Weird problem with 6D+100-400L II + 1.4x III=no AF

[mangobutter]

For some reason, only "MF" appears on my 6D top LCD, no AF activation on shutter. No attempt to focus. Tried mounting TC on lens, THEN on camera. Also tried mounting on BODY first, then lens. Still same. Same exact 100-400L II + 1.4x III transferred over to my EOS R and suddenly everything works perfectly. All switches in the proper position. Tried another lens on the 1.4x III + 6D and AF is working. So it's just the particular combo of the 100-400L II + 1.4x III + 6D where AF doesn't work. And yes I dismounted each individual piece and re-mounted until firm click multiple times. Any ideas? Cycled 6D on and off etc. The 100-400L II works perfectly on my Fuji bodies as well w/ and w/o the 1.4x III. Strange quirk with the 6D.

 

[neuroanatomist]

Durp, deleted my prior post because of course @P-visie is correct. I read R6, not 6D. The 6DII supports f/8 AF, the original 6D does not.

The 1-series supported it all along, except that a firmware update to the 1D X was required (after some complaints from pros, suspect). The 5DIII, 6DII, and other post-2013 cameras supported f/8 AF often with multiple AF points and the feature made its way down the lines.

 

[P-visie]

According to this table on shuttermuse, the 6D AF does not work with f8 (EF 100-400mm II f5.6 + 1.4 extender = f8).

 

[mangobutter]

Interesting. I sort of thought it had to do something with that but i thought i'd at least be able to use central point. Shucks, so no AF at ALL when using the 1.4x III. Good to know nothing wrong with my 6D. Thanks

 

[neuroanatomist]

Shucks, so no AF at ALL when using the 1.4x III.

You can AF with the combination in Live View. It’s slow, but it works. Live view works at f/11 with the 2x TC as well.