I've taken these shots today (more than 80) and the results were out of focus shots when shooting in a frontal position, ie when subject is coming towards me. I'm using both AL Servo and single shots (shutter speed 1/400,1/500) without any success. Side shots are OK except those that I shook the camera.
By looking at these shots,
1) Do I have a problem lens.
2) Camera processor slow, could not keep up with subject's approach speed to send to lens for focusing.
3) Human error.
Thanks in advance for your feedback, Bernard