Combat targets are frequently engaged during periods of darkness or under low-light conditions. Basic marksmanship fundamentals do not change, however, the principles of night vision must be applied and target detection is applied differently. During periods of darkness or low light, a Marine's vision is extremely limited. A Marine must apply the techniques of night observation in order to detect potential targets, and he must develop skills that allow him to engage targets under these conditions.
a. Night Vision. A Marine can improve his ability to see during periods of darkness or low light by obtaining and maintaining night vision. Since adapting to night vision is a slow and gradual process, steps should be taken to protect night vision once it is obtained.
(1) Obtaining Night Vision. There are two methods used to obtain night vision. The first method is to remain in an area of darkness for about 30 minutes. This area can be indoors or outdoors. The major disadvantage of this approach is that an individual is not able to perform any tasks while acquiring night vision in total darkness. The second method is to remain in a darkened area under low intensity red light (similar to the light used in a photographer's darkroom) for about 20 minutes, followed by about 10 minutes in darkness without the red light. This method produces almost complete night vision adaptation while permitting the performance of some tasks during the adjustment period.
(2) Maintaining Night Vision. Because the eyes take a long time to adjust to darkness, it is important to protect night vision once it is acquired. To maintain night vision:
• Avoid looking at any bright light. Bright light will reactivate the cones in the eye and deactivate the rods, eliminating night vision and requiring readaptation.
• Shield the eyes from parachute flares, spotlights, or headlights.
• When using a flashlight to read a map or other material:
• Put one hand over the glass to limit the area illuminated and the intensity of the light. Keeping one eye shut will reduce the amount of night vision lost.
• Cover the light with a red filter to help reduce the loss of night vision.
• Minimize the time spent using a flashlight.
(3) Factors Affecting Night Vision. Some physical factors may affect your night vision and reduce your ability to see as clearly as possible in low light or darkness. These factors include:
• Long exposure to sunlight.
• Consumption of alcohol within the past 48 hours.
b. Searching Methods. Once night vision has been acquired, the Marine can located targets. Some daylight observation techniques (e.g., searching for target indicators) also apply during periods of darkness or low light.
(1) Off-center Vision. Off-center vision is the technique of keeping the attention focused on an object without looking directly at it (see figure 10-13). To search for targets using off-center vision, never look directly at the object you are observing. You will see the object much better by using off-center vision. Look slightly to the left, right, above, or below the object. Experiment and practice to find the best off-center angle for you. For most people, it is about 6 to 10 degrees away from the object, or about a fist's width at arm's length.
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