• The eye– curved

cornea– lens– retina– fovea– optic disk

Using Light

• photoreceptors transduce incoming light• ganglion cells send signals along to the brain

The Retina has layers of cells

• 2 types of photoreceptors: rods and cones

• rods are very sensitive - useful in dim light

•

Two kinds of Photoreceptors

• Rods and cones are distributed differently across the retina

The Retina

• visual acuity (ability to see detail) depends on cones - thus acuity varies across the visual field

The Retina

• Why don’t you notice your blind spot?

The Retina

• Why don’t you notice your blind spot?– Blindspots don’t overlap!– Your brain “fills in” the missing information– The specific information in the blindspot isn’t much

more missing than the rest of the periphery!

The Retina

• three types of cones: short, medium, and long• different absorptions enable color vision

The Retina

• Ganglion cells project to the brain via the optic nerve

• information is projected to contralateral cortex!

Visual Pathways

Seeing Depth

• What’s the big problem with seeing depth ?

Seeing Depth

• The world is 3D, the retina is 2D !

Depth Cues

• Four categories:1.Pictorial2.Physiological3.Motion4.Stereoscopic

Depth Cues

Pictorial Depth Cues: aspects of 2D images that imply depth

Depth Cues

Pictorial Depth Cues: aspects of 2D images that imply depth Physiological Depth Cues: Proprioception in ocular muscles indicates accommodation

and convergence

Depth Cues

Pictorial Depth Cues: aspects of 2D images that imply depth Physiological Depth Cues: Proprioception in ocular muscles indicates accommodation

and convergence Motion Depth Cues: foreground and background move in opposite directions

Depth Cues

Pictorial Depth Cues: aspects of 2D images that imply depth Physiological Depth Cues: Proprioception in ocular muscles indicates accommodation

and convergence Motion Depth Cues: foreground and background move in opposite directions Stereoscopic Depth Cues: disparity between two retinal images indicates distance

Pictorial Depth Cues

– Occlusion

Pictorial Depth Cues

– Occlusion

Pictorial Depth Cues

– Shadows and Shading

Pictorial Depth Cues

– Shadows and Shading

Pictorial Depth Cues

– Shadows and Shading: visual system assumes light from above

Pictorial Depth Cues

– Shadows and Shading: visual system assumes light from above

Pictorial Depth Cues

– Shadows and Shading