Why and when you need a step-down ring
The opposite of step-up rings are step-down rings, which essentially do the reverse: they enable you to adapt filter and lens accessories with smaller thread sizes to lenses with larger thread sizes. For example, they allow you to attach a 52mm filter to a lens with a 72mm thread size.
Step-down rings are not as widely used as step-up rings because, in most cases, the smaller filter sizes result in vignetting. The exception to this rule is when using lenses and filters designed for larger-format cameras (i.e. full-frame) on smaller-format cameras (i.e. APS-C and Micro Four Thirds). In these cases, the smaller image field will often negate any vignetting or image clipping.
For further reading about the filters to which you can apply step-up or step-down rings, click on the following links:
Metal Stepping Down Rings (Step Down Rings)
Specifications:
Material: aluminum alloy
Product manual:
1. Change the caliber adapter ring, which can be installed in front of the lens to achieve the same diameter filter, hood, additional lens and other accessories for different calibers or to increase the lens aperture.
2, the adapter ring is made of aluminum alloy, black, sturdy and durable; small diameter is external thread (with lens end), large diameter is internal thread (connected with various filters of the same diameter UV, CPL, star mirror, medium gray Mirror, close-up lens, hood, etc.).
3, light and portable, easy to install, at the same time can save money, but also can improve the problem of partial vignetting;
4, the adapter ring is a small to large conversion aperture adapter ring.
"You could say stepping rings are a win-win solution that should please both your wallet and your gear-besieged shoulders and back."