Our perception of objects is far more constant or stable than our retinal images. Retinal images change with the movement of the eye, the head and our position, together with changing light. If we relied only on the retinal images for visual perception we would always be conscious of people growing physically bigger when they come closer, objects changing their shapes whenever we moved, and colours changing with every shift of lighting condition. Counteracting the chaos of constant change in retinal images, the visual properties of the object tend to remain

constant in consciousness. We are not usually conscious of people appearing to get bigger as they approached us or of the things appearing to change the shape according to the angles from which we view them. In relation to visual perception, key "consistencies" are site, shape, lightness and colour.