Currently I have a Canon 60D, but after carrying it with me on a trip I have started to think about a lighter camera. I want the camera to be easier to carry around for long sightseeing/tourism trips, but still be customizable with lenses. Therefore I have started to look at mirrorless cameras.

As I have a Canon camera it would be nice to be able to use my old lenses on the new mirrorless camera. Canon has an official adapter for using EF and EF-S on their mirrorless cameras, but I have read that the focusing is slower when using this adapter than the native (EF-M) lenses.

Also when looking for mirrorless cameras on the internet there seem to be other brands which offers good cameras, where you can use third party adapters for connecting Canon lenses to them. But also for these adapters, I heard there can be some focusing problems.

My questions is: will my lenses work worse on mirrorless cameras from other brands than on Canon's own mirrorless cameras? Slower focus and/or other problems? Does anybody have experience with this which they can share?

  • 2
    \$\begingroup\$ It's not much of a win to save weight on the body if the lens dwarfs it. For your purpose, you want small and light lenses, too. If you want to use the good stuff, use the dSLR. If you want to pocket it, use the folding lens with slow aperture and mediocre performance. That's the situation I'm finding. Look at the Canon EF-S 18-55 f/2.8 (650g) next to a alpha-6000 (344g with battery): what's the point of going small/light if (compared to 70D only save 400g and not pocketable? \$\endgroup\$
    – JDługosz
    May 25, 2015 at 5:33
  • \$\begingroup\$ My plan is to get a mirrorless with a small native lense. It does not need to be pocketable but I want to be able to have it around my neck for 8 or more hours when walking around in a foreign city. My current setup during my recent trip weighted 1230 gram. If I would e.g. buy Sony a6000 with E 16-50mm it would only weight 460gram. But it would be nice to be able to also use normal Canon lenses, e.g. Canon EF-S 10-18/4,5-5,6 IS STM which is much cheaper than its Sony counterpart and I would be able to use it with both cameras. It only weights 240 gram. \$\endgroup\$ May 25, 2015 at 18:46
  • \$\begingroup\$ Hey i have the same dilemma that you had... have a canon 5d dslr with a couple of lenses too. On the lookout to buy my first mirrorless camera. Just want to know if you were able to buy your mirrorless already and which one you did you get? Thanks!! \$\endgroup\$
    – user49338
    Feb 29, 2016 at 3:38
  • \$\begingroup\$ i know it's an old discussion .. but i have the same problem now ..do you find a better solution or explain at least your experience ?? \$\endgroup\$
    – Soha Name
    Oct 23, 2017 at 9:47

2 Answers 2


I don't think there's going to be a huge amount to choose from when it comes to adapting Canon dSLR lenses to mirrorless cameras. If you want autofocus and aperture control from the body, then you have to get a communicating adapter, and that's liable to be expensive, and the autofocus mechanisms being different between dSLRs and mirrorless, there's always going to be something of a performance hit across those two platforms. While using Canon lenses and a Canon adapter on an EOS M camera might get you an AF performance increase, I wouldn't expect there to be a day-and-night improvement between that, and say, a Metabones EOS to Sony E-mount adapter, given that the EOS M cameras aren't exactly lightning-fast tracking-AF performers to begin with.

Looking at the bigger picture of which mirrorless system is a good purchase candidate I think you're losing sight of the reason you want to move to mirrorless. Most of us go there to get a small, lightweight setup. And just swapping the bodies and not the lenses, too, doesn't really gain you a whole lot in terms of bulk. I think the path you're envisioning is good if you want a small lightweight second body, or you only plan on using the occasional EF/EF-S exotic lens. But if you avoid getting EF-M lenses, you're going to merely be swapping the 60D for an EOS M, but still carting all the same lenses around. And an adapter.

And if you do get EF-M lenses to go with an EOS M, the problem is going to be that there are really only two of them to choose from (18-55 and the 22), unless you live in Asia or Europe, at which point you have four to choose from. And that's still the smallest native lens lineup of all the mirrorless systems. Sony E-mount, Fuji X, and micro four-thirds have mindshare among the mirrorless enthusiasts for a reason--they're full systems. EOS M isn't one, yet, particularly for a North American customer.

Then again, I'm probably biased because I shoot both Canon dSLRS and micro four-thirds mirrorless. :D

  • \$\begingroup\$ Thanks for your answer. My plan is to get an mirror-less camera with some native lenses and use it when travelling around. I will of course still use my dSLR even if I get an adapter. The possibility to connect my old lenses to the new mirror-less camera is secondary, but it would still be nice to have the possibility. It is more important for me to have access to a larger native lens lineup. Sonys cameras look nice, but I will also take a look at micro four-thirds mirror-less. \$\endgroup\$ May 23, 2015 at 9:24
  • \$\begingroup\$ There's actually no performance hit when using EF or EF-S lenses on Canon EF-M or RF mount cameras. The EF-M protocol is exactly the same as the EF protocol, only the registration distance and shape of the mounting bayonet is different. The RF protocol is an enhanced version. The lenses perform just as well on the mirrorless cameras as they do on EF mount cameras with the same level of sensor technology and AF technology. Sure, EF-M cameras will almost certainly focus slower than Canon 1-Series cameras when using the same lens, but so do the entry level Rebel cameras that use the EF mount. \$\endgroup\$
    – Michael C
    Jun 6, 2021 at 22:58
  • \$\begingroup\$ @MichaelC, but this was written back in 2015. Why not just post a new answer saying newer tech has changed this? \$\endgroup\$
    – inkista
    Jun 6, 2021 at 23:23
  • \$\begingroup\$ Even back in 2015, there was zero translation needed when using an EF/EF-S lens on an EOS M camera. Only registration distance spacing and mount shape are needed. The signals to the lenses are pass-through. \$\endgroup\$
    – Michael C
    Jun 7, 2021 at 22:06

Canon has an official adapter for using EF and EF-S on their mirrorless cameras, but I have read that the focusing is slower when using this adapter than the native (EF-M) lenses.

Assuming the respective bodies are from the same marketing tier and have similar resolution sensors, you'll never get worse performance, either optically or in terms of AF speed/accuracy, out of an EF-S or EF lens when used with a Canon EF to EF-M adapter on an EOS M body (all of them use APS-C size sensors) than when using that same lens on a comparable Rebel or x0D body.

Again, EF-S and EF lenses will perform just as well on an EF-M or RF mount Canon body as they perform on APS-C and FF bodies, respectively, in the EF mount system when the cameras being compared have the same level of sensor technology and AF technology.

I have read that the focusing is slower when using this adapter than the native (EF-M) lenses.

Unlike when using an EF/EF-S lens on a non-Canon mirrorless camera, no EF autofocus or any other lens to camera communication has to be "translated" by the adapter when adapting any EF/EF-S lens to any EOS M or EOS R camera. The only reasons an adapter is needed at all is to account for the differing registration distances and shapes of the mounting bayonets between EF/EF-S, EF-M, and RF lenses.

Where you lose out when using EF and EF-S glass with EOS M and R Series cameras is when comparing them to the newer EF-M and RF mount lenses. The best RF mount lenses tend to be sharper and faster focusing than the best EF mount lenses with the same focal lengths and maximum apertures. They also tend to be modestly to exceedingly more expensive. As the saying goes, you usually get what you pay for.

Remember, there are more expensive and/or newer EF mount lenses that focus faster on the same EF mount bodies than cheaper and/or older EF mount lenses focus on those same EF mount bodies. Many EF/EF-S mount lenses also focus faster on higher tier and/or newer EF mount bodies than those same lenses focus when used with cheaper/older EF mount bodies, too.

The EF-M autofocus protocol is exactly the same as the latest revisions of the EF/EF-S AF protocol. If EF-M lenses focus faster on the same EOS M body than an adapted EF/EF-S lens, it's because the EF-M lens has a faster AF motor than the EF/EF-S lens, just as there are some EF/EF-S lenses that focus faster on the same EOS bodies than other EF/EF-S lenses can focus on that same EOS body.

Incidentally, due to the very small 2mm difference in the registration distances of the EF-M an RF mounts, as well as the differences in throat diameter and the shape and depth of the bayonet lugs (which exceeds 2mm), it's physically impossible to adapt an RF lens to an EF-M camera and have focus at any distance beyond macro distances without using additional optical elements that also act as a teleconverter.

The Canon RF autofocus protocol is an enhanced extension of the EF protocol that is fully backwards compatible with the EF AF protocol. EF and EF-S lenses will perform no worse on an EOS M camera or RF mount camera than they are capable of performing on an equivalent EF body. In some cases, second generation RF mount cameras like the R5 and R6 can focus the same EF/EF-S lens noticeably faster than the lower tiered EF mount Rebel series and older models of the x0D series of cameras can focus those same EF/EF-S lens. (Newer EF mount cameras, such as the EOS 90D, can sometimes AF faster with certain EF/EF-S lenses than an older or lower tier EOS M body can AF with the same lenses, though.)

Sure, EF-M cameras will almost certainly focus slower than Canon 1-Series cameras that use the EF mount when using the same lens, but entry level Rebel cameras that use the EF mount also focus the same lenses slower than their 1-Series counterparts, even though they are both EF mount camera bodies.

If you use an EF-S lens with a full frame EOS R body, the image will be automatically cropped to use only the center of the FF camera's sensor that is the same size as APS-C sensors. So that 20MP FF EOS RP becomes an 8MP APS-C camera when adapting an EF-S lens to it. The 45MP EOS R5 becomes a 17MP APS-C camera when an EF-S lens is adapted to it. This is necessary because the usable image circles of EF-S lenses are only large enough to cover that smaller APS-C sized area.

I want the camera to be easier to carry around for long sightseeing/tourism trips, but still be customizable with lenses.

With regard to smaller and lighter, though, there's not really much of a loss of total size/weight when going from the best EF lenses on EOS EF mount bodies to the best RF lenses on EOS R bodies. Much of what you lose with the body is often gained with the lens. There's also less difference in size/weight when going from the smaller, lighter lenses with narrower maximum apertures in the EF-S system to the lenses in the EF-M system than there is when going from larger and heavier higher performing EF lenses to smaller and lighter EF-M lenses with narrower maximum apertures. There's even less difference when using the same EF/EF-S lenses with an EOS M body plus adapter than when using the same EF/EF-S lenses with one of the smaller and lighter EF mount bodies.

This is also the case with most other manufacturers of mirrorless systems. Have you seen the size of some of the Sony GM E-mount lenses? Or the Sigma ART lenses for mirrorless mounts? They're about as small and light as a full mayonnaise jar. Sure, most EOS M bodies are smaller and lighter than most EF bodies. The EF mount Rebel SL series might be slightly smaller than the largest EOS M cameras, though. The Rebel SL series is certainly smaller than the larger models in the EOS R series.

In the specific case of your 60D, the only EOS M camera that has comparable performance in terms of things such as Servo AF, frames per second, etc. is the EOS M6 Mark II, which also happens to be one of the larger/heavier EOS M bodies, especially if one adds the optional EVF to the M6 Mark II hot shoe. (Of course tying up the hot shoe as the only way to have an eye level viewfinder, coupled with the lack of a PC port¹ is the M6 Mark II's Achilles heel, in my opinion, as it means one can not use an eye level viewfinder and control external flash at the same time!)

To get an RF lens that performs as well as, say the EF 24-70mm f/2.8 L II, one must use the RF 24-70mm f/2.8 L IS, which is just as large and heavy as the comparable EF lens.

¹ PC in the context of flash photography has nothing to do with a personal computer. It is an abbreviation of Prontor/Compur. Prontor has its origins in the Italian word pronto (quick) and was a brand of shutter produced by Alfred Gauthier in the 1950s. Compur, derived from the word compound, was the shutter brand of the Deckel Company. Both companies were based in Germany and both counted Zeiss as an influential stockholder when they introduced the standard 1/8"-inch coaxial connector for shutter/flash synchronization.


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