I want to take self portraits with the 5D2 (or 50d - they are similar). The Live View with face detect option in servo mode will identify a face if it's not too far off center and focus on it. But the problem is it can be activated, as far as I know, only with the AF-ON button. The button has to be held down for a few seconds while it hunts around and zeroes in on the face. This is not a problem if I am taking a picture of someone else. But is there a way to trigger it via the shutter release ? That way I can set the timer and stand in front of the camera and after the timer has counted down, it will focus (on the face) and take the picture.