CS1020:   Introduction to Computers
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Human Visual System

Light is measured by frequency:

Ultraviolet <---- Visible Spectrum (350-780 nanoseconds) ----> InfraRed

Light Source: Characterized by the amount of energy it emits at every wavelength.

The spectrum of a light source shows is the distribution of light energy vs. wavelength (lambda).

Perception of Light:

  1. Brightness. Brightness= the amplitude of the spectrum.
  2. Hue. Informally refered to as color.
    1. frequency componets of spectrum
    2. characterized by dominant frequency
    3. wavelength DOES NOT equal hue.
  3. Saturation. Spectral width, describes "whiteness" of a color
    1. unsaturated = a lot of white
    2. saturated = no white
Color Circles
  1. Emitted Light
The light from a monitor or projector. The primary hues are green, red, and blue. "Combining" any two opposite colors = white.
  1. Reflected Light
Primary hues are yellow, cyan, and magenta. "Combining" opposites = black.

The Human Eye

Three levels of membranes.

Outer = Cornea: Transparent area, and Sclera: Opaque

Choroid:

  • network of blood vessels
  • heavily pigmented
  • ciliary muscle: allows focusiing of the lens
  • iris: like a diapragm, controls quantity of light
Lens:
  • made of layers of tissue
  • 60 -70% water
  • slightly yellow
  • absorbs 8% of visible light
Retina:
  • contains photorecptors, sensors that detect light
  • contains rods and cones
Fovea: Part of retina w/ central vision. Most cones are located here, w/ less rods.
  • rods:
    1. 120 million, several per nerve ending
    2. achromatic vision = b/w, grayscale
    3. work well in low light conditions
    4. low spatial detail
    5. related to peripheral vision
  • cones
    1. 6-7 million
    2. fovea
    3. color
    4. fine detail
    5. work well in bright light
    6. 3 types, r, g, b
  • Our perception to brightness
© Lynne Grewe