Back button focusing with the 6D

Question

I cannot get my 6D's back button focus (AF-ON) to work.  After following directions on Canon's website on how to set it up, the button just does not do anything.  Auto focus only works  with the shutter button.  I have the function set to "P" which I understood to be o.k.  Would resetting the camera to factory default help?  I would prefer not to have to send the camera to Canon for a one button repair.  The camera body was purchased new and is still under warranty.
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Answer 1

It's super easy to set up BBF on a 6D....
If you have already been changing some things and are unsure which ones, you might want to reset all the Custom Functions to factory default, before starting. (Note: There is a way to view which C.Fns are set and to what each is assigned... As you enter each of the four C.Fn groups, note the list in the lower LH corner of the LCD screen, that shows all the C.Fns in that group at a glance. The top line is the C.Fn number, the bottom line is the setting for each C.Fn.)
To set up BBF....
All you have to do is go into the menu, Custom Functions, C.Fn III-5, operations/others, button assignments. Select and enter that and then press "set" and this should take you right to the top of the LH column, which is a graphic illustration of the shutter release button. Press set again to enter this, then scroll to select the center option "start metering" and press "set" once more to select this choice, then press "menu" button several times to back out of the menus. Done!
What this does is remove AF start from the shutter release button.  By default it's already assigned to the AF-On button on the back of the camera too, so BBF is set up and ready to use as soon as you remove it from the shutter release button.
Metering and Image Stabilization will continue to start with a half press of the shutter release button or whenever you press the AF-On button. But AF will  only start with your thumb on the AF-On button. Using BBF, you now can use AI Servo most of the time, for stationary or moving subjects. If you want to "focus and recompose", simply focus and then lift your thumb off the AF-On button to leave focus where it is and recompose as you see fit. (Without BBF, you cannot do focus and recompose.... it will cause mis-focused shots.) You still might want to switch back to One Shot when you want high precision focus with stationary subjects.
There is another option you may want to consider...
Using the same Custom Function III-5, if you prefer you can swap the functions of the AF-On and * (AE Lock) buttons. I do this on my cameras for a couple reasons: One is that the * button is larger, more prominent, and closer to my thumb... so I prefer to use it for focusing. The other reason is that older Canon models that didn't have the AF-On button, you had to use the * button and that's the way I learned to use BBF (Note: In some cases there was an AF-On button on the body but not on the vertical grip, while older cameras simply didn't have an AF-On button at all, on the body or the grip).
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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