The EOS-M Quandary

What should Canon do with the EF-M mount?

This has been talked about even by us for a quite a while now, and a recent topic in dpreview got me thinking that there’s more to this than meets the eye.

A bit of disclosure here, I’m a long term user of the EOS-M system. I started to use it in 2013 and never really looked back with it.  I like the small form factor and the excellent image quality that you can get from both the lenses and the cameras.  I went to this system after desiring something smaller from my 7D/5D setup in the past.  Also, I started traveling more, and with carry on luggage restrictions being stricter, having a small travel camera kit became even more important.

I also will move to the EOS-RF system, most likely an EOS R, or even better, a fabled EOS Rs high-resolution camera if Canon releases one this year.

I am speaking for myself, but I don’t see what the fuss is about in terms of the EF-M mount.  This is not to say that I don’t think Canon has a problem of their own devising when it comes to the 7D system, but that’s not where the EOS-M system is.

The EOS-M system is a small travel conscious system that relies on small slow lenses and APS-C sensor size.

If you didn't know, Canon makes three different mounts right now for cameras; the EF mount which has been around since the 1980's, the EF-M or EOS-M which has been around since 2012 which works with Canon's small mirrorless cameras that use an APS-C sensor size, and the new EOS-RF full frame mirrorless system that uses the RF mount, which is physically larger than the EOS-M mount.  There is adapters that can be used for EOS-M to EF, and EOS-RF to EF, but it is physically impossible to make an adapter that allows an EOS-M camera to use an EOS-RF lens, or an EOS-RF camera to use an EOS-M lens.  Thus the problem.

There are a few scenarios that people seem to be wishing for or using the lack of ability as a problem for Canon.

Can’t mount RF lenses on the EOS-M cameras

This common scenario mentioned is that if the EOS-M system was chosen as the mount going forward and EOS-RF lenses were designed for the EOS-M mount and not for a larger RF mount.  People would use RF (full frame) sized lenses on an EOS-M mount.  I personally can’t see anyone desiring to mount an EOS-RF-sized lens with a current EOS M camera, the M5 or M50 and here’s why.  Let's assume that by changing the mount you are not dramatically changing the lens size.  As Canon has pointed out you may need to reorganize your optical design, but it should be similar enough for this discussion.

While the RF 35mm is almost a good size, it still cramps up too much where the grip is, and where your fingers and first knuckle would rub against the lens while attempting to grip onto the camera body.  Not a good solution and this is the smallest lens. If we look at the current RF kit lens, the Canon RF 24-105L, the spacing is even tighter, and the increased bulk and weight of the lens unbalances the much smaller M5.  While the EOS RP weighs almost the same as the EOS M5 (440 to 400 grams respectively), the grip is much more pronounced on the EOS RP and also the space in between the grip and the lens body is much larger as we see below.

This isn’t to say that Canon couldn’t make larger EOS-M camera bodies, of course, they can, but then the bodies are larger and thus the system starts to lose its small compact size advantage in a quick hurry.  Also, the RF lenses would have limited backward compatibility only being able to be used on EOS-M camera bodies designed to be able to ergonomically mount an RF lens.

Of course, Canon could put the EOS-M mount into the EOS R and EOS RP and thus re-use the mount, but there are other problems with that.

Canon would need to make lenses more like the physical shape of Sony FE lenses where the lens diameter narrows down to the mount diameter thus freeing up a small amount of space to squish your fingers into.  Many people have complained about this distance as being too tight between the lens and grip with Sony lenses and the mount, so I can’t see it being a benefit to repeat the same mistake.  Because of this gap controlled really by the lens, there is a hard limit to how much you can increase the size and width of the camera grip because of the lens size to the mount size.  Also because of the smaller throat and smaller EOS-M mount, larger optical elements can’t be used closer to the sensor, making the optical design less desirable than the current RF mount and full frame lenses. 

There’s also another important reason; the RF lenses right now use a much faster protocol and that’s currently used for more AF operations per second, and also because of the lens stores more digital data such as the DLO data that gets downloaded to the camera.  While EF and RF lenses will both work on an RF camera body because the protocol will switch between EF and RF, the same can’t be said for an EOS-M camera that communicates using the EF protocol.  Even if you could physically mount an RF lens onto an EOS-M camera, it simply wouldn’t even work.  So in this scenario, Canon would not be able to use the much faster and future proof RF protocol, unless they added complexity into each and every lens which would be to communicate in either EF or RF protocol depending on the camera body.  This would add both firmware development time and cost to each and every lens you purchase.

So, do I stay awake at night loathing the fact that Canon didn’t allow me to use full frame lenses on the M5? Not really.  They wouldn’t be ergonomically desirable on an M5, there would be compromises in terms of how the lenses must be fitted around the tighter grips of the smaller EOS-M cameras, electronically they would have to use the slower EF mount protocol or add expense to each lens, and while the EF-M lenses are well balanced on an M5 with a small grip, the same couldn’t be said when you start attaching bigger and heavier lenses to it.  There's a lot of good reasons why Canon choose to use a different mount.

My advice, if you have the EOS-M system, enjoy it for what it is.

You can’t migrate upwards from EOS-M to EOS-RF cameras or You can’t mount EOS-M lenses on the EOS-RF system.

The lack of migration upwards through the evolution of camera systems from the small M50 up to the larger EOS R for the new mounts from Canon is indeed a problem.  However how much of a problem is it really? If you take an EOS-M lens which is APS-C sized and could mount it on an EOS R, then you are working with a 12MP resulting image from your full frame camera body.  If you mounted it on an EOS RP, you’d get around 10MP.  The lenses also use the slower EF protocol and won’t automatically share DLO data for in-camera conversion.  Of course, this same downside really exists if you came from the EOS-M or if you used EF-S lenses in the past.  Meanwhile, on your smaller M50 camera, you get 24MP.  If you’re going to full frame, you’re also going to upgrade at least your core lenses, because if you don’t, there is no reason at all to upgrade. 

Most like you do as I will, you will keep your EOS M system as a grab and go travel kit for when I don’t want to carry around the heavier and bigger EOS RF system.  Considering that with the EOS-RF system you can augment your lenses with cheap alternative lenses from the EF system, the tangible desire to re-use APS-C lenses becomes even mooter. 

About the only benefit is because of the current crop when shooting 4K video on the EOS RP or the EOS R.  But that’s a temporary problem and not something that will occur over the long term as faster sensors and processors are developed by Canon. 

I personally don’t see a common migration happening between EOS-M and EOS-RF system where you’d want to share APS-C lenses on a full frame camera body.  You have the entire EF collection of full frame lenses to pull from for the RF mount that works seamlessly with the new mirrorless RF cameras.  While they are not as small as the EF-M lenses, they also will give you an image size of 30MP (or 26MP on the RP) instead of 12 or 10MP.  The EOS-M and EOS-RF systems just naturally seem to function the best side by side, and not intermixed together.

The solution everyone seems to want or How to get around the 7D problem

Now Canon does have an answer for all this, but it’s a painful one for Canon and one I’m sure they have considered.

The one option that Canon could do is simply re-create the EOS-M system with the RF mount.  That would essentially be a one-step solution to the problem in which Canon would very quickly;

1. Migrate the EOS-M50 to the RF mount with the current level of technology for sensor,etc.  Essentially would be a crop EOS RP.
2. Retrofit the mechanical mount differences to the existing EOS-M lenses and re-release them at EOS-RF lenses.  This would give the system a 22/2.0, 32/1.4, 18-150,11-22,15-45,50-200 kit and APS-C lens collection right from the opening bell.

Then basically Canon would let the EOS-M system die a slow death with minimal work and effort and hopefully convince people to move to the EOS-RF APS-C system. Perhaps offering trade-in discounts and other incentives to assist with the migration.

This seems to be the solution that most people favor.  It would certainly get around the problem of what to do with the 7D as you could then make a 7D mirrorless for the APS-C sensor sized RF mount system and the 7D mirrorless could use smaller APS-C RF lenses and full frame EOS-RF lenses as they come out.

But the problem for Canon with this is that the EOS-M and most specifically the M50 is a highly successful camera body.  Killing off the system would potentially significantly damage their reputation at a time that the camera market is cratering.   Not exactly a great time to pull the rug out from underneath your user base.  They could always run the two APS-C mirrorless systems side by side, but that would even greatly confuse people, having comparable systems with no interoperability.  At least with EF DSLR cameras, there is one-way interoperability.

In other words, while this would be the solution, it's just a mess for Canon to attempt to do it on a system that is only 7 years old (EOS-M).

What will Canon do?

It’s anyone’s guess. I think they just prefer to run the systems side by side and ignore the fact that the 7D camera gets caught in the middle.  Ignore the problem and hope that over time it slowly fades away.  It may just do that too. I think the sharing of lenses upward from APS-C to full frame is an overblown problem.  While I’m sure some do that, it’s usually because there are no cheap alternative lenses for the person to choose from.  A person moving to the RF system has a wealth of choice by leaning on the largest mount system ever developed, the EF mount.  These lenses take full advantage of their camera, and its sensor size, whereas the EOS-M lenses do not.  Both the EOS-M and the EOS-RF system have their strengths and weaknesses but they can both peacefully coexist as your kit, as both systems serve different use cases.