A step up ring lets you attach a larger filter to a lens with a smaller thread size, while a step down ring does the reverse, fitting a smaller filter onto a larger thread. Either way, the goal is the same: reusing one set of filters, such as an ND or polariser, across multiple lenses instead of buying a separate filter for every thread size you own.
This is especially useful if you shoot with several lenses that each take a different filter diameter, since a small, inexpensive ring can save you from duplicating your filter collection. Rings are typically labelled by their two thread sizes, so it's worth checking your lens's filter thread diameter (usually printed on the lens barrel or cap) before ordering. Available in-store and online, with our team on hand to help you find the right size if you're not sure.
