Course 2.4 Perception
Problem 4: Color
Literature: Goldstein
Basics of color:
- Function of color: signaling, perceptual organization, enhance contrast in the environment
(otherwise objects appear similar), recognition of objects
- Colors we perceive:
o Description of all colors possible with red, green, yellow, blue (→ basic colors)
o Color spectrum with colors between basic colors = extraspectral colors (mixture of basic colors)
o Humans can distinguish between 200 different colors + create millions more by adding white
(→saturation)
o Only really need a few on day-to-day basis (some color book show about 1200 colors
- Colors and Wavelengths
o Perception of color linked to physical property of wavelength
o Visible for humans 400nm – 700nm
400-450nm violet 500-575nm green 590-620nm orange
450-490nm blue 575-590nm yellow 620-700nm red
o Reflectance = determines color of object.
Reflectance curve = percentage of reflected light vs. wavelength
o Achromatic colors: black/white/gray reflect all wavelengths equally across spectrum
o Chromatic colors/hues: reflect some wavelengths more than others (→selec ve reflec on)
o Transparent objects: letting some wavelengths pass through (→selec ve transmission)
- Wavelengths don’t have color!
o Color is not in the waves, but created by perceptual system (→property of the brain)
o Arbitrary connection between wavelength and “color”)
o Waves are same for living organisms, but different species perceive different colors (→ NS
processes information differently)
Theory 1: Trichromatic Theory of color vision. Young-Helmholz Theory
= color vision depends on three different receptor mechanisms
- Evidence for theory:
o Color-matching experiment: adjust 3 wavelengths to match the 1 wavelength color in the
comparison field
o Findings:
1. Adjusting 3 wavelengths → possible to match any wavelength in the test field
Problem 4: Color
Literature: Goldstein
Basics of color:
- Function of color: signaling, perceptual organization, enhance contrast in the environment
(otherwise objects appear similar), recognition of objects
- Colors we perceive:
o Description of all colors possible with red, green, yellow, blue (→ basic colors)
o Color spectrum with colors between basic colors = extraspectral colors (mixture of basic colors)
o Humans can distinguish between 200 different colors + create millions more by adding white
(→saturation)
o Only really need a few on day-to-day basis (some color book show about 1200 colors
- Colors and Wavelengths
o Perception of color linked to physical property of wavelength
o Visible for humans 400nm – 700nm
400-450nm violet 500-575nm green 590-620nm orange
450-490nm blue 575-590nm yellow 620-700nm red
o Reflectance = determines color of object.
Reflectance curve = percentage of reflected light vs. wavelength
o Achromatic colors: black/white/gray reflect all wavelengths equally across spectrum
o Chromatic colors/hues: reflect some wavelengths more than others (→selec ve reflec on)
o Transparent objects: letting some wavelengths pass through (→selec ve transmission)
- Wavelengths don’t have color!
o Color is not in the waves, but created by perceptual system (→property of the brain)
o Arbitrary connection between wavelength and “color”)
o Waves are same for living organisms, but different species perceive different colors (→ NS
processes information differently)
Theory 1: Trichromatic Theory of color vision. Young-Helmholz Theory
= color vision depends on three different receptor mechanisms
- Evidence for theory:
o Color-matching experiment: adjust 3 wavelengths to match the 1 wavelength color in the
comparison field
o Findings:
1. Adjusting 3 wavelengths → possible to match any wavelength in the test field
