If you mount existing lenses the other way round, you will get excellent close-up lenses. Photography shops have suitable adapters, or you can make the holder yourself with two adjustment rings. They bring together filters and lenses of varying diameters.
Stick the rings together with a strong quick adhesive. Then screw for example one telephoto lens and the normal lens together. An example from practice-use
a 100 mm telephoto lens and a 50 mm normal lens in an inverted position. This way, by simple calculation, you will get a 100:50 times magnification.
To get a higher depth of field, you should turn the aperture numbers in the case of the telephoto lens to 16. With this setting, rays of light go through the middle of the tube. In the case of an additional lens, set the highest exposure-in many lenses, the aperture is 2.8. Since the brightness of both lenses will be added, you must take into account long exposure times and so a tripod is an absolute must for sharp images.