1. A method for controlling a first camera by estimating the angular deviation between a person gaze direction and a digital camera line of sight, for use with a device including a first digital camera having a first center line of sight and a second digital camera having a second center line of sight that is parallel and opposing the first center line of sight, the method comprising the steps of: capturing an image to an image file by the second digital camera; detecting a human face in the image by using a face detection algorithm; estimating an angular deviation α between the second center line of sight and an imaginary line from the second camera to the detected human face based on the captured image; estimating an angular deviation β between the imaginary line from the second camera to the detected face and the human face gaze direction based on the captured image; estimating an angular deviation φ between the first center line of sight and the human face gaze direction based on the estimated angular deviation α and the estimated angular deviation β; and initiating, controlling, stopping, or inhibiting an action is response to the value of the estimated angular deviation φ.