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Limits of Human Vision

  1. Sep 7, 2006 #1
    What is the lowest intensity of light that generates any stimulus in the human eye? In what wave length range?
  2. jcsd
  3. Sep 7, 2006 #2


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    The eye is most sensitive to green light, at approximately 515 nm. The actual sensitivity varies enormously from person to person, during the time of day, and with diet. It's difficult to pin down a single, specific number for the eye's sensitivity.

    - Warren
  4. Sep 7, 2006 #3


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    IIRC you can actualy see single photon events with the eye rod system.
    Can't get any lower than that.
    Not as images but simply as light flashes in the dark.
    Don't know the frequency range of the rod system.

    The eye cone system responds to 3 wavelenghts.
    Although I've heard that some people have two different color red receptors, which would make 4.
    The cone system requires a lot of light to operate.
  5. Sep 8, 2006 #4


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    Lowest intensity to obtain a stimulus may be measured in photons.

    One online reference describes, the minimum amount of light our brain requires to perceive light, is from 5 to 9 photons reaching the retina in a 100ms period.

    Another related concept is the dynamic range of our eye.
    see ref2. This is useful when viewing say; a deep space object through a telescope and you are trying to resolve this image. Your eyes need time to adapt to the darkness. The rods of your retina, are more sensitive to dim light than the cones.

    Across the whole visible spectrum, what wavelength are we most sensitive to? I found one reference (ref03) which is in agreement with Warren.
    Last edited: Sep 9, 2006
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