How do we know how near or far objects are? 

In today’s session, Cogitanian’s learned about two types of visual cues: binocular cues and monocular cues.

Binocular Cues are distance cues requiring the use of two eyes.

1. Retinal Disparity – The slightly different view two eyes have of the same object. The degree of disparity decreases with distance. Ex: Moving one finger in front of your face, seeing double’ when it’s closer and seeing one finger when it’s further away.
2. Convergence – The inward turning of the eyes that occurs when an object is viewed up close. The closer the object, the greater the degree of convergence. Ex: Becoming ‘cross eyed’ when trying to look at the tip of your nose.

Monocular Cues are distance cues requiring the use of one eye.

1. Linear Perspective - When parallel lines appear to merge together at a single point on the horizon.
2. Relative Height (Elevation) - When objects near the horizon are perceived as being farther away and objects away from the horizon are perceived as being closer.
3. Relative Size - When the closer of two same-sized objects appears bigger than the one farther away. Only applies to familiar objects.
4. Interposition (Occlusion) - When objects overlap, the obstructed object(s) is perceived as being farther away than the object(s) in front of it.
5. Relative Brightness - When the closer of two identical objects appears to reflect more light.
6. Aerial Perspective (Haze) - When objects are at a distance have less contrast, less color saturation, and appear hazy than closer objects. This is due to light being scattered by the atmosphere.
7. Texture Gradient - When closer objects have more detail and texture than objects that are farther away.
8. Motion Parallax - When objects that are closer appear to be moving faster than objects that are further away.

We finished our session by looking at a series of images (a photograph, a painting, and a still image from an animated cartoon series) and identifying the monocular depth cues in each.