Moving to Mirrorless on Canon: The EF- EOS R Adapter Explained

With the recent announcement of the new Canon EOS R5 and R6 there has never been more interest in mirrorless technology amongst Canon users. Whilst the initial release of both the R, RP and the range of dedicated RF lenses showed that Canon were committed to mirrorless, its only now that serious wildlife photographers have a viable option in this range.

The incredible new autofocus found in both the R5 and the R6 is just one of the many reasons that have seen people seriously contemplating the move to mirrorless. There are a number of questions associated with the move though and one of the most frequently asked questions and stumbling blocks for existing Canon shooters is around whether their existing lenses are compatible with the EOS R range.

You'll be happy to know that the answer is YES!

The EOS R System adapters offer full compatibility with Canon EF and EF-S lenses giving Canon EOS R and Canon EOS RP owners who also own an EOS camera complete integration with their existing lenses.

eos r adapter

I'll save the Q&A for the end of the post but thought I'd share a bit more on each of the three EOS R Adapters that are available.

Mount Adapter EF-EOS R
The standard Mount Adapter EF-EOS R allows EF-S and EF lenses to be used on EOS R cameras seamlessly. Photographers who already have a collection of EF-S or EF optics can invest in the EOS R System confidently, knowing their existing lenses will work as expected.

Control Ring Mount Adapter EF-EOS R
Control Ring Mount Adapter EF-EOS R offers the same lens mount conversion as Mount Adapter EF-EOS R, but also adds a Lens Control Ring. The ring is customisable and easy to find without taking the camera from your eye offering tactile manual control over various settings. The Lens Control Ring can be programmed via the camera’s menu to adjust various settings such as aperture, shutter speed, ISO sensitivity and exposure compensation.

This is a nifty little feature but, in my first hand experience, not a must have for the wildlife photographer who is comfortable with a custom setup to control all of these variables on the camera itself.

Drop-In Filter Mount Adapter EF-EOS R
Drop-In Filter Mount Adapter EF-EOS R takes the functionality of Mount Adapter EF-EOS R and adds the ability to use drop-in filters, removing the need to fit filters on the front of a lens, especially useful for wide-angles with a large front lens element. It’s available with either a variable neutral density (V-ND) filter2 or circular polarising (C-PL) filter, and a clear (CL) filter is also available for shooting without filter effects.


Your Questions and my Answers on the EOS R Adapter

  • Q: Can I use my EF-s lenses?
  • A: Yes! The camera will automatically detect the EF-S lens and apply the relevant crop to the sensor to allow for full compatibility with the R system


  • Q:Does the adapter have any impact on AF accuracy and speed?
  • A: No not at all. It is literally a spacer with no glass elements like in teleconverters. It therefore has no impact on the maximum aperture of the lens you are pairing with the body and no impact on the AF capabilities of the camera whatsoever.


  • Q:Does the adapter have any impact on maximum aperture?
  • A: No, it literally adjusts the space between the back of the lens and the sensor to be equivalent to that found on a DSLR usually paired with EF lenses.


  • Q: Does the In Body Image Stabilisation (IBIS) function in addition to the existing image stabilisation of a lens?
  • A: The camera will automatically identify which lens has been paired to the body and decide which stabilising system is better for that particular lens and focal length. It may opt to solely use the lens IS or may opt to augment the lens IS using IBIS. Every lens and focal length will be different and it doesn't matter if it is an EF or RF lens. The IBIS will make a significant difference when paired with lenses that don't have an IS functionality. Essentially, the greater the focal length the more the camera will lean on IS of the lens, the shorter the focal length the greater the chances that the camera will augment that with IBIS. Official charts and figures on this dynamic should start to be published soon but it is not a simple case of adding the IBOS and lens IS together to get a combined value of the stabilisation that one would get.


I hope you've found this helpful and that the information will help you find peace of mind when considering whether you will be able to make use of your existing gear when moving to the mirrorless system.

One thing is for sure, mirrorless is the way of the future!

Andrew Beck

2 thoughts on “Moving to Mirrorless on Canon: The EF- EOS R Adapter Explained

  1. Apple Allen


    Thanks Andrew, just starting to look at these decisions (Big stable of EF L and 1 and 5 bodies)
    Appreciate the succinct and accurate info 👍🏻

    • Andrew Beck

      My pleasure and I honestly cannot find fault with the compatibility of the EF lenses and the R series of bodies. You won’t regret the switch!

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