Binocular cues. A. Drag the red disc and watch the eyes converge to keep its image centered on the retinas. Convergence reflects the absolute distance of the object from the eye. This cue is useful for objects less than a meter away. B. Add another disc and drag it back and forth. The blue disc is slighly offset from the red disc on the retina. That offset, the binocular disparity, reflects the relative distance between two objects. When the blue disc is closer than the red one, its image projects to the outer (temporal) part of the retina; when it is farther away, it projects to the inner (nasal) part of the retina. Binocular disparity is useful for objects up to about 30 meters away. (The eyes in the diagram, and the distance between them, are approximately actual size.)