Human EyeballVisual Perception

Stereopsis (Contralateral Shift)

Color Range

Trichromatic Color

• http://lite.bu.edu/vision/applets/Color/Addition/Addition.html

Visual Perception

1. Figure/Ground Dynamic

• The ability to distinguish different objects from one another

• Analyzing separate information allows us to re-act to each individual object accordingly– Camouflage – when figures blend into the

background

Figure-Ground Dynamic

Camouflage

Gestalt Rules

–Gestalt Psychologists focused on how we normally perceive images as groups, not isolated elements

–Several factors influence how we will group objects:• Proximity• Similarity• Continuity• Closure

2. Proximity

• When objects are close together we tend to perceive them as together rather than separate

Proximity

Proximity

Proximity

Proximity

3. Similarity

• Objects that are similar in appearance are more likely to be perceived as belonging in the same group

Similarity

Proximity and Similarity

4. Closure

• The tendency to overlook incompleteness, and complete objects so that they fit into our mental preconceptions of what objects are supposed to look like

Closure

5. Continuity

• To perceive lines and motion in fluid forms rather than jagged motions

Continuation

Constancy• Constancy refers to our ability to maintain

a constant perception of an object despite its relative changes in angle, lighting, distance, etc. to us There are three types of constancy cues:– Size Constancy– Shape Constancy– Brightness Constancy

6. Size Constancy

• Objects closer to us will produce bigger images on our retinas, and as they move away they project a smaller image. The actual size of the object does not change.– IE. When a man is right in front of us, he

is 6 ft. tall. As he walk further and further away, his image gets smaller. He hasn’t shrunk; he is still 6 ft. tall.

Size Constancy

7. Shape Constancy

• Objects viewed from different angles will produce different shapes on our retina. Though we may change our position, the shape doesn’t change. – IE. Looking at the top of a glass one

way makes it look round; from another angle it looks elliptical. The actual shape hasn’t changed…it is still round.

8. Brightness Constancy

• We perceive objects as having a constant color, despite lighting, shading, etc.–A brick wall is still red, whether

bright sunlight is on it, or darkness has made it look gray.

Depth Cues

• Depth Cues allow us to perceive the world in three dimensions.– Monocular Cues are depth cues that do

not depend on having two eyes working in conjunction together

– Binocular Cues are depth cues that depend on having two eyes working in conjunction with each other

Monocular Cues

• Linear Perspective

• Relative Size

• Interposition

• Texture Gradient

• Shadowing

9. Linear Perspective

• Parallel lines seem to converge the further they get from us. The gradual reduction of image size as distance from the object increases

• Vanishing Point – where two parallel lines connect in the distance

10. Relative Size

• Objects on top of our horizon are smaller and further away, objects below are closer and larger

Elevation

11. Interposition

• Near objects partially obscure objects further away

12. Texture Gradient

• Patterns of distribution tend to grow more dense with distance – things further away seem more smooth, up close more detailed

13. Shadowing

•Lighted objects seem closer, darker further away

Binocular Cues

• Binocular Disparity/Retinal Disparity

• Convergence

• Motion Parallax

14. Binocular Disparity

• Each of our eyes sees an object from a slightly different angle, and the brain gets both images. The smaller the degree of the angle of difference, the closer the object is. The more disparity, the further the object is.

15. Convergence

• As objects get closer and further from us, our eyes move towards each other or away. The closer they are, the closer the object.

16. Motion Parallax

• Motion parallax is a function of the rate at which the image of an object moves across the retina. Distant objects will appear slow in comparison with close objects even when the two are moving at the same speed. Motion parallax can also be caused by the movement of the viewer's head. Objects closest to the observer will appear to move faster than those further away. This is an important cue to those who only have the use of one eye.