vorlon1 wrote in post #15427609
If the shutter button is held down for continuous shooting, whether AI Servo AF will always take time to ensure correct focus for each shot (which may result in slowing down the drive speed), or whether the camera will always fire at top fps speed (even if proper focus cannot be ensured for each shot in the sequence).
This isn't 100% true.
In release priority, the camera will make one focus measurement, evaluation and lens drive cycle, and that's it. If the subject is an easy target, this will be enough, the image taken will be in focus and the drive speed will be maintained, as there is time allocated for this focusing operation in between the shots.
If the subject is difficult, the camera may drive the lens to the wrong distance setting, or fail to drive the lens at all, if the camera is utterly confused. The image will be out of focus, but it will still be taken, at the claimed frame rate.
This is exactly as described in the quote. However, when set to AF priority, the camera will make one or more attempts at measuring, evaluating and driving the lens to achieve proper focus. Exactly how many Canon does not disclose. But the important thing to understand is that this is a finite number. After a couple of attempts, which will take enough time to slow down the frame rate, the picture will be taken, regardless of if focusing still has not been accomplished successfully.
Thus when using Servo AF, there's no setting which will ensure that every image is properly focused. It's only when using One Shot AF a 7D will refuse to take a picture if it's out of focus. If the picture is taken, the camera is convinced it's focused. It may have focused on something else than what you intended it to, or it may be completely fooled and not focused at all, but at least it thinks the image is in focus.