On R5/R6 EF-100-400 L IS II + 2X TC III could be a reality

Based on the focussing speed of the 800mm f/11 on R5 (or R6), it seems the day of EF 100-400 L IS II w/ 2x TC III may change.
Would that be usable for BIF? or will that cripple the AF speed (as it does with DSLR)?
Those who have this combination at hand, please post your experience with that combo.

rndman wrote in post #19104984
Based on the focussing speed of the 800mm f/11 on R5 (or R6), it seems the day of EF 100-400 L IS II w/ 2x TC III may change.
Would that be usable for BIF? or will that cripple the AF speed (as it does with DSLR)?
Those who have this combination at hand, please post your experience with that combo.

As soon as I get my R5 that lens will be one of the first I will try. I do have both 1.4x and 2x extenders. But since I also have 200-400 I think the 100-400+2x will be limited use for me but will test it out just to see.

rndman wrote in post #19104984
Based on the focussing speed of the 800mm f/11 on R5 (or R6), it seems the day of EF 100-400 L IS II w/ 2x TC III may change.
Would that be usable for BIF? or will that cripple the AF speed (as it does with DSLR)?
Those who have this combination at hand, please post your experience with that combo.

Af workd fine with the EF 100-400L II with Extender 2.0x III on the EOS R, IME anyway, so I see no reason why it would not work even better on the R5 or R6.

I do not know whether you would be entirely happy with IQ, however. I found that close to MFD the images becoem a little mushy, for my taste anyway. Contrast dimishes close to MFD with that combination.

HTH, kind regards, Wim

wimg wrote in post #19105102
Af workd fine with the EF 100-400L II with Extender 2.0x III on the EOS R, IME anyway, so I see no reason why it would not work even better on the R5 or R6.

I do not know whether you would be entirely happy with IQ, however. I found that close to MFD the images becoem a little mushy, for my taste anyway. Contrast dimishes close to MFD with that combination.

HTH, kind regards, Wim

When used with 2x TC on 100-400, I assume it is mostly for the reach. So the MFD situation would be rare.
Based on what you state, beyond MFD there should be no issue in IQ.
The only thing could be the AF speed (especially the usability of that combo for BIF). And that what I am interested to know how it performs.

rndman wrote in post #19105244
When used with 2x TC on 100-400, I assume it is mostly for the reach. So the MFD situation would be rare.
Based on what you state, beyond MFD there should be no issue in IQ.
The only thing could be the AF speed (especially the usability of that combo for BIF). And that what I am interested to know how it performs.

Unfortunately, BIF is something I do not do, so I can't help you there - landscapes, yes, but I never had the need to go beyond the 1.4x extender there - and that just works liek a charm .

Kind regards, Wim