Depth Cues

Depth perception

The ability to see objects in three-dimensions, although the images that strike the retina are two dimensional; allows us to judge distance.

Binocular cue

A depth cue, such as retinal disparity that depends on the use of two eyes. We use them to judge the distance of nearby objects 

Convergence

A cue to nearby objects distance, enabled by the brain combining retinal images. It determines depth based on how much both eyes rotate inward. Closer objects require the eyes to rotate inward more, and create greater tension to focus on the object. 

Retinal disparity

A binocular cue for perceiving depth. By comparing retinal images from the two eyes, the brain computes distance-the greater. Each retina receives a slightly different angle of the same object. Closer objects have a greater difference between what each eye sees, and father away objects have a smaller difference 

Monocular cues

• A depth cue, such as interposition or linear perspective, available to either eye alone. There are 5 monocular cues: 

  • Relative clarity 

  • Relative size

  • Texture gradient

  • Linear perspective 

  • Interposition 

Relative clarity

Objects that appear sharp, clear, and detailed are seen as closer than more hazy objects.

Relative size

If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away

Linear perspective

Parallel lines, eg. railway tracks, appear to converge as they recede into the distance

Interposition

Objects that occlude (block) other objects tend to be perceived as closer

Texture gradient

Progressive change from coarse to fine texture of surfaces with distance provides depth (distance) information