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