I found this document online, referring to older Canon EOS-1 cameras, about how the EOS AI-Servo predictive auto-focus works.


It is fully expected that the first frame of any moving subject is OOF, regardless of how long you track the subject with the shutter half-pressed. Prediction only kicks in, incontinuousmode, after the first shot has been taken, which isn't exactly what I expected... I expected that if I track for a second or two, it should be fine in 1 shot mode. Nope.


The document also confirms that it does track acceleration as well as velocity, which was something I wondered about.


It would be nice if Canon had dedicated a sentence or two of their manual to how the predictive focus functions are supposed to work. It doesn't matter how advanced their focus system is if the majority of their customers don't know how to take advantage of it.


Link to document