Mount Adapter EF-EOS R compatibility with EF 1.4X Extender II

[Steve07]

I have an R5 mkI and the R to EF adapter. I have a 70-200 f4 L IS ll usm lens. My question is I am considering purchasing the EF 1.4x ll extender, will this combination work. The lens works beautifully with the R5 and its canon adapter. 

[kvbarkley]

Ken Rockwell got it to work with an R:

[Steve07]

Hi Ken, your picture shows both the 2x and the 1.4x converters connected. Does this actually work. I thought I had read that the 2x only works at f8 (I may be wrong) but that’s pretty impressive if they work both connected together. 

[johnrmoyer]

---

@Steve07 wrote:

Hi Ken, your picture shows both the 2x and the 1.4x converters connected. Does this actually work. I thought I had read that the 2x only works at f8 (I may be wrong) but that’s pretty impressive if they work both connected together. 

---

does it work? might depend upon definition of work. I have experimented with stacked extenders. EOS R5 seems to me to have some difficulty with autofocus when F Number is larger than 22, but I have done autofocus at F/45 as an experiment. Butterflies were hand held in bright sunlight. My EOS 80D will autofocus in live view mode at F/11 even though it is documented to only autofocus to F/8. The EOS R5 is always in live view mode because it has no mirror. Stacked extenders give enough additional pixels on small bird 400 meters distant to determine species and document sighting.

There will be a very small aperture with resulting small aperture diffraction blur

There will be a very shallow depth of field

It is difficult to get a fast enough shutter speed

Stacked extenders increase magnification without increasing minimum focus distance

This photo was made with EOS R5 and stacked extenders

EOS R5 ; F/18 ; 1/166 sec ; 1120mm ; handheld ; distance 3.9 meters ; EF100-400mm f/4.5-5.6L IS II USM +1.4x III + Kenko TELEPLUS HD C-AF 2X DGX

https://www.rsok.com/~jrm/2022Oct07_birds_and_cats/2022oct05_monarch_IMG_0672c.html 

and this one at 2.25 meters distance https://www.rsok.com/~jrm/2022Oct07_birds_and_cats/2022oct05_monarch_IMG_0664c.html 

Monarch Butterfly (Danaus plexippus) on Zinnia in Norman, Oklahoma, October 5, 2022

[kvbarkley]

I am taking Ken Rockwell's word for it:

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

The aperture limit only applies to a AF-chip based DSLR. The idea is that there is no aperture limit with on-sensor phase detect.

[Steve07]

Many thanks, very useful link.