
The lens rotation ring allows for macro close-up photography with the lens when it is turned upside down. The phenomenon is familiar, for example, when looking through binoculars upside down, where a very close object is magnified as if it were viewed through a microscope (the focus distance is very narrow).
The lens rotation ring works best with fast short focal length lenses, e.g. 50mm is usually good, the wider focal length makes the subject appear even larger but at the same time the depth of field of the image narrows. The suitability of other lenses for reverse macro photography can be tested visually with the lens first.
The rotating ring works by attaching it to the filter thread of the lens. This combination is then attached to the camera body. The rotating ring has a male thread on one side and a normal bayonet mount for the lens on the other. Of course, no electrical data passes between the optics and the camera.
Then just shoot in a completely new style. Of course, this reverse shooting method is best started by shooting completely still subjects, as the subject may need to be right at the back of the lens before the image is sharp.