AF issues with 600 and 400 MK III

[Dholai]

Please tell me what am I doing wrong.
I just upgraded from the MK II versions of these (600F4 and 400 F2.8)
Both the lenses on 1DxMKII will not AF at all when changing focusing from a near to a far point. e.g. If I am focused at 20 ft-trying to focus at 200 ft or at infinity does not work- the camera will simply not focus. Even rotating the barrel manually does not do any good.
OTOH- if I go from, say, 20-50-100-200 ft to infinity - it will focus but that too is inconsistent. sometimes no matter what I do- nothing , I repeat, nothing at any distance will be in focus.
I keep the AF-ON or the shutter half pushed. Makes no difference.
Even on manual focus- rotating the focusing barrel does not change focus promptly- it rotates on and on- reminds me of 85 mm 1.2L

Never had these issues with the old lenses.
Called Canon - could not give me a solution. Tried their recommendations- no result.
I am sure the fault lies with me. What am I doing wrong- what am I expecting wrong?

Please help. Thanks.

 

[ethanz]

Have you tried a different body to see if that changes the AF?

 

[Dholai]

Yes Ethanz, I did. Tried on a 5DMK IV and a 5DsR. Same result.

 

[ethanz]

I don't remember where you live, but maybe you could get a loaner from CPS and see if that exhibits the same behavior as your lens?

 

[Dholai]

. In Atlanta Ethan. Thinking to return and exchange them. Just curious to hear if anybody else had the same issues

 

[Dholai]

Based on another tech savvy photographer's suggestion- I did reset all functions in both cameras and now- both lenses work like a charm. All issues solved. But that brings up the million dollar question- what setting caused the fault and will it come back when I reload my settings?
I guess I just have to try and see
Any idea anybody ? Please ??

 

[Viggo]

Only thing I can think of is that function where you can tell the camera to not continue to try and focus if focus can’t be achieved. You can either tell it to keep trying or simply stop.