What the standard defines
A diameter in millimetres and a thread cut to a fine pitch, printed on the front of a lens beside a ⌀ symbol. Any filter of the same figure screws in. There is no organisation publishing a list of permitted diameters, and no document to appeal to when two figures differ by a millimetre — there is only what each maker cut and printed.
The practical effect is that the number is reliable where it appears. A lens marked 58 takes 58 mm filters, from any maker, in any order, stacked or single. That is a narrow promise kept exactly.
What it does not promise
Nothing about the camera. The thread is on the lens. Two lenses for the same body routinely differ, and a filter bought for one may not fit the other — the four titles here that print a diameter print three different ones.
Nothing about the filter’s depth. Diameter is settled; thickness is not. A thick mount on a wide-angle lens can appear in the corners of the frame, and this is why some filters are sold as slim. Where a maker publishes a mount thickness, it is publishing something the diameter does not cover.
Nothing about the hood. A hood bayonets or screws onto its own fitting, and adding a filter or a step-up ring changes what will still attach in front of it. No listing in this catalogue addresses the combination.
Nothing about stacking. Two filters screwed together sit further forward than one. Whether that shows in the frame depends on the focal length, and it is not described by any figure either filter publishes.
What it works with
Every lens that carries a thread, and every filter, cap and step ring that names a diameter. Lens hoods attach to their own fitting rather than to this thread, and close-up lenses screw into it exactly as a filter does — which is why they sit in this group rather than among the optics.
What people ask before they commit
Do all lenses for one camera take the same filter size?
No, and this is the most common wrong assumption on the shelf. The thread belongs to the front of the lens, so two lenses that mount on the same body can take different sizes — the three diameters printed in this catalogue all belong to lenses for the same handful of systems. The figure to look for is on the lens listing, usually beside the ⌀ symbol, and not on the body.
Is a step-up ring a loss of quality?
It is a change of diameter, and what it costs depends on what it puts in front of the glass. A larger filter on a step-up ring sits further forward, which matters for a wide-angle lens where the hood no longer fits and vignetting can appear at the corners. Makers publish the ring diameters; they do not publish the vignetting, and no ring listing in this catalogue mentions it.
Last reviewed 12 September 2026