Lens Mounts Explained: What Fits What

A lens mount is the physical and electrical standard where a lens meets a camera — the metal ring, the locking pins and the row of electronic contacts. Lenses only fit their own mount. Because bodies get replaced every few years and lenses can outlast three of them, choosing a mount is the longest-lasting decision you make in photography.

The mount does three jobs at once. Mechanically it holds the lens at a precise, fixed distance from the sensor — that distance is called the flange focal distance and it is why you cannot simply machine an adapter between any two systems. Electronically it carries autofocus, aperture and stabilization data between lens and body. And commercially it defines which catalog of lenses you are allowed to shop in, which is the part that costs you money for the next decade.

The mounts you will actually encounter

Two things in that table surprise people. First, Micro Four Thirds is the only mount shared between manufacturers — a Panasonic lens fits an OM System body and vice versa. Every other mount here belongs to one brand. Second, Sony, Canon and Nikon each use a single physical mount for both their crop-sensor and full-frame cameras, which is convenient and also the source of most of the confusion below.

Crop and full-frame lenses on a shared mount

When one mount serves two sensor sizes, lenses come in two flavors: those that project an image circle big enough to cover a full-frame sensor, and smaller, cheaper, lighter ones that only cover a crop sensor. Manufacturers label the crop versions — Canon calls them RF-S, Nikon calls them DX, Sony marks them E rather than FE.

The rules that follow are simple and worth memorizing. A full-frame lens works perfectly on a crop-sensor body. The camera uses the middle of the image circle; the only costs are that the lens is bigger and pricier than it needs to be, and the field of view is narrowed by the crop factor. A crop lens on a full-frame body works, but the camera crops to avoid dark corners, so you lose a large share of your resolution. In practice: buy crop lenses if you have a crop body and want small and cheap; buy full-frame lenses if you might move up. Our crop factor guide covers what the narrowing actually does to your framing.

Adapters: when they work and when they do not

The good case — a brand's own DSLR adapter

Every major maker sells an adapter to put its own older DSLR lenses on its new mirrorless bodies: Canon EF lenses on RF bodies, Nikon F lenses on Z bodies via the FTZ, Sony A-mount on E. These work properly, keeping autofocus and aperture control on modern lenses, because mirrorless mounts have a shorter flange distance than DSLR mounts, so the adapter simply fills the gap with the right amount of space and passes the signals through. This is a genuinely excellent route to cheap glass — decades of second-hand DSLR lenses become available to you. The costs are length, a little weight, and the adapter itself. See mirrorless vs DSLR for more.

The mixed case — third-party cross-brand adapters

Adapters that put one maker's lenses on another maker's bodies exist and vary enormously. Some are excellent for manual-focus use. Autofocus performance across brands is usually degraded, sometimes badly, and firmware updates on either side can break compatibility overnight. Treat these as a specialist tool for a lens you specifically want, not as a general strategy for saving money.

The impossible case

You cannot adapt a lens onto a body whose mount has a longer flange distance than the lens was designed for without adding optical elements — and those elements degrade the image and change the focal length. That is why you can put DSLR lenses on mirrorless bodies easily and cannot go the other way. If someone offers you an adapter that sounds too convenient, this is usually why it is not.

How to use this when you are shopping

Before you buy a camera, spend twenty minutes looking at the lens catalog for its mount at the prices you can actually afford — not the flagship glass, the ones you would buy. That list is what you are really purchasing. A body with modest specs and a rich, cheap lens catalog will serve you better over five years than a specification-leading body with three expensive lens options. Our Sony vs Canon vs Nikon comparison has that lens-range comparison in table form.

And when you buy a lens second-hand, check the mount before anything else. It is the single most common way people waste money on a bargain — the lens arrives, and it does not fit. Our used camera guide covers the rest of that checklist.