RF to M Adapter?

SDFilmFan

I'm New Here
Jun 13, 2012
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Ok, I have an adapter to use my EF and EF-S lenses on my M and M50. If I bought an R I could also get an adapter to use the same lenses. The question is whether there will be an adapter to use these wonderful RF-mount lenses on M body cameras? Is it possible geometrically?

I have already decided I probably won't be buying any more EF lenses as the future looks RF and M. The eventual replacements for my 5D3 and SL1 will likely be mirrorless. But will there be a divide between the two mirrorless lines?

Mike E
 

Mt Spokane Photography

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Mar 25, 2011
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Very unlikely, the lens would have to sit inside a M or the adapter have some complex optics. EF lenses are the universal solution. The issue is due to the 18mm the rear of a RF lens sits from the sensor, while the M is designed for lenses to be 20mm from the sensor. Any adapter using lenses to make it work will likely be a kluge or very expensive.
 

tapanit

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CR Pro
Jul 17, 2012
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Ok, I have an adapter to use my EF and EF-S lenses on my M and M50. If I bought an R I could also get an adapter to use the same lenses. The question is whether there will be an adapter to use these wonderful RF-mount lenses on M body cameras? Is it possible geometrically?
I don't think it could be done without optical elements and that'd mean it'd be expensive or lose too much image quality to make sense. Also it isn't clear how easy it would be to do electronically - do RF lenses work without all the extra pins M bodies have no idea how to use? If not, the adapter would also require complex electronics, driving the price even higher. So I doubt one will ever be made.

One caveat though: a speedbooster-type adapter could make sense. It would still be expensive but the price might be more palatable if you get bigger apparent aperture as extra benefit.
 

padam

EOS R
Aug 26, 2015
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Very unlikely, the lens would have to sit inside a M or the adapter have some complex optics. EF lenses are the universal solution. The issue is due to the 18mm the rear of a RF lens sits from the sensor, while the M is designed for lenses to be 20mm from the sensor. Any adapter using lenses to make it work will likely be a kluge or very expensive.
It is exactly the opposite: 20mm for RF and 18mm for EF-M

The question has been asked in an interview before and the answer from Canon's representative was: "It can be done, but at the given size, the tolerances have to be extremely tight to do it". So I think what he meant was: it is not feasible.


One caveat though: a speedbooster-type adapter could make sense. It would still be expensive but the price might be more palatable if you get bigger apparent aperture as extra benefit.

A focal reducer already exits.
It works for FF EF lenses (or APS-C as well if one is intending to shoot cropped 4k on the M50)

Canon might make an own version (the patent suggests it would be 0.8x instead of 0.71x) that will cost more.
 

andrei1989

EOS RP
Sep 1, 2014
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Very unlikely, the lens would have to sit inside a M or the adapter have some complex optics. EF lenses are the universal solution. The issue is due to the 18mm the rear of a RF lens sits from the sensor, while the M is designed for lenses to be 20mm from the sensor. Any adapter using lenses to make it work will likely be a kluge or very expensive.
it's the other way around: R has a flange distance of 20mm and M has 18mm so in theory you could have a 2mm adapter but it's tricky to fit any electronics inside..
 

padam

EOS R
Aug 26, 2015
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I think it highly likely that if Canon are doing an EF->EF-M speedbooster they will also do an RF->EF-M speedbooster.
The latter is not possible, you can only use SLR lenses covering a wider sensor area with a speedbooster, there is a simple explanation here:

 

jolyonralph

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The latter is not possible, you can only use SLR lenses covering a wider sensor area with a speedbooster, there is a simple explanation here:
It's perfectly possible. RF lenses cover the full frame area, so with a speedbooster an RF lens could theoretically be adapted to compress the output down to an APS-C coverage of the EOS-M sensor. As it has optic elements to adjust light path you can work around the fact that the RF lens and EF-M mount have very similar flange distances although I'm sure it's not as straight forward as an EF->EF-M speedbooster it's absolutely possible.
 

Rocky

EOS R
Jul 30, 2010
982
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It's perfectly possible. RF lenses cover the full frame area, so with a speedbooster an RF lens could theoretically be adapted to compress the output down to an APS-C coverage of the EOS-M sensor. As it has optic elements to adjust light path you can work around the fact that the RF lens and EF-M mount have very similar flange distances although I'm sure it's not as straight forward as an EF->EF-M speedbooster it's absolutely possible.
All of these in 2 mm space??? Good luck to that
 

Linteria

EF-M Believer
Oct 23, 2020
7
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I think it highly likely that if Canon are doing an EF->EF-M speedbooster they will also do an RF->EF-M speedbooster.
The problem is, to my knowledge, there is no such EF-EFM speedbooster from Canon on the market or in the works. Only 3rd party. But i would love an RF-EFM adapter, even without focal reducing optics. I'm less than 4 months into my first M mount cameras. Future-proofing them would be amazing.
 
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Eagle Eye

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Jul 5, 2011
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I think a speed booster from Canon would make a lot of sense. It future proof’s your purchase of Canon products. I abandoned my 6D and EF L glass to build an M system. I’d love to add some RFs to it. When Canon eventually drops the M system, my possession of RF glass would make switch to the R system far more likely than going to another brand. I think Canon would be foolish to abandon the M system before they’ve found a way to encourage M shooters to purchase RF glass (or an EOS R body to use with EF-M glass).
 
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jolyonralph

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The problem is, to my knowledge, there is no such EF-EFM speedbooster from Canon on the market or in the works. Only 3rd party. But i would love an RF-EFM adapter, even without focal reducing optics. I'm less than 4 months into my first M mount cameras. Future-proofing them would be amazing.
Well, two years on that never happened, and Canon aren't doing an EF anything any more. I also doubt they'll do speedboosters.

You'll never get any adaptor to do RF to EF-M. It can't happen. EF->EF-M speedboosters already exist though.
 

jolyonralph

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I think a speed booster from Canon would make a lot of sense. It future proof’s your purchase of Canon products. I abandoned my 6D and EF L glass to build an M system. I’d love to add some RFs to it. When Canon eventually drops the M system, my possession of RF glass would make switch to the R system far more likely than going to another brand. I think Canon would be foolish to abandon the M system before they’ve found a way to encourage M shooters to purchase RF glass (or an EOS R body to use with EF-M glass).
The M bodies can't understand the RF protocols, which are done with a more modern faster interface than either EF or EF-M. So, no way that RF lenses will ever be adapted to EF-M bodies, sorry.