EOS 7D autofocus doesn't hold target

[stockdizzle]

Noob here.  I've read the manual and checked Google as much as I can, but I'm unable to solve this simple problem.  Just bought a used 7D and can't seem to figure out how to have it stay locked on a target as I recompose the shot.  When I half-depress the shutter button it focuses, but when I move the target it changes focus to whatever else was in that focal area.  I've tried going into 'C.FnIII: Autofocus / Drive' (sub menu 6) and checked (enabled) all the options (both the square box, and bullseyed square box on right), but it still isn't locking focus.  Phase Detection is enabled.  What am I doing wrong here?  It is my understanding that the bulleyed square targets are cross-type sensors (Canon's more advanced, precise focusing technology), and that was my initial intent--to be able to select a focal point, lock it, then recenter and compose the shot.  Please help--thanks!

Canon EOS 7D (original--not Mark anything)

Canon EF 85mm f/1.8 telephoto lens

[cicopo]

Bob beat me to it but I'm thinking it's not set to ONE SHOT. Servo mode won't lock because it expects a moving target.

[stockdizzle]

Thanks for the reply. It was and always has been on ONE SHOT throughout this issue, assuming that if it displays "ONE SHOT" on the display during operation then it is in-fact in ONE SHOT mode (without other steps/possible mode settings).  This is why I'm nervous as to either my noobism or the internal condition of the camera. I'm wondering if there really could be such a software glitch though. Thoughts on that?

[stockdizzle · Accepted solution]

Haha, well no wonder!  Apparently in AV mode it will not take a picture if it is not in focus lock...  

Problem solved!  Thanks everyone.  🙂