AF on 24-70mm f4 won't "Lock"

[tmalleman]

Hi Forum,

I've been using the same 24-70mm f4 Canon lense for about  five years. A couple months ago, the Auto Focus stopped "holding" or "locking" when I re-composed. As always, I focus on the area of most interest, then hold the exposure button halfway down while I do my re-composing––but lately that original focus won't stay put. It skitters over to whatever is in the middle of the frame...

Any advise or insights about this?

Thanks,

THOMSA ALLEMAN

Los Angeles   

[MikeSowsun]

Check you AF mode. It should be "One Shot" not "AI Servo"  or "AI Focus". Those other two modes cause the AF to behave like you have described.   

[ebiggs1]

Otherwise do a full reset of your camera. Menus, tools, clear all settings and all custom settings. This is the best thing to do when thing don't go as you expect.  You could inadvertently set something incorrectly.