topic Re: Using RF Teleconverter with EF lenses in EF & RF Lenses

Using RF Teleconverter with EF lenses

Mangalmurti — Mon, 06 Oct 2025 17:23:27 GMT

I have an R6, can i attach a 2x RF teleconverter, then an EF-RF converter ring, and then an EF lens, and have it function well?

Re: Using RF Teleconverter with EF lenses

p4pictures — Mon, 06 Oct 2025 17:41:48 GMT

No this is not possible since the protruding front part of the RF teleconverter will not fit inside the EF to RF mount adapter. I know this as I tried it myself in the past.

Re: Using RF Teleconverter with EF lenses

deebatman316 — Mon, 06 Oct 2025 17:41:57 GMT

No it will NOT work this is by design. RF Mount teleconverters cannot be attached to any of the EF-RF Mount adapters. The only way this is going to work is EF-RF Mount Adapter > EF Mount Teleconverter > EF Mount lens compatible with teleconverters. So DO NOT attempt this the RF Mount teleconverter won’t mount at all to the mount adapter.

Re: Using RF Teleconverter with EF lenses

VAH1979 — Wed, 22 Jul 2026 02:31:09 GMT

I have the Canon R6 Mk2 along with the EF Rf adapter. Now, is it possible to use an ef teleconverter with ef lenses in the pattern:

R6 Mk2-Ef/Rf adapter-ef teleconverter-ef lens

and would this work? At a vistek here in Canada, the salesperson told me that this concept wouldn't work bc I'd be attaching the teleconverter to the adapter which increases the focal length or something.

Re: Using RF Teleconverter with EF lenses

deebatman316 — Wed, 22 Jul 2026 03:26:00 GMT

@VAH1979 The EF-RF Mount adapter works with EF Teleconverters. Teleconverters do change the focal length and the amount of light entering the lens. For instance a 2x Teleconverter you loose 2 stops of light. But in return your focal length was multiplied by 2. If they’re talking about loosing focus to infinity that’s not true. The Mount adapter puts the EF/ EF-S lens at the correct distance from the image sensor. So basically it acts as a mirror box like in a DSLR. The Mount adapter has communication pins in it and passes along the communication from the camera to the lens. The only way it will work is body > EF-RF Mount Adapter > teleconverter > lens. Canon brand Teleconverters only work with certain lenses. This is because they protrude into the lens that’s mounted.

Re: Using RF Teleconverter with EF lenses

kvbarkley — Wed, 22 Jul 2026 11:58:11 GMT

Look what Ken Rockwell did, and it worked!

Re: Using RF Teleconverter with EF lenses

ebiggs1 — Wed, 22 Jul 2026 14:51:18 GMT

"I'd be attaching the teleconverter to the adapter which increases the focal length or something."

The RF to EF adapter simply corrects mismatch of distance from focal plane between the two lens types.

A tel-con on the other hand magnifies a portion of your image circle thus narrowing the field of view. The true FL does not change. There is always a penalty to pay for this. Distortion will be increased. CA will be increased. IQ will suffer and you lose some f-ratio. You may lose some AF function or at least make it less effective.

Re: Using RF Teleconverter with EF lenses

ebiggs1 — Wed, 22 Jul 2026 14:52:37 GMT

"Look what Ken Rockwell did, and it worked!"

Ken Rockwell has certainly found a friend in you!

Re: Using RF Teleconverter with EF lenses

MarkL — Thu, 30 Jul 2026 23:44:14 GMT

I'm looking to mount the EF 100-400mm F4.5-5.6L IS USM lens to my R10 body with a lens extender. I already have the EF to R adapter (not the control ring adapter) for use with my other EF lenses. Can I buy the EF1.4x or the EF2x and mount it between the lens and the adapter? It looks like the exact set-up that's in your picture, minus one extender. I'm curious; why do you mount two extenders to your camera.

Re: Using RF Teleconverter with EF lenses

kvbarkley — Fri, 31 Jul 2026 00:28:46 GMT

I don’t. The picture is from Ken Rockwell from when the R was new. He was just showing that it could still focus at really small apertures.