Color Vision Notes

Color Vision Notes

Three Dimensions of Color

  • Hue: The specific color perceived (e.g., "blue").
  • Saturation: The purity of the color; as white light mixes in, the color becomes less saturated (e.g., "electric blue" vs. "robin’s egg blue").
  • Brightness: The psychological intensity of a color (e.g., the difference between a dim blue spotlight and an intensely bright blue spotlight).

Color Mixing

  • Subtractive Mixing: Involves combining pigments with a single light source.
    • Example: Mixing paints.
  • Additive Mixing: Involves combining multiple light sources to create new colors.

Subtractive Mixing

  • Combining Pigments:
    • Red paint appears red because it reflects red wavelengths and absorbs others.
    • Each additional pigment absorbed more wavelengths, reducing light reflection.
  • Process: More pigments added mean more wavelengths absorbed and less reflected, resulting in the removal of light.

Subtractive Color Mixing Visualization

  • How it works:
    • Each pigment absorbs specific wavelengths and reflects others, leading to combined effects on color perception.

Additive Mixing

  • Combining Lights:
    • Each added light source increases the available wavelengths, enhancing brightness.
    • The resulting color can often be predicted using the color wheel.

Color Wheel Reference

  • Color Degrees:
    • Chartreuse (150°), Green (180°), Yellow (120°), Orange (60°), Red (0°), Magenta (330°), etc.

Metamers

  • Definition: Pairs of lights that appear identical but consist of different wavelengths.
    • Example: Yellow can be produced with a single wavelength or by mixing green and orange light in equal amounts.

Applications of Additive Color Mixing

  • Used in:
    • Color printing.
    • TVs and computer monitors.
    • Stage lighting.

Implications of Additive Color Mixing

  1. Three widely spaced wavelengths can create all visible colors.
    • Indicates efficiency of color production using limited receptors.
  2. Some colors do not mix (e.g., no true "reddish green").
    • Mixing can result in white light.
    • Related theory: Opponent-process theory suggests that certain color pairs are managed by the same underlying mechanisms.

Trichromacy Theory

  • Proposed by Young in the 1800s: Human beings have three types of color detectors in their eyes, enabling perception of the full color spectrum through additive mixing.

Combined Theories: Trichromatic and Opponent-Process

  • Cone Receptors: Respond to subsets of the visible spectrum.
  • Opponent Cells: Respond oppositely to pairs of colors such as blue-yellow and red-green, processing color information in a collaborative manner.

Determinants of Color Perception

  1. Wavelength: The specific wavelength dictates the color seen.
  2. Amount of Light: The intensity of the light affects brightness and visibility of color.
  3. Surrounding Colors: Impact of adjacent colors creating simultaneous color contrast.
  4. Recently Seen Colors: Influence perceptions of color based on previous visual experience (sequential color contrast).
  5. Memory for Typical Colors: Prior knowledge and memories impact how colors are perceived in context.