Eye control focus (ECF)
From The Glossary of Digital Photography
A technology developed by Canon that enables the camera to know where the photographer's eye is looking and select that point to focus on. The viewfinder uses a group of very small infrared LEDs to bounce infrared light off of the photographer's eyeball to determine which way he or she is looking. It then selects the closest focus point in the automatic focus system and activates it. The system has to be trained by each user to calibrate it. Even then, it is not 100% accurate, but each version is improving in reliability and speed.
