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See also: Color, Color Questions




Rods much more numerous than cones, responsible for vision in dim light, out of commission in bright light

Cones do not respond to dim light, are responsible for fine detail and color perception  (Eye, Brain and Vision p36)


Measuring the rate on impulse of an on-center retinal ganglion cell, it pulses with no stimulation, and as an illuminated dot in its receptive field grows, it pulses more often, then starts to decline as the dot grows to a size invading the antagonistic surround.  The receptive fields of ganglion cells adjacent to it almost completely overlap. (EBV p42-3)



A human can see a flash of light so feeble that no single receptor can have received more than a single photon of light.  (About six closely spaced rods must be stimulated within a short time to produce a visible flash.)  (EBV p49)


Other Animals


  • Mantis Shrimp (wikipedia) have 16 different cones, twice as many as any other known animal


Human Development

  • A study of historical use of color terms across human cultures found that all societies studied discovered:
    • 1. black and white
    • 2. red
    • 3. yellow
    • 4. green
    • Last: blue






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