AI Servo/issues with AF

[MarcusM]

I have a Canon 300D and both my old 18-55mm kit lens and my new 50mm f/1.4 lens seem to "hunt" when using AF even after I depress the shutter release halfway to engage the focus lock.

Someone told me that it might be because AI Servo is on, but I looked in my instruction manual and it looks to me like AI Servo is only on in the Sports mode - I only use Manual and it doesn't even look like I have the option to turn it on or off in Manual.

Which leaves me with the question, why does my lens seem to try to focus (only occasionally) after I have depressed the shutter halfway to lock the focus? Doesn't "lock" the focus really mean to lock it no matter how far from the original position I move my camera?

 

[keith204]

Check your AF-selection point... is your camera set to single-point AF select? If so, which one? If you're set to single-point select, and you're depressing the button when that point isn't on any points of contrast, then your AF will hunt...

Try setting your camera to use all 5 AF points, and see if that fixes the problem. Make sense?