With the advent of mirrorless cameras, there was a shift in registration distance for lenses. That opened possibilities to use existing lenses on these newer mounts.
Various lens adapters. |
The official Canon EF-EOS M adapter:
B&H Photo Video, Amazon, Used on KEH, and eBay.
Metabones Speed Booster 0.71x Adapter for Canon EF to EF-M Mount:
B&H Photo Video and Amazon
Viltrox EF-EOS M2 Speed Booster 0.71x Lens Adapter:
Amazon, eBay, B&H Photo Video, and used on KEH.
As an affiliate of these shops, I earn from qualifying purchases!
This is all about flange focal distance. It’s the distance from the lens mount ring to the sensor or film plane. https://en.wikipedia.org/wiki/Flange_focal_distance
Older camera systems have a long distance. Newer camera systems have a short distance. So that means with something between an old lens and a new mount you can make the combination work.
The distance is measured in millimeters.
A few examples:
- Canon FD: 42mm
- Canon EF: 44mm
- Canon EF-M: 18mm
- Nikon F: 46.5mm
- Nikon Z: 16mm
- M42: 45.46mm
- L39: 28.8mm
The 30D next to the M50. You can see the difference inside the sensor area. |
A little test you can do is holding a lens like the EF 50mm in front of the M50 camera without a lens. Moving it back and forth shows where that registration distance is… the same as the thickness of the adapter.
![](https://photographybanzai.com/wp-content/uploads/2020/04/m50-no-adapter-ef-lens-test.jpg)
The details of adapters are not so simple.
Let’s talk about some of the adapter types…
It’s a metal tube with the proper connections. |
The cheapest and most common have no control through the camera or any levers.
- Cheapest more available type.
- The simplest option for old film era lenses because you don’t need anything more.
- If your lens doesn’t have a manual aperture then you will not be able to adjust it. This is the case for Canon EF lenses. You can see the two that I have would not work with a basic adapter.
This Nikon-F to Canon EF-M adapter has a mechanical ring for Nikon lenses that have a mechanical aperture. |
There are adapters that have a mechanical way to control aperture. This depends on the lens being adapted. Only certain ones have mechanical properties to them that allow this type to work.
- Some older lenses had a physical lever for controlling aperture. In my case I have a Nikon F-mount lens with the lever and an M42 lens with something similar.
- The adapter I have for F-mount does physically adjust the adapter, but it is imprecise with no way to set a specific value.
The official Nikon F to Z adapter has full control with some lenses, but the d-type lenses without a motor inside can’t autofocus. |
Some control through the camera.
- There are adapters that allow for some level of control.
- For example, the official Nikon F to Z mount adapter can control aperture, but does not have a motor for autofocus with D-type lenses.
- These are better than basic adapters when you need some level of control through the camera.
- There are other adapters that have quirks or limitations like not being able to do a special focusing mode that a native lens would be able to do.
Canon EF lenses have a more technological design, so nothing special is needed with the adapter to allow for full control from RF and EF-M. |
Adapters with full control through the camera.
- These adapters allow for the same amount of lens control compared to a native lens usually.
- The official Canon EF lens adapters for EF-M and the RF mount have full control.
The Viltrox speedbooster next to the official Can EF EOS M adapter. |
Speedbooster adapters (focal reducer)
- https://en.wikipedia.org/wiki/Telecompressor
- These adapters take lenses meant for a larger format such as Full-Frame but focus the light into the area of a smaller format like APS-C.
- It reduces focal length and increases lens speed.
- You can see that my Viltrox 0.71x speedbooster is physically shorter than the standard adapter and it has optical glass inside.
- Most of these adapters are fully electronic and work with a specific lens and mount combination.
- These tend to be some of the most expensive types of adapters.
- Expect overall image quality to depend on the optics of the speedbooster.
Other more obscure adapters
- The company Fotodiox has a large number of specialty adapters from tilt/shift to internal iris and auto focusing.
- Canon’s official EF to RF adapter with a built-in variable ND filter or circular polarizer. Their adapters also allow for a custom control ring.
I hope that helped you understand what lens adapters for mirrorless lens adapters do. Having a change in flange focal distance allowed for a lot of inventive adapters to be created. It’s a reason to hold on to your older lenses and a reason to pick up a mirrorless camera if you haven’t yet.