Lens mounts explained

The lens mount is where the lens locks onto the camera. It decides which lenses fit, which adapters work and which second-hand lenses you can use. You will probably replace the body within a few years, but the mount shapes what you can buy for much longer.

What a lens mount is

A mount does three jobs:

• Mechanical. It holds the lens at an exact distance from the sensor and carries its weight.
• Electrical. Contacts carry power and data, so the camera can drive autofocus, set the aperture, read the focal length for stabilisation and correct lens flaws.
• Optical. The size of the opening and its distance from the sensor set limits on lens design.

The electrical language is usually the camera maker's own. Some makers share it with other lens brands; others keep it closed.

Flange distance

Flange distance is the gap between the face of the mount and the sensor. Lenses are built for that exact gap; make it longer and they will not focus to infinity.

DSLRs need a long gap to make room for the mirror. Mirrorless cameras have none, so most of their mounts sit 16 to 20 mm from the sensor. That one number explains most of what you can and cannot adapt.

Throat diameter

The throat is the mount's inner opening. A wider one gives designers more room, especially for very fast lenses. Nikon Z is 55 mm across, Canon RF 54 mm and Sony E 46.1 mm. Width does not guarantee better lenses, though: Sony makes an f/1.2 lens, the FE 50mm F1.2 GM, for its narrower E-mount.

The mounts at a glance

Mount	Flange distance	Formats	Introduced
Nikon Z	16 mm	Full frame, APS-C	2018
Fujifilm X	17.7 mm	APS-C	2012
Sony E	18 mm	Full frame, APS-C	2010
Micro Four Thirds	19.25 mm	Four Thirds	2008
Canon RF	20 mm	Full frame, APS-C	2018
L-Mount	20 mm	Full frame, APS-C	2014
Fujifilm G	26.7 mm	Medium format	2016
Canon EF	44 mm	Full frame, APS-C	1987
Pentax K	45.46 mm	Full frame, APS-C	1975
Nikon F	46.5 mm	Full frame, APS-C	1959

Our mounts page lists what we track for each.

The current mirrorless mounts

Sony E

Sony launched E-mount in 2010 on its APS-C NEX cameras and added full-frame stills cameras with the A7 and A7R in 2013. In 2011 it began licensing the mount's specification to other lens makers without royalties.

Canon RF

Canon introduced RF in 2018 with the EOS R. APS-C bodies and RF-S lenses followed in 2022. Canon's EF-EOS R adapters let EF and EF-S lenses autofocus on RF bodies; with EF-S lenses, full-frame bodies switch to a 1.6x crop.

Nikon Z

Nikon Z arrived in 2018 with the full-frame (FX) Z6 and Z7; APS-C (DX) bodies followed from 2019, starting with the Z50. It has the shortest flange distance and widest throat of the full-frame mounts. The FTZ and FTZ II adapters take many F-mount lenses.

Fujifilm X and G

Fujifilm runs two mounts. X-mount, from 2012, is APS-C only. G-mount, from 2016, is medium format, with sensors of about 44 × 33 mm. Their lenses are not interchangeable.

L-Mount

Leica introduced the mount in 2014. In 2018 Leica, Panasonic and Sigma formed the L-Mount Alliance, so member brands share one mount. Later members include Leitz Cine, DJI, Samyang, Blackmagic Design, Sirui and Viltrox. Photo bodies come mainly from Leica, Panasonic and Sigma.

Micro Four Thirds

Olympus and Panasonic launched Micro Four Thirds in 2008. It is a shared standard, so Panasonic and OM System (the former Olympus camera business) lenses fit each other's bodies. The crop factor is 2, so telephotos are small for their reach. Combined lens-and-body stabilisation needs a supported lens and body from the same brand.

The legacy DSLR mounts

Canon EF

Canon's EF mount dates from 1987. It is fully electronic, with no mechanical focus or aperture linkage, and every autofocus lens has its own motor. EF-S lenses fit only Canon's APS-C DSLRs since the EOS 300D; EF lenses fit them all. Canon's last new EF lens design came out in 2018.

Nikon F

Nikon has used the F bayonet since 1959, adding metering, data contacts and autofocus over time, so compatibility is a patchwork:

• AI and AI-S: manual focus, with an aperture ring.
• AF and AF-D: focused by a screw motor in the body, which Nikon's entry-level DSLRs and all Z cameras lack.
• AF-S, AF-I and AF-P: motor in the lens.
• G and E: no aperture ring; E lenses set the aperture electronically.

On the FTZ or FTZ II, AF-S, AF-I and AF-P lenses autofocus. AF and AF-D lenses keep metering but focus by hand.

Pentax K

Pentax introduced K-mount in 1975, and Ricoh still sells K-mount DSLRs under the Pentax name. The bodies accept lenses going back decades, though older ones lose some automation. Many K lenses have aperture rings, so they adapt easily to mirrorless bodies.

Adapting lenses: what works and what does not

The flange-distance rule

An adapter is mostly a precise spacer, which gives one firm rule:

• Long to short works. A lens goes on a body with a shorter flange distance if the adapter fills the difference. EF lenses (44 mm) go on RF bodies (20 mm) through a 24 mm adapter.
• Short to long does not. Without glass in the adapter the lens cannot focus to infinity, and that glass acts as a weak teleconverter, costing some light and usually sharpness.

So mirrorless lenses do not go on DSLRs, and Canon's own EF-M lenses (18 mm) cannot go on RF (20 mm). Nikon Z lenses cannot go on any other mount here. Between the 16 to 20 mm mirrorless mounts the gaps are tiny, but thin electronic adapters exist for some pairs, such as Sony E lenses on Nikon Z bodies.

Autofocus and electronics

The camera makers' own adapters are built for their older lenses: Canon's EF-EOS R, Nikon's FTZ and Sony's LA-EA range for its A-mount lenses.

Cross-brand electronic adapters, such as Canon EF to Sony E, usually work by reverse engineering. Autofocus can be slower and tracking less reliable, and a camera firmware update can break compatibility until the adapter maker fixes it. Check the maker's compatibility list and whether the adapter takes firmware updates.

Manual lenses

Manual-focus lenses with an aperture ring are the easiest to adapt. A simple adapter is enough, and focus peaking and magnification help. With in-body stabilisation, you may need to enter the focal length by hand.

Lenses without an aperture ring are harder. Nikon G and older ringless Pentax lenses need an adapter with its own aperture control; Canon EF and Nikon E lenses need an electronic one.

Leica M rangefinder lenses (27.8 mm) adapt to almost any mirrorless mount with a simple adapter.

Sensor coverage

An APS-C lens on a full-frame body leaves dark corners unless the camera crops; Canon, Nikon and Sony full-frame bodies can crop automatically for their mount's APS-C lenses. A full-frame lens on a smaller sensor frames tighter: a 50 mm lens frames like about 75–80 mm on APS-C and 100 mm on Micro Four Thirds. A focal reducer, an adapter with glass, narrows that difference and makes the lens brighter, but only from a larger format to a smaller one.

Adapting is a good bridge between systems, but expect compromises if it is your whole plan.

Third-party lenses, mount by mount

• Sony E: a very wide choice. Sigma, Tamron, Samyang, Viltrox, Tokina and others make autofocus lenses.
• Nikon Z: Nikon licenses the mount to Sigma, Tamron and Cosina (Voigtländer). Other brands, such as Viltrox, sell Z-mount lenses too.
• Canon RF: Canon allows third-party manual-focus lenses, and autofocus lenses only for APS-C, which Sigma and Tamron make. Earlier full-frame autofocus lenses from Samyang and Viltrox were withdrawn, Viltrox's at Canon's request.
• Fujifilm X: open to third parties, including Sigma, Tamron, Viltrox and Tokina.
• Fujifilm G: autofocus lenses are mostly Fujinon; third-party lenses were manual focus until 2026.
• L-Mount: Leica, Panasonic and Sigma lenses are all native, plus alliance members such as Samyang, Sirui and Viltrox.
• Micro Four Thirds: Panasonic and OM System, plus Sigma and many manual-focus makers.
• Canon EF, Nikon F and Pentax K: decades of third-party lenses, much of that choice now second-hand.

Why the mount matters more than the body

The body is the part you replace. Lenses usually stay, and come with you when you upgrade within a mount.

So start with lenses. List the two or three you would buy first, plus the one you expect to want next: a long telephoto for wildlife, small primes for travel, fast primes for low light. Check they exist on that mount, new or used, at prices you can pay. Our lens listings and camera finder help.

Switching later is costly: you sell lenses at used prices and buy again. Mounts can also end. Canon EF-M, Samsung NX and Nikon 1 all stopped getting new bodies and lenses, so a mount its maker is still developing is the safer bet.

Then compare bodies on that mount; your lenses will outlast whichever you choose.

Buying across markets

Some manufacturer warranties cover only the country or region of sale, so a lens imported from elsewhere may not be covered. Your rights against the seller are separate:

• UK: the Consumer Rights Act 2015 gives you 30 days to reject a faulty item for a refund.
• EU: sellers owe at least a two-year legal guarantee (some countries allow one year for used goods), and a defect that appears within a year of delivery (two years in some countries) is presumed present at delivery.
• Australia: consumer guarantees apply alongside any warranty, cannot be taken away and have no fixed end date.
• Singapore: under the Lemon Law, a defect that appears within six months of delivery is presumed present at delivery unless the seller proves otherwise.
• US: there is no national guarantee like these. You rely on the warranty, the return policy and state-law implied warranties, which most states let sellers exclude by selling "as is".

These rights cover buying from a business; a private second-hand sale gets far less protection. Our deals page shows retailer prices in each market.