Traditionally, the human eye is perceived as being "just" a camera, that renders an accurate, although limited, image for processing in the brain. This interpretation probably stems from the apparent similarity between a video- or photo-camera and a human eye with respect to the lens, the iris and the focal length control. By analogy this similarity is extended to the image detection element, i.e. the human retina is assumed to basically have the same function as a CCD-detector or film