With the added thickness of this converter on a full frame, is, for instance, a 50mm lens still a 50mm lens or more like a 60mm?

OK, you need some knowledge, let me help. The basic answer is that it is still a 50mm lens, or whatever the lens is it is not effected in this way. For more info, read on. To start, you have adapting confused with crop factor, and crop factor only applies to sensor size, not the distance the lens is to the sensor. And to make it even more muddy, crop factor doesn't change the focal length of the lens, it changes the field of view. I'll try to explain each thing.. Adapting - So, this adapter makes it so older EF lenses can work on the new RF system. The new cameras do not have the mirror the older cameras do, and thus allow the new lenses to be placed much closer to the sensor. This is called "flange distance". Lenses are designed to focus based on this lens distance. So the older lenses require a much longer flange distance, and the adapter creates that space, otherwise the lenses wouldn't be able to focus (or fit, they are engineered to make it so you can put them on the wrong camera). It makes no changes to the function or properties of the lens, and no crop factor applies. Crop Factor - This can get complicated, I will try to stick to the basics. Crop factor only applies if the sensor size is different, usually in this case it means the sensor is smaller, but some sensors can use a "crop mode" which uses a smaller version of the sensor. The physical properties of the lens are the same; a 50mm lens is still 50mm, but it's overall angle of view is reduced (on Canon it's reduced by 60%). So it frames more like what an 80mm lens would on a full frame camera. Really, crop factor only exist because at one point there were 35mm film camera users that were coming into the digital world, and the most affordable cameras were these APS-C "crop" cameras. So they would put an 85mm lens on to take a portrait, only to find the angle of view was now much less, that what they really needed was a 50mm lens for the same use. So crop factor was made as a way for them to know what lenses were for what functions. Now, it's still a useful thing to know, but only if you know all the old tropes, to make it easier to select the proper lenses. When Crop Factor Applies - In any case, the lens or adapter is not relevant to when it applies, it only matters if using a smaller sensor size. Any crop camera will need it's crop factor applied to all lenses that are on it, even ones made only for crop cameras. This is because the standard for measuring lenses was created for 35mm format cameras, and that standard still applies, even to the smaller format lenses, because it is an industry standard. Some feel like crop only lenses should be labeled with their crop factor applied, but the thing is, that is I think a more muddy river than it currently is. People will want to know "why is it when I use this 24mm lens (crop) it is not the same as this other 24mm lens (full frame)?" And then they now have to learn to look out for lenses that can serve a completely different function on their camera than one that they think is the same. This way, a 24mm lens works the same no matter if for crop cameras or not. Probably a lot more info than you needed LOL.

What does the control ring get you that the basic adapter doesn't do?

They both adapt the lens to the RF mount, both use the same method to do so. Both have the same performance. The only difference is the control ring adds an additional control in the form of a dial that can be programmed to do several different things. This can be anything from changing the aperture, the shutter speed, ISO, exposure compensation (what I use it for), white balance, AF mode, and so on. It can only be one at any time, and you would set it up in the menu in the same way you would customize any other control. I would say if you have the R5, R6, or R3 then it is mostly not needed, mostly just a luxury that cost an additional 100 bucks. This is because those cameras have additional controls on them that can take the place of the ring. If you have the R or RP, then it might be a good idea to get the ring since they lack in the controls the other cameras have. Or, if you just want it, that is fine too. Otherwise, your lenses will behave exactly the same. If you would like more info about the adapter, you should check out the review I have on my profile. Here is a link. https://www.amazon.com/gp/customer-reviews/R27553TB7FWPCN?ref=pf_ov_at_pdctrvw_srp

Does it work with ef-s 24mm f/2.8 stm lens?

It actually does, yes. The adapter allows the use of all EF and EF-S lenses. However, as that is a crop lens, it will place the camera into what is called "crop mode" to mimic the smaller sensor size the lens was made for. This means that only 40% of the sensor will be used, and that certain video modes will no longer be accessible. So this is more or less just a way to help users coming from the older crop systems (like the Rebel line) to the new full frame models, where unlike the EF full frame cameras you can actually use your crop lenses on them via this adapter. Older DSLR full frame cameras had a mirror that could impact the rear of the smaller lenses, and that is why they could not be used on them. The new RF models no longer have the drawback, but the lenses still have too small of a projection to fill a full frame sensor, and thus the sensor "crops" down the images to make it so it works normally. You do lose some of your resolution, 60% roughly. So 20mp becomes 8mp, 30mp becomes 12mp, and so on. While it will work, I wouldn't suggest it as a long term solution, but at some point Canon is going to release RF crop series cameras, and this lens will be just fine on those. Maybe sometime late in 2022, or early 2023. In the meantime, as long as you don't mind the crop mode, this lens will work, but if you want something that works fine without the crop mode, gives the same general framing, look at the following... EF 40mm F2.8 STM - also a pancake lens, its basically the full frame version of the 24mm, and is also pretty affordable. RF 35mm F2.8 IS STM Macro - Probably the best "cheap" 35mm lens for the RF system. Usually 500 USD new, but sometimes reduced to 400. Surprisingly good lens, and does not need the adapter to use on an RF camera, but will not work on EF cameras.

If i buy the ef eos r adapter, do i need this control ring? tia

Technically no. They are both adapters for EF lenses to the RF mount, both perform the same function and they do it the exact same. However, this adapter cost twice as much, but adds an additional adjustment dial that can be set to change an individual setting. If you have and R3, R5, or R6, it really isn't much help, since they have three control dials. If you have the R, RP, R10, or R7, then it might be worth the extra 100 USD. For more info about the control ring adapter, check out the review on my profile. Here is a link. https://www.amazon.com/gp/customer-reviews/R27553TB7FWPCN?ref=pf_ov_at_pdctrvw_srp

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Reviews

B**.

Allows use of your EF lenses on RF mount, seamless integration.

Allows use of all your EF lenses on your RF mount camera. Seamless function, no degradation of image.

15.12.2025

S**F

Top quality, must have item for me

For some reason I cannot find any third party full frame RF lenses, only for APS-C. This is the version for the latest R series cameras that not only provides access to the plethora of powerful OEM and third party full frame EF lenses, but also has a control ring like native R lenses for extra fuctionality like shortcut to changing aperture. I saw some expert YT reviews that said they tried this adapter out and successfully gives their EF lenses a second, and partly even better life. Note that there are numerous third party adapters of this kind on the market for literally a third of the price, but given the importance of this adapter working properly I rather spend the extra money to get max quality - plus, thse less expensive versions may or may not have the control ring. I can't wait to try out and buy top EF lenses that would otherwise be out of reach looking at Canon's high RF full frame lens prices they try everyone to buy.

11.01.2026

L**Z

A must have to keep using your old glass

I’ve been using the Canon EOS to RF lens converter (EF-EOS R Mount Adapter) for a several months now, and it’s been an absolute blessing. As someone with a collection of high-quality EF glass, I wasn’t ready to part with my lenses when upgrading to a mirrorless camera (and I mean buying all new mirrorless lenses to replace them would be pretty pricy). This adapter made it so I didn’t have to!! The adapter works seamlessly. There’s no noticeable loss in image quality, autofocus remains fast and accurate, and all lens functions seem to carry right over . Using the old lenses on an mirrorless is actually a bit of an unexpected treat with the advanced functions of the newer camera. The only con I have is that it adds a bit of length to the build but otherwise totally worth the reasonable price.

8.07.2025

G**S

Great build quality

Works great and ef lens fits seamlessly and adapter fits great on r mount camera

21.01.2026

L**S

Canon EF-R mount adapter

My refurb EF mount adapter looked like new and functions as designed. Shipping was very quick and expedient . A prompt and attentive seller.

23.02.2026

M**1

Must have for canon rf cameras

Nice adapter. Now I can save money on lenses without sacrificing too much if any quality. It's not that noticeable but looks good. It fits on camera perfect. The control ring is placed a little odd but still useful. I like to assign ISO to it. Saves time and money what more could you ask for?

28.11.2025

M**L

Extends the life of my EF lenses

Good adapter. Extends the life of my EF lenses that I use on my older Canons. I don't use the ring very much so when I get another one, I will get the one without the ring.

7.01.2026

J**E

Game changer!

Thanks to this adapter, I can use my EF 24mm f/1.4 lens on my Canon R50. The control ring is a game changer. I’m still learning how to take photos—the second photo was taken indoors at night with very low light.

10.01.2026

S**R

it gives me the ability to use my new Canon mirrorless camera with my old lenses set

10.05.2023

T**S

Bom preço. Cumpre bem a função

12.11.2025

K**D

الشحن سريع وقبول استرجاع المنتج رائع المنتج ممتاز جدًا واصلي ولكن لايطابق الصورة المعروضة

31.12.2023

A**Y

The adapter is very comfortable to hold, and the build quality is top notch. The ring moves very smoothly. On the EF side, I can attach any of my lenses, but on the RF side, I only have the original plastic cap for now [I haven't bought a camera yet]... ;)

10.09.2025

G**R

I have several Canon EF lenses, so this Canon Mount Adapter EF–EOS R is an absolute must-have to use them on my RF body. I upgraded from a third-party adapter — while there’s no major difference in autofocus or image quality, the Canon adapter feels more solid and reliable, with a perfect fit and finish. The control ring is especially useful on bodies like the EOS R, which have fewer customizable buttons. It adds a convenient way to adjust settings like ISO or exposure compensation on the fly. Overall, this is the recommended choice for anyone using EF lenses on an RF camera. If you’re an RF user with older glass, this adapter is the one to get.

8.10.2025

ASIN	B07H4LRRRQ
Batteries	1 Nonstandard Battery batteries required.
Best Sellers Rank	#20 in Camera Lens Adapters & Converters
Customer Reviews	4.8 4.8 out of 5 stars (1,659)
Date First Available	September 4, 2018
Is Discontinued By Manufacturer	No
Item Weight	4.6 ounces
Item model number	2972C001
Manufacturer	Canon Cameras US
Product Dimensions	2.9 x 2.9 x 0.9 inches

Canon Mount Adapter EF - EOS R, Compatible with EOS RP, EOS R, EOS R6, EOS R5

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