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?
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.
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.
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.
The flange focal distance on the Canon EOS 90D (above) is significantly greater than on the mirrorless Canon EOS RP.
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.
Mount |
Camera type |
Sensor |
Flange focal distance |
Canon EF |
Canon DSLR |
Full frame & APS-H |
44 mm |
Canon EF-S |
Canon DSLR |
APS-C |
44 mm |
Canon EF-M |
Canon system camera |
APS-C |
18 mm |
Canon RF |
Canon system camera |
Full frame |
20 mm |
Fujifilm X |
Fujifilm system camera |
APS-C |
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 |
Sony DSLR |
Full frame & APS-C |
44,5 mm |
Sony E |
Sony system camera |
Full frame & APS-C |
18 mm |
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.
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.
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.
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.