperture makes it useful in lower light conditions compared to standard zoom lenses at similar focal lengths. On the used market, test the USM motor to ensure it locks focus quickly and quietly; older USM units can sometimes become hesitant. Check the front and rear elements for scratches, particularly the large, protruding front glass. SDS verifies the aperture diaphragm functions correctly and that the barrel shows no significant wobbling. The lens hood mount should be checked for wear, and the distance scale window should be clear and free of cracks.