Color Properties - Brightness & Chromaticity

Question 1

Describe brightness

(What two channels contribute to brightness, is it additive, what is the physical mesaurement of brightness, what the max scotopic and photopic wavelength?)

Answer 1

• Made up by chromatic and luminance channels
• Brightness not additive
• Measured by luminance
• Photopic max is 550 nm, Scotopic max is 500 nm

Question 2

Describe the luminance function

(What shape does it look like, what is the max wavelength for Normal trichromat, what variations in the function for Deutan and Protan)

Answer 2

• Bell shaped curve
• Normal trichromat max 555 nm
• Deutan slightly different for longer wavelengths
• Protans slightly different towards shorter wavelengths

Question 3

Which is NOT a phychological factors in Chromaticity discrimination?

A. Hue
B. Saturation
C. Brightness
D. Chromaticness

Answer 3

C. Brightness

Question 4

How is the Munsell color system applied towards color vision testing?

(How is it used?)

Answer 4

• Used for specifycolor paper for color vision testing

Question 5

What are the three factors that the Munsell Color System look at?

(What catagories does wavelength, saturation, colormetric purity, lightness/darkness fall under?)

Answer 5

1) Hue (wavelength)
2) Chroma Scale (Saturation/Colormetric Purity)
3) Value (Lightness/Darkness)

Question 6

Define color constancy and list two exceptions to it.

(What happens to color with changes in illumination?)

Answer 6

• Most colors remain constant despite changes in illumination
• Benzold-Brucke effect and Abney effect are exceptions to this

Question 7

Can luminance change hue for monochromatic stimuli?

• What color appears if you increase luminance for longer wavelengths (>503 nm, Red Green)?
• What color appears if you increase luminance for shorter wavelengths (

Answer 7

• YES
• Increased luminance for red-green wavelengths appears more yellow
• Increased luminance for blue-green/violet wavelengths appear more blue

Question 8

What are three specific wavelengths that do not change with increased luminance? Why is that? (related to opponent color theory)

Answer 8

• 478, 503, 578 nm

- Due to balance between R-G and B-Y opponent channel

Question 9

Which is NOT an invariant wavelength?

A. 478 nm
B. 503 nm
C. 555 nm
D. 578 nm

Answer 9

C. 555 nm

Question 10

Describe the Abney effect and give two exceptions

Relates to chromatic purity and hue

Answer 10

• Hue changes as you add white

- Exceptions are Yellow and non-spectral bluish-purple

Question 11

What is the Benzold-Brucke effect?

(What does luminance due to hue?, What happens to R-G, B-Y, Are there unique wavelengths that do not change hue with increased luminance?)

Answer 11

• Luminance can change hue for most monochromatic stimuli
• increased luminance for R-G looks yellowish
• increased luminance for B-Y looks blue
• There are three unique wavelengths that do not change hues with increased luminance