Can you use Canon EF lenses on RF cameras?

The short version: yes. Fit Canon’s Mount Adapter EF-EOS R between an EF lens and any EOS R body and the lens works as it did on a DSLR, with full autofocus, image stabilisation and aperture control. The adapter has no glass in it, so image quality is unchanged.

We shoot adapted EF glass every week, including a 70-200mm f/2.8L IS II and a 135mm f/2L on an EOS R5 Mark II, and in normal use you forget the adapter is there.

Why you need an adapter at all

RF cameras sit the lens much closer to the sensor than EF DSLRs did. The gap, called the flange distance, is 20mm on RF and 44mm on EF. The adapter is a precisely made 24mm spacer that puts an EF lens back at the distance it was designed for and passes the electronic signals straight through.

Because it’s just a spacer, there’s nothing optical to degrade the picture. Sharpness, contrast and bokeh are exactly what the lens delivers on its own.

Which adapter to buy

Canon makes three versions. All of them do the basic job equally well.

• Mount Adapter EF-EOS R. The plain one. Cheapest and smallest. Fine for most people.
• Control Ring Mount Adapter EF-EOS R. Adds a clicky ring you can set to aperture, ISO or exposure compensation, like the ring on RF lenses. Handy if you shoot manual and want a spare dial.
• Drop-In Filter Mount Adapter EF-EOS R. Takes a slide-in circular polariser or variable ND filter. One filter then works with every EF lens you own, including wide lenses with no front filter thread. Popular with video shooters.

Third-party adapters are cheaper, but Canon’s own versions are the safe choice for reliable autofocus and are weather-sealed.

What works

• Autofocus: works fully, including eye and subject detection on newer bodies. Many older EF lenses focus faster on a mirrorless body than they ever did on a DSLR.
• Lens stabilisation: works as normal.
• In-body stabilisation: on bodies that have it, such as the R5 Mark II and R6, it also steadies lenses with no IS of their own. A non-IS lens like the 135mm f/2L becomes much easier to handhold.
• EF-S lenses: these work too. On a full-frame body the camera switches to a 1.6x crop automatically, so you lose resolution.

What to watch out for

• EF-M lenses won’t fit. They were made for Canon’s small mirrorless system, and there’s no adapter for RF.
• Older third-party lenses can be hit and miss. Recent Sigma and Tamron EF lenses generally work well, but very old ones can focus slowly or show errors. Check the maker’s site for firmware updates.
• Size. The adapter adds about 24mm of length, so an adapted lens is longer than an RF equivalent.

Should you switch to RF lenses?

Not in a hurry. If your EF lenses are sharp and focus well, adapting them costs very little and loses nothing in image quality. Move to RF when a specific lens gives you something your EF version can’t, such as lighter weight, faster autofocus for sport, or a focal length that doesn’t exist in EF.