Colour part 1

Question 1

Why do we perceive colour? give examples

Answer 1

Signalling information about natural and human built environment (traffic lights, and bananas)
Perceptual organization of the world (where one object begins and the other one ends)
Object recognition (apple types)
Cultural transmission (used to represent ideas in society)
Aesthetics

Question 2

What are the two things we see for colour?

Answer 2

Wavelengths of light
Pure wavelengths (monochromatic light) –> laser –> narrow band of wavelength

Question 3

What is the region for visible light?

Answer 3

400-700 nm

Question 4

What are reflective curves?

Answer 4

Shows how much light is reflected off an object at different wavelengths?

Question 5

Is the light off an object just one wavelength?

Answer 5

No, lots of wavelengths

Question 6

What would the reflectance curve look like for lettuce and tomato?

Answer 6

Lettuce = more green reflected (MED wavelength)
Tomato = more red reflected (Long)
Still a distribution of wavelengths

Question 7

What would the reflectance curve look like for white paper?

Answer 7

lots of all colours reflected –> equal across spectrum

Question 8

What would the reflectance curve look like for gray paper?

Answer 8

equal but low reflectance

Question 9

What would the reflectance curve look like for black
paper?

Answer 9

Doesn’t reflect much

Question 10

What is extreme black called (0.2% reflectance)?

Answer 10

Vantablack S-VIS

Question 11

What are the primary colours?

Answer 11

Depends on what you are doing with colour
Just need 3 colours that are spaced along spectrum

Question 12

What are the colours used for printing?

Answer 12

Cyan, magenta, yellow

Question 13

What is reflection and subtractive colour mixing with paint?

Answer 13

Colour a paint looks depends on reflectance

Question 14

What wavelengths does yellow pain reflect?

Answer 14

Long and medium

Question 15

What wavelengths does blue pain reflect?

Answer 15

Small and medium

Question 16

What if you combine blue and yellow pain?

Answer 16

only reflects what yellow and blue both reflect = so medium

Question 17

What model does transmission and additive colour mixing use?

Answer 17

RGB colour model

Question 18

Is the RGB colour model opposite to CMY?

Answer 18

Yes

Question 19

What happens when all the colours in RGB are overlapped?

Answer 19

white

Question 20

What is transmission?

Answer 20

admitting light rather than absorbing like computer screens

Question 21

What model do LCD computer screens use and how do they work?

Answer 21

RGB
Each pixel has red, green, and blue piece = relative brightness determines what we see

Question 22

How to describe the full range of colours?

Answer 22

a 3 dimensional colour space

Question 23

How many colours can humans discriminate?

Answer 23

at least 2 million

Question 24

What are the three dimensions of the first colour space

Answer 24

Hue, saturation and value (HSV colour space)

Question 25

What is hue?

Answer 25

The chromatic or rainbow colour

Question 26

What is saturation?

Answer 26

The amount of white added (to the particular hue)

Question 27

What is value?

Answer 27

How light or dark the colour is

Question 28

What are 2 other versions of colour space?

Answer 28

HSL (hue, saturation, lightness), RGB (red, green, blue)

Question 29

What is hue, saturation and lightness in the HSL colour space?

Answer 29

Hue is the same, saturation is how grey, and lightness is how light

Question 30

Do you always need 3 dimensions for colour space?

Answer 30

yes

Question 31

How does red, green, blue colour space work?

Answer 31

For computer How much of each colour is turned on for each pixel ratio of each colour

Question 32

What could colours be?

Answer 32

Percepts Qualia Patterns of neural activity Properties of objects in the world

Question 33

What is qualia?

Answer 33

The "redness" of red unarticulable essence of colour

Question 34

What is the inverted spectrum argument?

Answer 34

How do I know my red is your red or maybe your red is like my green

Question 35

What is the trichromatic theory based on?

Answer 35

Colour perception is based on 3 principal colours Colour perception is based on 3 receptor types (cones) Colour perception is a 3 dimentional construct

Question 36

What is the experiment to support the trichromatic theory?

Answer 36

color matching experiments

Question 37

How does the the color matching experiments work?

Answer 37

Participants tries to match test field by adjusting the brightness of lights shining on comparison field Exactly 3 lights of different wavelengths are necessary to match all test field colours The participant can make it look identical to test field

Question 38

What colours does the colour matching experiment use?

Answer 38

RGB

Question 39

What are the three types of cones

Answer 39

Short (blue), medium (green) long (yellow)

Question 40

How do cones respond to colours of single wavelengths?

Answer 40

480 nm light causes activation of all 3 cones relative level of activation of each cone type gives colour information to brain

Question 41

What does white do to cone activation?

Answer 41

all three

Question 42

What are metamers?

Answer 42

two different stimuli that are perceptually identical Identical cone activation

Question 43

How do metamers work?

Answer 43

if you get a combo of the light that does the same activation of each cone type --> metamers Total activation of each type of cone is identical --> looks the same s= 0.2 + s= 0.8 = 1.0 total