A reversing ring is a very cheap way to turn an ordinary lens into a macro lens.

They work by allowing you to mount a lens the wrong way round. A bayonet fitting goes onto the camera body, then you screw the filter end of a lens onto the reversing ring.

Most lenses will focus much closer when mounted the wrong way round.

This one is a 52mm ring, enabling me to mount my Nikkor 50/1.8. This provides focus at around 10cm from the lens.

The quality obviously doesn't match a proper macro lens, but if you just want the occasional play with macro photography, as I do, then it can be just the thing.

Here's a simple test-shot - I'll add some proper examples when I start playing with it. You can see from the test-shot just how thin the depth of field is!