How do I lock single AF points on the 5D3?

[rugfoot]

How do I lock a single AF point on the 5D3? I know how to move it around, but when I choose a place and press the shutter halfway, the point moves and finds something else nearby in the frame. Is it possible to lock it so that it doesn't move around?

[ebiggs1]

Press the upper right button. The joystick is used to move the AF point around the frame, Then press set.

[rugfoot]

Thanks a million for that. I was missing the "set" button. Really useful - and to the point. Richard

[TCampbell]

The focusing system on the 5D III is very advanced.  Canon has a 47 page guide that explains the various features of the system.

You can find it here:  http://www.learn.usa.canon.com/resources/articles/2012/1dx_guidebook.shtml

I suspect you may be using the zone AF mode.  The AF point selection modes are:

Spot AF:  This is a reduced size spot... minimal area.  It's designed when you want the smallest/tightest possible area to focus.  For example... the iris of someone's eye.  The target needs to have good contrast and pattern detail.  But this mode might be used when there is something nearby at a different focus distance (for example... someone's eyebrow).  If you want the camera to lock focus on the "eye" and not be distracted by the fact that the "eye brow" is a little closer, then you can use this spot AF mode to really reduce the size of the focus target.

1 pt AF:  This is the standard single point AF mode (not reduced spot, but not expanded spot either.)

Expanded AF area:  This uses points left/right and above/below.  This mode is intended for situations where the "spot" doesn't have good contrast or adequate pattern so it may struggle to get a focus lock.  By expanded and taking assistance from nearby points, the camera has an easier time locking focus PROVIDED that the expanded area points are all at the same distance.

Exapanded AF area: Surround:  This is similar to Expanded AF area but also uses the corners as well (not just above/below/left/right points.)

Zone AF:  This is sort of like a mini-version of auto-select except the auto-select is restricted to a limited area (zone).  You can drive these points around with the joystick, but recognize it's not forced to use just one main point... it can use any point as long as it's in that "zone".  It's nice for shooting when your subject isn't necessarily in the frame when you plan the shot, but you know where you plan to place that subject.    

Auto 61 pt AF:  This mode allows the camera to use any point and you don't get to pick it.  BUT... the Canon EOS iTR (intelligent Tracking & Recognition system) will follow your subject all around the screen.  The guide that I linked above (actually that's just the page that introduces it... the actual PDF download is in the lower left corner of that page) explains all the tuneable options of the iTR system.

I'm wondering if you weren't using the Zone AF - in which you can drive the zone around with the joystick but the camera gets to choose any point it wants within that zone.

[rugfoot]

Thanks for that Tim - really useful. I seem to have worked it out now! Richard