Night Vision - How the Eyes See at Night Fisher Swale Nicholson

Night Vision, is it a trick of the eye?

This Halloween season you may find yourself lying in bed with the lights off when out of the corner of your eye you see a hazy outline. You quickly turn on the lights only to realize there is nothing there but a dresser. Did you see a ghost? 

Human vision is not as strong at night as it is in a light environment, that’s just a fact of our human anatomy. Although we may be able to distinguish ambiguous shapes and outlines, our eyes do not have the same capabilities of animals with perfect night vision. Unless you live in a haunted house, the reason for the hazy outline was your eye catching some light from your bedroom window or other source of light like the edges of a closed door.

The Simple Mechanics of Night Vision

To understand night vision, you need to understand a little of the mechanics of how we eyes see. The three parts of your eyes that help you see are:

  1. Pupils: Your pupils expand to let light in and retract to block light out.
  2. Cones: Your cones help your eyes recognize color and detail in bright lights.
  3. Rods: Your rods help your eyes recognize black, white and grey shades, as well as shapes in dim lights.

It takes your eyes about thirty minutes to adapt and adjust to darkness. Things that can affect our ability to adapt to seeing at night are:

  • lack of vitamin A
  • colds, headache, fatigue
  • narcotics, alcohol and tobacco use
  • prolonged exposure to bright light
  • physical conditions

Nocturnal Animals

Animals like owls and cats have perfect night vision because they have more rods than we do. Take cats for instance; according to Tia Ghose writer for Live Science, cats have six to eight more rod cells than humans allowing them to see clearer pictures in the dark and making them perfect companions to warn us if something uninvited is hanging around your house.

Night Vision Technology

What if you don’t own an animal with night vision? You’ll need additional technology to help you see those spooky apparitions. Fortunately engineers have created two types of night vision goggles to make ghost hunting possible.

Image enhancement: Image enhancement collects all the available light and intensifies it through two green lenses in the goggles. Human eyes can process green light better than other colored light.

Thermal imaging: Thermal imaging detects infrared light produced by heat in objects; it looks a lot like weather radar. The more intense (hotter) the temperature, the more red the object will appear. You’d have better chances locating a ghost with thermal imaging. Ghosts lack body heat and would show up blue in the goggles.

Don’t be discouraged that your eyes aren’t made for perceiving depth and motion at night. The fun of Halloween are the tricks that get played on our eyes.

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