55mm-55mm coupling/reverse adapter

Coupling rings are adapters with a male filter thread on each side. They allow you to connect two lenses by their filter mounts. The lens that is furthest from the camera is mounted in reverse and acts as a powerful and well-corrected close-up lens. A 50 mm lens is +20 dioptres, much stronger than normal close-up lenses.

The reversed lens should be used at maximum aperture. The two lenses should be as close together as possible, so it is best to remove any filters before coupling. Long and/or heavy lenses should not be reversed, because they would place too much strain on the filter mount.