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Tuesday, August 11, 2009

Light at Night

As most owls are active at night, their eyes must be very efficient at collecting and processing light. This starts with a large cornea (the transparent outer coating of the eye) and pupil (the opening at the centre of the eye). The pupil's size is controlled by the iris (the coloured membrane suspended between the cornea and lens). When the pupil is larger, more light passes through the lens and onto the large retina (light sensitive tissue on which the image is formed).The retina of an owl's eye has an abundance of light-sensitive, rod-shaped cells appropriately called "rod" cells. Although these cells are very sensitive to light and movement, they do not react well to colour. Cells that do react to colour are called "cone" cells (shaped like a cone), and an Owl's eye possesses few of these, so most Owls see in limited colour or in monochrome.Since Owls have extraordinary night vision, it is often thought that they are blind in strong light. This is not true, because their pupils have a wide range of adjustment, allowing the right amount of light to strike the retina. Some species of Owls can actually see better than humans in bright light. Humans, on the other hand have very poor night vision. I'm not saying we can't see at night just nowhere near as well as a lot of animals can. On the other hand humans have much larger brains than most animals, and we use our large brains to invent stuff. What kind of stuff you may ask. Well stuff like candles, lanterns, flashlights and night vision optics. Now I know that not everybody (myself included) can run out and drop $1600-$4500 on optics, but I really doubt that there is one person reading this that doesn't own a flashlight. I have an abundance of flashlights, lanterns and candles scattered through out my house. I also keep a flashlight in my truck, backpack and a small one on my keyring. If you are trying to move undetected at night make sure you have a colored lens (green or red are the most common). If you find yourself without a flashlight your cellphone will work in a pinch. Granted it's not much light but it will let you find an item you might have dropped or read a map or locate a flashlight. Now if you find yourself without anything to illuminate the night sky or dark room don't panic, as you all know humans can see at night, we just have to let our eyes adjust. The best way I have found is to close your eyes for about 30 seconds, then slowly open them. Your eyes should be fully adjusted to the night by then. Even with your eyes fully adjusted I still would not recommend taking a run through the woods. Leave that for the Owls.---MCK


Anonymous said...

Good post MCK. I have seen some pretty cheap night vision goggles, granted they probably aren't the best quality, but it would be a great item for a prepper to have.

Kentucky Preppers Network

Anonymous said...

In the army they taught us that your night vision increased for a longer time than 30 seconds--like 30 minutes or longer. Also, that red lenses did not destroy your night vision like white light does.


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