Opinion: Canon is causing its own problems with the RF mount


Aug 1, 2017
So in stupid mirrorslapper world full frame lenses can mount on aps-c bodies without any adaptor but in our future mirror-free utopia full frame lenses can't be mounted on aps-c bodies even with an adaptor because the mechanical clearances are too small to allow an adaptor to fit between the lens and body. Totally clear and logical.


Jul 31, 2014
We should also consider that Canon may believe the 'problems' are minor and/or irrelevant.

Anecdotally, the use of EF lenses on APS-C bodies prior to a FF upgrade certainly occurs. There are examples on this forum, myself included. But is that typical/common? I know I'm far from typical – I had the 70-200/2.8L IS II, the 85/1.2L II, the 100-400L, and the 24-105/4L IS with the 7D, prior to getting the 5DII.

I wonder how many Canon APS-C owners upgrade to FF, how many have EF lenses when they do, and how many of those were lower IQ lenses that were replaced L lenses after the upgrade. But...whereas I can only wonder, Canon has the data. In light of those data, there maybe no real problem from their perspective.
Canon has the data on what lenses and bodies they have sold, but the only data they have on who has bought them comes from the subset of people who return the warranty registration card, who may or may not be a representative sample.
I think it's also important to consider that Canon isn't discontinuing EF, so anyone who wants to buy an L-series lens to mount to their M body can still do so in the comfort of knowing that lens will mount on an RF body in the future if they upgrade to FF. No, you won't be able to mount an RF lens to an M body, but that is a very small proportion of the lens catalogue that is affected, for much of which there are decent EF alternatives.
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Jan 5, 2013
I don't get why Canon should ditch its EF-M mount/line of lenses. The initial FR-lenses are the opposit of EF-M lenses. Chunky and expensive (L!) vs. cheap and plasticy. M is cheap, small, light and even if there is only one M lens released each year that's enough IMO. i also don't think that EF lenses are an endangered species as long as people buy them. EF-S the same: Canon has developed a lot of lenses and can sell them until no one wants them anymore, but given their much lower price than (crop adjusted) EF lenses and the cheaper crop bodys they will sell for some time to come.

But: i'm not so sure how successfull R lenses will be. The beauty of adapting EF lenses is that it's electronics only, compared to Nikons numerous F-flavors with mechanics and all that. I've been shooting Canon crop bodys for 12 years now and never considered FF because most of the time i focus to something off center and a 6D has a narrow AF point spread and a 5D is too expensive for this amateur. But this R sounds very interesting to me because slow fps but a large AF area is just what i need. But i would not consider buying a R lense like the 24-105 if i can get the more flexible EF version for a similar price or even lower when bought used.

So far the 28-70/2 seems to be the only real not-possible-in-EF lens and this beast will be way to expensive for me.

Interessting times. Can't wait for the official anouncement on wednesday about all R features and prices.
Very valid point about potential discontinuance of any of the current existing lenses. As long as their is sufficient demand, Canon will keep making them. It's called the rule of supply and demand. Glad you made this point.
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Nov 10, 2016
It is all speculation on our part that there won't be the possibility of mounting and RF lens on an M body. However, I have little interest in mounting big glass on my M50. I prefer to keep the small form factor small.
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Technically they probably can, with an EdMika-like conversion. Certainly not a commercially viable solution.

I'm really puzzled by Canon's disregard of the EOS M to EOS R upgrade path via pre-buying lenses.

Still, perhaps this is an indication that Canon doesn't intend a full RF lens lineup, and will keep the RF line limited in scope and eventually release EF FF MILCs.
If Canon releases EF FF MILC, it will be last nail in the coffin of the EF-R and would be simply hilarious. I know it sounds logical, but imagine the situation - two FF bodies, one as a backup. Would you buy any expensive EF-R lens, if it can't be used on the FF EF body too? I would not and would buy it in reverse - EF lens, which can be adapted to EF-R.
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Jul 20, 2010
Springfield, IL
Typical forum discussion. People getting their panties all in a twist before the cameras/lenses are even released.

I really don't see the problem. EF lenses remain the foundation of Canon's lens system. That's going to be the case for at least the next decade and probably longer. Canon makes three specialized mounts, one for crop DLSRs, one for crop mirrorless and, now, one for full-frame mirrorless. Those lenses are matched to the formats. I imagine that Canon's market research shows that this won't be a problem for most users.
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Pentax K-1000
Jan 20, 2014
Thetford, VT
In one of the other multitude of RF threads I raised exactly the same issue about "where does this leave the 7D?"

I think we all know the answer is that there won't be an APS-C sensor RF body, and those wanting to use lenses on both an M series and an R series camera are stuck with EF lenses and adaptors on both bodies.

Pure speculation: perhaps the new 7D could be the pro mirrorless 5 series we all assume is coming, but with a crop mode that boosts frame rate to 12.


I'm New Here
Oct 3, 2013
While EF lenses can be directly mounted on Canon APS-C cameras, somehow Canon decided otherwises for RF lenses to EOS-M bodies. This is where the problem lies, people cannot carry an R body, and M body as a backup, with a set of RF lenses only
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Antono Refa

Mar 26, 2014
Not mounting EF-M on RF is borderline whining. EF-S can't be mounted on EF either, and mounting crop lenses on EF (3rd party on Canon, DX on FX on Nikon) never impressed me as popular either. When I upgraded from 450D to 5Dmk2, I upgraded the EF-S 10-22mm to EF 17-40mm, and the sky didn't fall.

People do use long lenses on 7D, so the RF to EOS-M compatibility is a good point.


Mar 25, 2014
It is same as existing EF-S lens compatibility with EF. Not possible to mount EF-S lens on FF. But FF EF lens can be mounted on crop body. Is there any adapter to mount EF-R lens to EF-M body.


Jun 18, 2011
It is same as existing EF-S lens compatibility with EF. Not possible to mount EF-S lens on FF. But FF EF lens can be mounted on crop body. Is there any adapter to mount EF-R lens to EF-M body.
That's much less of an issue, I mean you can mount APSC lenses on FF Nikon DSLR's but theres not really a massive market for it due to the limited coverage. On the other hand you have people who shoot APSC that own FF lenses either due to their not being an APSC option(or it being no real advantage) and to potentially allow for an upgrade.

What I would say is that I think this is less of an issue on mirrorless simply because fewer people tend to shoot with tele lenses there than on DSPR which is the most likely area APSC users will own FF lenses. Indeed I suspect that Canon and Nikon will largely look to depend on adapted DSLR lenses for their tele use on mirrorless in the near future.

One thing I think this does highlight is that a small mirrroless mount for FF must be a significant disadvantage, its one thing for Nikon to introduce a larger mount without it introducing compatibility issues, its quite another for Canon to do so with the EF-M system already there. My guess is that long term we'll see its not just a case of ultra fast lenses but rather general lens performance, especially if we ever see Sigma style 3 layer sensors introduced that will likely be very unforgiving of light hitting the sensor at extreme angles.


Jul 11, 2018
In a few years EF-M and EF-S will be on lifesupport. As big as canon are, they still need to focus on that one mount. EF will have a drawn out death depending on how quickly people migrate to RF, I'd say it will take about a decade and then canon will tell us that there will be no more development of EF mount products. Any lenses released in that timeframe will be designed with the RF adapter in mind though.
Unless sensor manufacturing costs go down, I would expect the future to hold a couple of APS-C bodies. Also, it seems to me that the 7D line has been popular enough that a mirrorless equivalent could be justified.


Aug 15, 2017
Let's face it: APS-C was invented in a time that full frame sensors were very expensive. Now that that problem has been solved, who needs APS-C?
APS-C still plays a role for those who have use for smaller size and lower cost alternatives that can still provide good IQ.

When my aspirations outgrew the 1000D, I purchased a 70D. When I wanted more control over the focus point and flicker-free shots while shooting sports, I sold my 70D and picked up a used 7D Mk II. I also found a used EF-S 18-135 (Nano USM) that is a wonderful all-around lens that has no meaningful FF equivalent. If I need something brighter for close shots, I have the EF-S 17-55 f/2.8. For portrait work I got a used EF 85 f/1.8. For longer shots I got a used EF 200 f/2.8 L II (longest black L prime, 320mm equivalent on APS-C) which works very well for concerts and events, but which does not draw attention like a big white. My latest addition was a new EF-S 10-18, which cost much less than what I would have had to pay for an equivalent EF 16-35.

Before my next safari trip I plan to add the EF 100-400mm F4.5-5.6L IS II and a 1.4 III extender, which when combined on my 7D Mk II will give me a reach out to very nearly 900mm.

While adding a FF or EOS R at some point in the future is certainly within my plans, I will keep an APS-C body and many of my EF-S lenses, as they will still be useful.


Aug 26, 2015
Super 35mm (with EF mount) is also the industry standard for video production. So no, EF-S won't disappear at all (if anything, it actually kind of revived a bit with the DPAF technology).
And EF-M will continue, albeit with limited appeal, as they won't bother making a FF camera and lenses with that mount. And for now, they are probably not considering crop sensor RF cameras either. They may adapt to the market if they find that necessary, they can do many things, like a mirrorless 200D successor if they want to.
But what they are certainly not doing is hosting an emergency meeting, because this article emerged. They have widened their product range even more in recent years (even making cheap cameras with ancient Digic 4 processors) and it works for them. End of story.
Oct 12, 2013
Canon fails to offer us the mirroless benifits i.e. Light weight lenses,IBIS etc.etc. Now I am confused why Canon is creating an another mount (RF) when they are not offering any special over light weight dslrs like my 6D mkIi !!
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Oct 15, 2011
While EF lenses can be directly mounted on Canon APS-C cameras, somehow Canon decided otherwises for RF lenses to EOS-M bodies. This is where the problem lies, people cannot carry an R body, and M body as a backup, with a set of RF lenses only
Or put another way, EF lenses can mount to 4 body types. RF lenses can mount to one and only one.

I started out on APS-C. I got my first L Lens before eventually going full-frame. And at times now, yes, I slap my huge 24-70 L on my compact M3. Not always, but sometimes. And I like having the option to do it. Sometimes, there's things the 24-70 can capture that the 22mm just can't. I imagine that there are many who dip their toe into photography via APS-C before deciding that they want to jump into the deep end. I'm awaiting the official announcement like everyone else, but I'm not sold on the RF system or logic of slapping a '?' on EF's long-term future (and yes, resale value).


Apr 23, 2018
I read the observations raised in the Canon news article about starting off in an M world and not being able to migrate to FF whilst continuing to use ones existing lenses. However I am not sure how large a sector this is of the customer base. For example users who want to stay small could just stick with the M lineup in view of the impressive performance of modern APSC sensors. Users like me ( I have the EOS M and EFM 22) who want a body which is easy to drop in a pocket will have one M body and limited lenses as an add on to their kit. For users who want to migrate to a FF system then the invested value in a few EFM lenses is not great anyway compared to the cost of purchasing a FF body and FF EF or RF lenses.
exactly! agree 100%

However is there any technical reason why there could not be an APSC sensor RF body which could be used with RF lenses or EF lenses plus adaptor?
no technical reason whatsoever. Any size sensor smaller than and up to 36x24mm could be served by RF mount. Downside would be crop camera bodies and crop lenses that are not as compact as they could be with a smaller mount [like EF-M].

Throughout the DSLR era Canon has used to mount variants to optimize FF and APS-C systems in terms of optical performance and size/weight/price. With RF mount it is clear they have decided to continue this 2-mount approach also for the mirrorfree future. There is no danger at all for EF-M. But the lineup will remain as limited as EF-S is/was. No problem. Small, light, cheap = EF-M. Big, heavy, expensive = RF.

Sony decided to go 1 mount only and use APS-C E mount also for FF sensor. They and their customers have to live with the consequences of that decision. Amongst other unwanted effects like more complex, heavy and expensive lens deigns I do not think we'll ever see lenses like a Sony FE 85/1.2 or a 28-70/2.0. And even less so a 58/0.95 [although I personally doubt the necessity of such a lens].

In line with their DSLR history [1 mount, F-mount with FX and DX lenses] Nikon seems set to also go with 1 mount ("Z") for mirrorfree as well, but opposed to Sony they would use the large FF-optimized Z-mount also for APS-C cameras. Downside to that approach is that APS-C camera bodies are not possible in a very compact format, due to the physically large mount opening.
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Apr 23, 2018
Is there any adapter to mount EF-R lens to EF-M body.
No. It is way too early. But unlike the drama queen article author I don't see why such a 2mm adapter should not be technically possible. Whether Canon or will (ever) bring one out or not remains to be seen. I definitely expect it from third parties - eventually.