EF Teleconverters on R mount cameras-restrictions?

[olyduck]

Hi-I anticipate buying an R mount Canon in the near future and I'm trying to decide whether I also want to trade in my

EF 100-400 L (first generation).  My question is this:

If I use a Canon 1.4 or 2.0 EF teleconverter with the EF 100-400, on an R mount camera (with adapter of course), what restrictions to auto focus or other functions might I encounter?  Would those same restrictions also apply to an RF 100-500 with an RF teleconverter?

I mainly ask because, despite the great reviews for the RF 100-500, it also costs a big chunk of change. If I could retain reasonable functionality with my EF 100-400 with EF teleconverter, that would help.  On the other hand, if that combo would prohibit some of the cool functionality that an R6 (for instance) offers (like eye focus, etc.), I might spring for the RF 100-500.

Thanks for any feedback. 

[FloridaDrafter]

I use the 100-400L II with an EF 1.4x on our R6 with no issues. I bought the ring adapter, and it seems to function properly, although I haven't programed it extensively. I haven't used the RF 100-500, but I don't see why there would be any limitations other than those you normally encounter with any extender, like loss of periferal focus points, which I haven't noticed with the EF 100-400L II w/converter and adapter on the R6. But I miss stuff sometimes 😉

[Waddizzle]

What I want to know is whether or not an RF teleconverter works with the EF-RF mount adapter.  I want to buy a 2x, but don't want to spend money on one for EF mount.

[kvbarkley]

I don't see how it can. The adapter has to go right next to the camera, leaving the EF side facing the outside world.

[Waddizzle]

---

@kvbarkley wrote:

I don't see how it can. The adapter has to go right next to the camera, leaving the EF side facing the outside world.

---

Rightt, and the EF lens would go on the adapter.  

[ EOS R5 ] + [ RF 2x ] + [ RF-EF Adapter ] + [ EF mount telephoto lens ]

[ebiggs1]

I don't see why it would not work or at least mount. The IQ may be the deciding factor. Personally I wouldn't do it since I don't like adapters or 2x tel-cons.

[Waddizzle]

---

@ebiggs1 wrote:

I don't see why it would not work or at least mount. The IQ may be the deciding factor. Personally I wouldn't do it since I don't like adapters or 2x tel-cons.

---

Just as the EF 1.4x III and EF 2x III teleconverters were a significant step up over their predecessors in IQ, so are the RF teleconverters a significant  step up in image quality over their EF predecessors.  

[ebiggs1]

"... the RF teleconverters a significant  step up in image quality over their EF predecessors."

Perhaps so, but I will never know since I have no inclination to try or much less buy one.  Even if they were great IQ wise they are still another "thing" you have to deal with.  That is my biggest objection to adapters and/or a tel-con.

I have six tel-cons so it is not like I have never been exposed to using them.  In the beginning I did use them quite a bit. I found out I didn't like using them so they sit on a shelf in the formerly stop bath stained walls of my ole darkroom.

As far as adapters I have a boat load of them. They are all mostly junk.  The one exception is the Ed Mika FD-EF adapter.  It works well. I have one mounted on my FD 500mm f8 cat lens. I enjoy playing around with it.

BTW, I do not have any III versions so I have no comment on their IQ ability.

[wq9nsc]

I agree with Ernie about the 2X, I have one but it drops the IQ too much to be usable.

The 1.4X works well on better glass, I have a 200 f2, 300 and 400 f2.8, and 800 f5.6 and all of these play well with the 1.4X and produce very nice results; the first three primes are examples of Canon at the top of their game and the 800 is very good but not quite up to the stunning sharpness and clarity of its smaller brothers.  The 2X results aren't horrible UNTIL you compare the detail, contrast, and color to the bare lens results; it effectively turns some of Canon's best glass into also ran status.

Rodger

[Waddizzle]

---

@wq9nsc wrote:

I agree with Ernie about the 2X, I have one but it drops the IQ too much to be usable.

The 1.4X works well on better glass, I have a 200 f2, 300 and 400 f2.8, and 800 f5.6 and all of these play well with the 1.4X and produce very nice results; the first three primes are examples of Canon at the top of their game and the 800 is very good but not quite up to the stunning sharpness and clarity of its smaller brothers.  The 2X results aren't horrible UNTIL you compare the detail, contrast, and color to the bare lens results; it effectively turns some of Canon's best glass into also ran status.

Rodger

---

I agree with Ernie, too.  He's talking about EF Teleconvertes.   The RF Teleconverters seem to have MUCH improved optics over their EF Mark III predecessors.  Like I said, the Mark III models were a major step up, and it seems the RF models are, too.