Coupling Ring

A definition of Coupling Ring

A ring which joins two lenses together by their filter threads, so that one is mounted on a camera while the other faces it. This setup allows higher-than-usual magnifications, the ratio of which is determined by the relationship between the two lenses. A 100mm lens mounted on the camera coupled with a reverse-mounted 50mm lens, for example, will achieve a 2:1 magnification ratio, while a 200mm lens coupled with the same 50mm lens will produce a 4:1 magnification ratio.