Canon RF 2x work with EF-RF adaptor

[PurpleAnts]

Hi, I try to play some telegragh with a 70-210 ES lens on EOS R. I am currently using a EF-RF adaptor to mount the EF lens to EOS R. Can I add a RF 2x mount between the R5 and EF-RF adaptor and make the lens to 400mm? Thank you.

[p4pictures · Accepted solution]

Unfortunately this nice idea doesn’t work. Physically the inside dimensions of the EF to EOS R mount adapter do not allow the protruding front part of either the RF 2x or the RF 1.4x to fit inside. I have tried this myself last year so I know it to be true. 

[kvbarkley · Accepted solution]

Ken Rockwell did it with an R and EF100-400 with the 1.4 *and* 2.0 converter!

https://kenrockwell.com/canon/eos-r/r.htm

[p4pictures · Accepted solution]

Unfortunately this nice idea doesn’t work. Physically the inside dimensions of the EF to EOS R mount adapter do not allow the protruding front part of either the RF 2x or the RF 1.4x to fit inside. I have tried this myself last year so I know it to be true. 

[p4pictures]

Just found these pictures I took from when I tried to make this work.

This is Extender RF 1.4x and the EF to EOS R control ring mount adapter, though it is also the same for the plain adapter without control ring.

[ebiggs1]

"Can I add a RF 2x mount between the R5 and EF-RF adaptor ..."

Whether that will work or not I don't know since I have never tried it. However, if it doesn't fit you could try one of the off brand tel-cons from Kenko, Tamron or Sigma. Personally I am not a fan of any tel-con but that said I have about a dozen of them. I know, I know its just curiosity but it has confirmed my basic dislike for a tel-con.

There are a few, very few, lenses where the combo does work well together, IMHO. The ef 70-200mm f2.8 lens is one of them but with the 1.4x model and not the 2x. As a matter of fact I don't consider the 2x to be of any use on any lens. I have used the Sigma 1.4x on my Sigma 150-600mm S lens and it works fairly well as it does on my 120-300mm Sigma f2.8 lens.

The Kenko seems to be as good as an off brand generic tel-con can be. No where as good as the Canon model or even as good as Tamron or Sigma but it m ay do what you want.

[kvbarkley · Accepted solution]

Ken Rockwell did it with an R and EF100-400 with the 1.4 *and* 2.0 converter!

https://kenrockwell.com/canon/eos-r/r.htm

[p4pictures · Accepted solution]

I often use the EF 70-200mm f/2.8L IS II USM with an Extender EF 1.4x III on the EF to EOS R mount adapter with my EOS R cameras and also with the EF 100-400mm f/4.5-5.6L IS II USM. 

When I had the 1.4x and 2x RF extenders last year I thought that mounting the EF EOS R adapter on them would allow the extender to be used with all kinds of EF lenses, but it was obvious that they physically don't fit.

[PurpleAnts]

Thank you guys. Seems EF lens + EF extender + RF converter works while EF lens + RF coverter + RF extender doen't. I will pursue the fist path and give it a try.