Dr. Joel Germond Loc: California Central Coast

Before I return the Canon RF 600 mm lens I just bought I'm wondering if there is a way to mount it on my EOS 5D Mark IV, and if there are drawbacks for doing so. I see there are lots of adapters available to attach EF lenses to RF camera bodies, but not the other way around (adapters for EF camera to RF lens). Is there a technical reason for this? Will that lens even work properly on a 5D mark IV? Your expertise and technical advice is appreciated.

BB4A

RF lenses have more pin connections than my 5D Mark IV bodies, so I don’t see any sensible option for building an RF lens to EF body adapter. Logically at least 2 or more functions of the lens wouldn’t be supported by the body. That probably explains why that combination isn’t being offered by Canon.

I have to say that I’m very happy with my EF lens to RF body adaptor; operations with my R5 body and all of my EF lenses have been absolutely seamless. I have the programmable ring adaptor, which gives me flexible programming options; very useful & essentially upgrades my EF lenses to RF operating standard.

Edit: Before you send your RF lens back, have you considered buying an EOS R body to mount that lens on? A very capable camera, and Canon is currently offering an attractive sale for refurbished R’s: https://www.usa.canon.com/shop/p/refurbished-eos-r-body?utm_source=google&utm_medium=Product_Search&utm_campaign=Google_Product_Feed&gclid=CjwKCAjwrdmhBhBBEiwA4Hx5g01YQwmvdxG0A1bZ0eLJwwXf-5S_s3NN2SllOrTV5yOOG1vEqPMiNRoCifYQAvD_BwE&gclsrc=aw.ds

CHG_CANON Loc: the Windy City

The removal of the mirror places the RF mount 24mm closer to the sensor. All other technical issues aside, there is no way to retain infinity focus for an RF lens mounted further than the 20mm flange distance of the RF mount. Although the flange distances differ across vendors, no mirrorless lens will work on a DSLR. But in all cases, the legacy film / DSLR lenses can be adapted to mirrorless bodies, without regard to vendor / mount, as there's around 20mm free space for various vendors to introduce the mount adapter. Whether the legacy SLR/DSLR lens retains AF and aperture control depends on specifics of the lens, the target mirrorless body, and the capabilities of the mount adapter. Some will retain all functions, others will revert from AF to MF. Closer attention to the technical details will be needed to avoid such compatibility problems.

BB4A

Excellent point, I’d forgotten about the physical space problem.

Architect1776 Loc: In my mind

Just curious, why returning?

Ednsb Loc: Santa Barbara

Great answer

PHRubin Loc: Nashville TN USA

As CHG_CANON pointed out, removing the mirror allows camera designers to make the camera smaller with the lens closer to the sensor than on a DSLR. There is no way to mount an RF lens close enough to the sensor on a DSLR.

EDIT: But you can make a DSLR lens further away on a mirrorless, hence the adapter.

foathog Loc: Greensboro, NC

It's possible he made a big boo boo.