Everything you need to know about lens mounts

Lens mounts: perhaps not the most exciting topic, but a very important part of your gear. As the link between your camera and lenses, it is an essential element that defines much of your kit. All the more reason to immerse yourself in the topic.

What is a lens mount? | What are the different types of lens mounts? | Overview of the most popular lens mounts | What to look out for?

What is a lens mount?

A lens mount comprises the opening in the body of your DSLR or mirrorless camera where you attach your lenses. With different lens mounts you can attach different lenses to the body of your camera.

Bayonet mount

In days gone by, lenses were linked to the camera by a threaded connection. However, since the advent of technology such as autofocus and automatic light metering, a mechanical connection between the camera and lens no longer sufficed. Both featured electronic contact points that facilitated communication. The bayonet mount was developed to ensure perfect alignment of these points. This involves aligning a (frequently coloured) dot on the camera and body when mounting it yourself, then clamping it tight with a short twist. To detach it, you press the button next to the lens mount, and then unscrew the lens.


The bayonet mount ensures the lens is secured in its place, and the electronic points establish perfect contact.

As already mentioned, a bayonet mount lets the camera and lens communicate with each other. But another advantage is the speed and ease with which you can change lenses. As of course, you don't want to miss the moment just when you need to quickly switch between a telephoto and wide-angle lens. Another advantage is the exceptionally secure fit of the lens on the camera, thus eliminating minute shift. So you don't have to worry about botched photos due to a lens moving accidentally.

What are the different types of lens mounts?

Camera manufacturers all produce their own lens mounts, each with their individual dimensions, number of electronic contact points, and unique direction of rotation in which the lens is screwed and unscrewed. The main difference between the different mounts is the so-called flange focal distance (FFD): the distance between the mount on the lens and the sensor in the camera. This means you can't just attach any lens to any camera. Furthermore, there are also several lens mounts per brand, e.g., specifically designed for APS-C or full frame sensors.

For instance, if you have a Canon DSLR, you can't just use any lens produced by Canon. In fact, Canon also has lenses for its own mirrorless cameras, which feature a different mount. The major camera manufacturers, such as Nikon, Sony, Fujifilm, and Canon all produce lenses as well. These all use their own specific lens mounts.

Plus, there are specific lens manufacturers, such as Sigma, Tamron, Tokina, and Carl Zeiss, which offer lenses for different brands. In this instance, the same lens is fitted with a different mount. Making the lens compatible with multiple camera brands.

Flange focal distance

The flange focal distance on the Canon EOS 90D (above) is significantly greater than on the mirrorless Canon EOS RP.

Overview of the most popular lens mounts

We've summarised the most popular lens mounts in an overview, so you can quickly see which mount you'll encounter on which camera. We have also added the flange focal distance. With this, it's interesting to note the difference between DSLR and mirrorless cameras. Due to the lack of a mirror, the distance in a mirrorless camera is much shorter, so these cameras are often more compact in design as well.


Camera type


Flange focal distance

Canon EF

Canon DSLR

Full frame & APS-H

44 mm

Canon EF-S

Canon DSLR


44 mm

Canon EF-M

Canon system camera


18 mm

Canon RF

Canon system camera

Full frame

20 mm

Fujifilm X

Fujifilm system camera


17,7 mm

Fujifilm G

Fujifilm GFX-serie

Medium format camera

26,7 mm

Micro Four Thirds

Olympus & Panasonic system camera

Micro Four Thirds

19,25 mm

Nikon Z

Nikon system camera

Full frame & APS-C

16 mm

Nikon F

Nikon DSLR

Full frame & APS-C

46,5 mm

Pentax K

Pentax DSLR

Full frame & APS-C

45,46 mm

Pentax 645

Pentax 645Z

Medium format camera

70,87 mm

Sony A


Full frame & APS-C

44,5 mm

Sony E

Sony system camera

Full frame & APS-C

18 mm

What to look out for?

Now that you know what a lens mount is for, how it pairs the camera and lens, and the differences there are, it's helpful to highlight some practical issues.

Full frame, APS-C and the crop factor

As you can see from the overview, some mounts can be used on both full frame and APS-C cameras. Yet, lenses are often made with one of the two sensor types in mind. This is because an APS-C sensor involves a crop factor, which changes the lens' focal lengths.

So, even though the mount corresponds with your camera, a lens may still not be suitable. For example, Sony produces special lenses with an E mount for its mirrorless cameras with APS-C sensor that you can't use on a full frame camera like the Sony A7. Conversely, you can use the lenses with an E mount that are suitable for full frame (designated by Sony as FE), on an APS-C camera. Though you will have to take the crop factor of 1.5x into account. In practice, this means that the Sony FE 24-70mm is 36-105mm on, say, a Sony A6600.

Lens adapters

Mirrorless cameras are immensely popular, but making the switch from a DSLR may seem a hassle if you have a whole collection of lenses suitable for your DSLR. Fortunately, lens adapters, also known as mount adapters, provide the solution. Earlier, we mentioned the smaller flange focal distance of mirrorless cameras. Over and above the correct mechanical connections, an adapter also ensures the correct distance between the lens and sensor. This makes it theoretically possible to produce an adapter with any gradient, as long as the required flange focal distance is greater than the original mount. The same applies the other way round, but this involves making concessions in terms of lens quality and functionality.

For example, Canon has an adapter for RF to EF and Nikon one for Z to F, allowing you to use the lenses from your DSLRs on mirrorless cameras as well. Then there are independent manufacturers who produce adapters that even allow you to use lenses from an entirely different manufacturer. For instance, you can use Nikon F lenses on a Canon EF camera.

Lens mount

Think before you buy

Photographers are often very brand-loyal. This is mainly due to equipment compatibility, despite the availability of adapters. As you can imagine, someone who has been shooting with Canon for years on end isn't going to just toss aside their entire kit to spend enormous amounts of money on Sony equipment. That's why it's important to think ahead when you embark upon photography. Before you know it, you're ‘tied’ to one particular brand. Research the options a brand and the camera mount give you. This is advisable for any photographer, but especially if you think photography will grow into a major hobby or perhaps even your profession. After all, you don't want to find out after three years that you have to buy everything all over again because you would have preferred that one DSLR after all.

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