Chapter 5 (colour)

Question 0

White paper

Answer 0

High reflectance, light bounces back

Question 1

What is lightness reflects cd?

Illusions

Answer 1

Actual reflectance of surfaces in world, perception of light reflected on each surface regardless of light variations

Question 2

Chocolate bar

Answer 2

Low reflectance, light is absorbed

Question 3

Color consistency

Answer 3

Is achieved when visual system choices lightness consistency by applying assumptions about the way light sources and surfaces interact in the world, thus the illusion is perceived

Question 4

What is color consistency?

Answer 4

Disconnecting effects of lighting conditions to determine true color of object

Question 5

After images

Answer 5

Result from operation of of opponent process in visual system

Question 6

3 types of output for after images

Answer 6

1. Red green
2. Blue yellow
3. Black white

Question 7

Mechanisms of after images

Answer 7

Visual system contains some cells that get excited by red light and inhibited by green light and visa versa

Question 8

Results of after images

Answer 8

Eye is still firing colors even when color disappears

Some R- +G cells firing faster than R + G- cells hence why not seeing the plain white square

Question 9

What causes color blindness?

Answer 9

Congenital absence of 1 come ( usually L or M cone in males)

Question 10

Cone types

Answer 10

L come- long wavelength
M come- medium wavelength
S cone- short wavelength

Question 11

Mechanisms of color blindness

Answer 11

Not blind to differences in wave length but color perception is based off outputs of 2 cones instead of 3

Question 12

Folded card illusion

Answer 12

Visual system assumes changes in luminance are due to lighting shifts caused by folds in card not changed in surface reflection

Question 13

Lab example of folded card illusion

Answer 13

Folded card looks as if light source is coming from above

Question 14

Bumps and dimples

Answer 14

Visuals system makes 2 assumptions:

• portion of surface that faces towards light source will be brighter than portion away from light
• assume light source is coming from above

Question 15

Checkerboard shadow illusion

Answer 15

Visual system is not able to disregard interpretation of light sources in scenes when making judgements about the brightness of surface

Question 16

Color perception definition

Answer 16

Color is our subjective wavelength that perception ends up bouncing off the object and into our retina

Question 17

How is color perception transferred in eye?

Answer 17

1. Photoreceptors start process by selectively responding to different wave lengths
2. 3 different cone receptors used for the color (trichromacy)
3. Then 3 comes translate into opponent process mechanisms (like red vs green of blue vs yellow) which is responsible for after images

Question 18

What is the purpose of the visual system?

Answer 18

• to tell us what is out there rather than the wavelengths
• take into account the luminance characteristics of a scene to tell us the actual colors in the world ( color constancy)