For telephoto and super-telephoto lenses such as FA star lenses. Brightness decreases by 2 stops, but the focal length of the main lens can be doubled. It matches particularly well with the FA Star 200mm F2.8 ED (IF), allowing it to be used as a 400mm F5.6 super-telephoto lens while retaining its excellent imaging performance. In that case, the minimum focusing distance remains unchanged at 1.2m, enabling high-magnification close-up photography.
