Humans and natural night vision?

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Offline ConfusedHermit

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Humans and natural night vision?
« on: 21/07/2012 23:44:21 »
If we had perfect natural night vision, would the idea of a dark environment or a tree’s shadow mean anything to us? Would nighttime just look like a less colorful daytime?

Another question would be 'What's different when we look through night vision goggles and what an animal with night vision AND can see a fair amount of color sees?'

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Offline evan_au

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Re: Humans and natural night vision?
« Reply #1 on: 22/07/2012 06:35:35 »
A sharp tree shadow requires a localised source of light, like the sun, moon or a streetlight. With good night vision, or a long camera exposure, you can see a darker area which is the shadow; with perfect night vision and no moon you should see a darker diffuse area under the tree where it shades the ground from most of the stars.

Humans perceive nighttime to be less colourful because the light-level is too low to operate the colour-sensitive cone cells in the human retina. All that is left is the rod cells, which are monochromatic, and more sensitive to the green-blue part of the spectrum.

However, a camera has red, green and blue sensors like our eyes, and if you leave the exposure long enough, you will pick up a full-colour image, even at night. What is missing is the light blue of the sky, since that is deflected sunlight (absent at night).

There are several types of night-vision goggles:
  • Some amplify starlight, and could produce a full-colour image from the range of colours in starlight. However, it is cheaper and higher resolution to just sense brightness monochrome. Displaying a colour image bright enough to be seen by the human eye would mean that the human eye is no longer dark-adapted.
  • Some goggles utilise infra-red radiation, which has no corresponding colours that the human eye can see. Again, it is possible to be sensitive to several bands of infra-red, but monochrome is easier to display.
Most animals with good night vision have lots of rods, and a tapetum lucidum; this is monochrome.
Animals like snakes can detect infra-red radiation, but this probably wouldn't create an image in the way we experience vision.
 

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Offline RD

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Offline ConfusedHermit

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Re: Humans and natural night vision?
« Reply #3 on: 22/07/2012 10:17:41 »
Thank you. I have more research to do :{D~