What is eye-control focus (ECF)?
Eye-control focus is a technology unique to Canon that lets the camera track what you re looking at in the viewfinder so it can select the nearest focus point automatically. ECF works as follows. A series of tiny infrared LEDs (light emitting diodes) shine harmless infrared energy onto your eyeball as you peer through the viewfinder. Light sensors record the infrared reflecting off your eye and calculate the focus point. A computer in the camera then examines this data and decides which of the focus points is closest to that point and selects it. If the camera is in AI Servo mode then it will also adjust focus automatically based on that selected point. ECF is thus a very complex technology which involves a lot of different factors. And, needless to say, it works well for some people and not well at all for others. Each ECF-capable camera must be calibrated for each user, but even thorough calibration (you need to run through calibration at least a half dozen times or more before thing
