The Vivitar HD4 MC AF 58mm High Definition 0.43x Wide Angle Converter is a lens attachment designed to expand your camera's field of view by providing a wider perspective for shots. It fits lenses with a 58mm filter thread, offering compatibility with many DSLR and mirrorless lenses. The converter has multi-coated (MC) optics that reduce lens flare and ghosting, enhancing image contrast and clarity. It supports autofocus (AF) functions, although performance may vary depending on the camera and lens combination. Additionally, it features macro capability for close-up photography, allowing it to focus on subjects at very short distances.