132 lines
5.4 KiB
Plaintext
132 lines
5.4 KiB
Plaintext
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Nightvision
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a TêC production
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by Morpheus
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With help from FM-21-75
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You Can See at Night
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You can see much more in the dark than you realize. However, to take
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maximum advantage of this ability, you must understand how your eyes are
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constructed and how to use them to see best under conditions of poor
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visibility.
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Your Eyes Are Like a Camera
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Certain parts of your eyes compare to a simple camera.
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a. The lens focuses light entering the eye just as does the lens of a camera.
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b. The iris corresponds to the diaphragm of a camera, opening and closing to
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regulate the amount of light entering the pupil.
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c. The retina corresponds to the camera film. Light rays strike the retina,
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form an image, and cause an impression to be transmitted to the brain through
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the optic nerve. The brain tells us what we see. In a camera, the image is
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stored and fixed on film.
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Day and Night Eyes
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The cone area is composed of cone cells and rod cells, so-called because of
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their shapes.
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a. Cone cells enable you to see color, shape, and sharp contrast. A great
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deal of light is required to activate them and they are blind during periods
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of low illumination. For this reason, they are your day eyes. The cone cells
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are concentrated in the cone region, directly behind the lens, and decrease in
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number with distance from the center of the cone region.
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b. Rod cells produce a chemical substance called visual purple which makes
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them active in darkness or periods of low illumination. They are your night
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eyes. Rod vision enables you to distinguish black, white, and shades of grey
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and to distinguish general outlines. Most of the rod cells are in the area
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of the retina around the cone region. A few are in the cone region.
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Seeing at Night
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Using your eyes effectively at night requires the application of the
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principles of night vision - dark adaptation, off-center vision, and scanning.
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a. Dark Adaptation means allowing your eyes to become accustomed to low levels
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of illumination. It takes about 30 minutes for the rod cells to produce
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enough visual purple to enable you to distinguish objects in dim light. This
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may be accomplished by staying in a red-lighted area, or by wearing red
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goggles for 20 minutes, followed by 10 minutes in darkness (to allow pupils to
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open wide).
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b. Off-center vision is the technique of keeping your attention focused on an
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object without looking directly at it. When you look directly at an object,
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the image is focused on the cone region, which is not active at night. When
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you look slightly to the left, right, above, or below an object, the image is
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formed in the area of the retina containing rod cells, which are sensitive in
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the darkness. The most sensitive area in individuals varies, but usually is
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found by looking 6ø to 10ø away from an object. In effect, you look out of
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the corner of your eye.
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c. Scanning is using off-center vision to observe an area or an object. When
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you use rod vision, the visual purple in the rod cells bleaches or blacks out
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in 4 to 10 seconds, and the object observed disappears. As the visual purple
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in one area bleaches out, you must shift your eyes slightly so fresh rod cells
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are being used. Move your eyes in short, abrupt, irregular movements over and
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around your target, but do not look directly at it. Pause a few seconds at
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each point of observation because your eyes cannot see while in motion.
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Factors Affecting Night Vision
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Visual purple is chemically related to vitamin A, and a serious lack of
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vitamin A impairs your night vision. However, excessive amounts of vitamin A
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will not necessarily improve your night vision. Colds, headaches, fatigue,
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narcotics, heavy smoking, and excessive use of alcohol reduce your ability to
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see at night. Exposure to bright light for extended periods impairs both day
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and night vision.
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Preserving Night Vision
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Night vision is quickly destroyed if bright light is allowed to enter the
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eye. If this cannot be avoided, such as when you must enter a lighted area
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or observe in a temporarily lighted area, close and cover one eye to preserve
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the night vision in that eye. When the light goes away, the night vision
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retained in your protected eye enables you to see until the other eye becomes
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adapted to the darkness.
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Confidence
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Confidence is very important. You usually use your eyes where there is
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plenty of light, so you are used to sharp outlines and bright colors. In
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darkness, objects are faint, have no sharp outlines, and have little or no
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color. You must believe what your eyes tell you. Gain confidence by faithful
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practice in using the principles of night vision.
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Movement
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Usually you must move more quietly in the night than in the day. Here are
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some general rules to help you --
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a. Move around thick undergrowth, dense woods, and ravines. Your field of
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observation is reduced and it is difficult to move quietly.
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b. Move as quickly as circumstances allow, but avoid running if possible. You
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may fall or make unnecessary noise.
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Have Phun..
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To contact TêC (The Omega Company) for submissions/comments/etc,
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The Magna of Illusion
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201/579/6927 HST/V32bis
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NUP: Hypnos
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