Canon cameras have several ways of deciding where to focus (these have to do with the focus spots), and two ways of deciding how to focus.
You call the latter “focus modes”, and there are two: “One Shot” and “AI Servo”.
- One Shot means that the focus locks (you hear a beep and as long as you keep your finger on the shutter, that distance remains locked.
- “AI” is A I, as in “Artificial Intelligence”, not “Al” as in “Alan”; and a servo motor is a closely controllled motor with feedback loop. So that mode just means “continuous focus”.
One Shot is for static subjects. AI Servo is for moving subjects,like these:
I shot that yesterday, for the local newspaper. So since the young lady would not stand still, I had set my camera to AI Servo mode.