twosummers Loc: Melbourne Australia or Lincolnshire England

Here's a question I cannot find answered on the Internet. I have just ordered a Canon EOS R Mirrorless Camera with RF/EF lens adapter to enable me to use my EF lenses. My current camera is the EOS 6D.

I understand that Canon provide a range of lens adapters for the new R camera allowing it to use EF lenses. In my case I have just ordered the standard adapter that "comes" with the R body.

Now to the question - given that I will probably keep both cameras and would like to be able to share lenses between them. Am I restricted to buying EF lenses which will work on the R with the adapter provided OR is there an adapter that functions "the other way round" by enabling the use of the newer RF lenses on my trusty 6D?

Any users of both cameras out there with the answer?

Cheers

James

JohnH3 Loc: Auburn, AL

Following also!

bleirer

I believe it is impossible because of the sensor to flange distance, the mirror would get in the way and the rf lens could not get close enough to focus.

CHG_CANON Loc: the Windy City

Exactly. The RF mount is 20mm. The EF mount is 44mm. So, an adapter can add 24mm to enable EF lenses to sit the proper distance from the sensor to focus to infinity (focus in general) on the mirrorless RF mount. But, short of removing the mirror, there's nothing you can do to an EF-mount EOS body that can bring the RF lens to the proper 20mm distance to the sensor to enable full functionality of the RF lenses.

The flange distance (aka: flange focal distance, flange-to-film distance, flange focal depth, flange back distance , flange focal length , or register) of a lens mount system is the distance from the mounting flange (the metal ring on the camera and the rear of the lens) to the film / sensor plane.

CHG_CANON Loc: the Windy City

FYI - this is the purpose of the 'watch' link above the first post on the page.

bleirer

If you have good glass for the 6d it will look great with the R also. There are correction profiles if needed or wanted, but you won't have an issue.

Architect1776 Loc: In my mind

RF will NOT work on EF period. No further discussion needed.

amfoto1 Loc: San Jose, Calif. USA

There is no adapter to allow RF lenses to be used on an EF mount cameras. Never will be.

The reason is the "lens registers" or each mount's "flange to sensor plane" distance. This is the physical and precise distance at which a lens made for a particular mount is designed to focus it's rear image circle. This "back focus" dimension is absolutely critical to image quality.

The EOS/EF mount has approx 44mm register. The EOS/RF mount uses a 20mm register.

This difference of 24mm allows room for EF-design lenses to be adapted for use on RF-mount cameras... But DEFINITELY not the other way around. There is absolutely no room for an adapter between an RF lens and an EF camera. In fact, even if the bayonets allowed direct mounting of the RF lens onto the EF mount camera, the optical design of the RF lens would make it focus almost a full inch short of the sensor. The only ways to overcome that would be to:

1. Get out the Dremel, remove the EF DSLR's mirror and modify it's mount so that the lens fitted 24mm INSIDE the camera, or...
2. Install some hefty optics in an adapter... "corrective lenses", in a sense... which would be expensive and quite likely would ruin the image quality of the lens.

#1 ain't very practical (might as well just buy an R-series camera where Canon has already done this re-engineering for you).

With #2 the 24mm differential in this case is massive compared to some other 2, 3 or 4mm mismatches that have been partially overcome with optical adapters in other cases. "Partially" because with adapters using optics there's always some loss of image quality... or extremely high cost... or the added optics also act as a teleconverter... or all three! For example, 30+ years ago Canon briefly offered an FD/FL to EOS/EF adapter. Being that the FD/FL mount's register is 42mm and the EOS/EF mount's is 44mm, they only had to overcome a 2mm difference with optics. Canon produced a high quality adapter, but good luck finding one for under $1000, don't expect it to completely preserve the image quality of the lens and be aware that the lens focal length will change because the adapter also acts as a 1.26X teleconverter.

Now you're asking for an adapter that uses optics to overcome a 24mm differential... and that ain't gonna happen. Such an adapter would cost more than an EOS R, so there would be no sense in it.

The Canon EF lens to R-series camera adapter, on the other hand, requires no optics at all. It's just a "24mm spacer", for all practical purposes. Without that "spacer", if the EF lens were mounted directly onto an R-series camera, the lens would focus 24mm behind the camera's sensor (where the sensor is located in an EF mount camera). But there's lots and lots of room to add the adapter and no need for "corrective" optics in it. (In fact, there's so much room that Canon has designed a version of the adapter which cleverly allows use of rear filters, which should be handy with some lenses that can't use normal filters, such as the EF 11-24mm or TS-E 17mm.)

Incidentally, the same is true with the EOS M-series (APS-C mirrorless). They can use EF and EF-S lenses via an adapter without optics. But the EF-M lenses native to those cameras cannot be adapted for use on any of the DSLRs. With a lens register of 18mm, it might be physically possible to adapt EF-M lenses to an RF-mount camera... but there are so few EF-M lenses that's unlikely to happen. An RF lens would need an optical adapter to be used on an M-series camera... possible, but also unlikely because there are few RF lenses, so far.

bleirer

There are plenty of fine ef lenses to choose from that would work on both cameras with the adaptor. The adaptor is not obtrusive. The L series is somewhat affordable but good quality. https://shop.usa.canon.com/shop/en/catalog/lenses-flashes/all-lenses

chapjohn Loc: Tigard, Oregon

As stated above the distance is the issue. This is the same reason Sony/Minolta A-mount lenses can not be used with the Sony E mount cameras.

Orson Burleigh Loc: Annapolis, Maryland, USA

In EOS-world EF is the universal donor, RF the universal recipient (though only potentially so in re EF-M: It is most unlikely that anyone will ever bother to create an EF-M lens to RF mount adapter).

rehess Loc: South Bend, Indiana, USA

There are so many excellent EF-mount lenses, I am surprised you would want to have even more possibilities.