Color Vision #1

Question 1

The scientific study of color is considered to have started with

Answer 1

Newton. He experimented with prism.

Question 2

Retinal organization can be considered __ or __

Answer 2

Centripetal from photoreceptors to primary visual cortex or Lateral (horizontal and amacrine)

Question 3

Purkinje Shift

Answer 3

The change in peak sensitivity observed when

X: wavelength
Y: Relative excitation level

Question 4

What is the principle of univariance?

Answer 4

The absorption of a long wavelength quantum has the same effect on a receptor as the absorption of a short wavelength quantum.

One a quantum of light is absorbed, all info about wavelength is lost. Think about M and M example.

Question 5

The probability of absorption depends on

Answer 5

Wavelength and PR class (either S, M, or L)

Question 6

Wavelength is a ___ attribute, color is a ___ attribute.

Answer 6

Physical, perceptual

Question 7

Intensity is a _____ attribute, brightness is a ____ attribute

Answer 7

Physical, perceptual

Question 8

Object color is related to

Answer 8

The wavelength of light reflected from an object. Ex: a blue water bottle absorbs all colors, except blue. It reflects blue.

Question 9

color mixing addition

Answer 9

RGB and lights obey addition. When mixing light, you will most likely get white. When mixing RGB, you will get Cyan, Magenta, Yellow and white.

Question 10

Color mixing subtraction

Answer 10

CMYK and paints obey subtraction. When mixing paint, you will get the result of the two colors you had in common. Ex: mixing yellow (red and green) with magenta (blue and red), you will get red (which is what the two colors have in common).

Question 11

Metamers

Answer 11

Two or more stimuli that have the same color but have different wavelength compositions. Color will change based on the light source landing on it.

Question 12

Metamer properties (3)

Answer 12

Scalar: If you increase intensity of both metamers, they will still be metamers.

Addition: If you add the same wavelength to both metamers, they will still be metamers.

Associative: If a 3rd meatier is created for 1 metamer, all 3 will be metamers.

Question 13

Spectral color vs non spectral color

Answer 13

Spectral: Obtained directly by prismatic decomposition of sunlight.
Non spectral: Not present in sunlight. Can be obtained only by mixing spectral colors. Some purples.

Question 14

Color circles, triangles, and cubes provide ___ description of color matches

Answer 14

Qualitative

Shows that 2 colors may not be sufficient to make color matches. May need to change saturation. May use to use negative colors- take some color away and move to other side of bipartite field.

Question 15

Complementary colors

Answer 15

any 2 colors that when added together, produce a neutral color (black, grey, white). On opposite sides of white in color triangle/circle/cube.

Red: Cyan (KU)
Green: Magenta
Blue: Yellow (KU)

Question 16

Munsell term for hue

Answer 16

Wavelength

Question 17

Munsell term for saturation

Answer 17

Chroma

Question 18

Munsell term for brightness

Answer 18

Value

Question 19

On a cylinder, where would hue, saturation, and brightness be?

Answer 19

Hue: around the rim
Brightness: Vertical axis. White at top. Black at bottom.
Saturation: Center to periphery. Center is desaturated. Periphery is saturated.

Question 20

Color purity

Answer 20

The physical correlate of saturation, which is perceptual. Describes the proportion of pure, dominant spectral wavelength energy relative to the amount of achromatic light.

Color purity= wavelength you are interested in/ (wavelength you are interested + White wavelength)

Question 21

Values for color purity
0
1
and 0-1

Answer 21

0= completely white/achromatic 
1= completely pure. No achromatic light 
0-1= contains some white/achromatic light.

Question 22

Color mixing. For each wavelength matched, there is a set of 3 proportional values (primary colors) that add up to ___. This specifies the proportion of each primary color. These values are referred to as tri-stimulus values.

Answer 22

1.0

Question 23

Tristimulus values plotted against spectral wavelength results in a graph that looks like

Answer 23

Red dips into a negative zone. Must be put on other side of bipartite circle. In order to bypass this, imaginary colors were created

Question 24

What are imaginary primaries and why were they created?

Answer 24

imaginary primaries were created to get rid of the negative red value from the tristimulus graph.
However, values go outside of the value one.

Question 25

Tri stimulus values add up to ___

Imaginary colors add up to ___

Answer 25

1

Greater than one. Equation to convert back to 1.0

Question 26

How to get imaginary primaries to equal 0

Answer 26

Imaginary primaries are all uppercase.

x= X/X+Y+Z 
y= Y/X+Y+Z
z= Z/X+Y+Z

X/x= Y/y= Z/z

Question 27

What is the CIE (chromaticity diagram) used for?

Answer 27

Is a tool for specifying how the human eye will experience light with a given spectrum. It cannot specify color of objects because the color perceived when looking at an object is also dependent on light source.

Question 28

Where are these located at on a CIE diagram?

1. Spectral locus
2. Planckian locus
3. Non spectral purples
4. White

Answer 28

1. Around the edges. Where spectral colors are located from sun.
2. In the center of field. Blackbody radiator. Shows how change in temp will change the color.
3. At flat part on bottom. Colors we perceive, but not spectral. Not from the sun.
4. The very center

Question 29

How to find these on a CIE diagram?

1. Dominant wavelength
2. Complementary wavelength

Answer 29

1. Draw a line from white to the color to the spectral wavelength locus. That is the dominant wavelength.
2. Draw a line from the dominant wavelength, through white, and to another spectral wavelength locus on the other side of white.

Question 30

Excitation purity is the same thing as

Answer 30

Colormetric purity.

Excitation purity: a/a+b
1= pure
0=white

Question 31

Color gamut

Answer 31

Set of all colors that can be obtained from all possible mixtures of a specified set of primary colors. Ex: HDTV gamut is a subset of the entire CIE diagram. Not as good as human color vision.

Question 32

MacAdam Ellipses

Answer 32

JND for chromaticity (saturation) for a person with normal color vision.

Can be seen on a CIE diagram. Start at 1 location, how far can I move in a direction before someone can tell the color changes.

Ideal for the JND’s (perceived chromaticity) to be equal across the graph.

Question 33

Saturation/chroma is ___, colorimetric purity is ___

Answer 33

Perceptual

Physical