c. Types of Illumination. There are two types of illumination that assist engagement during low light or darkness: ambient light and artificial illumination. Both ambient light and artificial illumination can affect target perception (distance and size) and night vision capabilities.
(1) Ambient light is the light produced by natural means (i.e., the sun, moon, and stars). Considerable variations occur in ambient light due to the time of day, time of year, weather conditions, terrain, and vegetation.
(2) Artificial illumination is the light produced by a process other than natural means. There are two types of artificial illumination used in combat: air and ground. Artificial light can be used to illuminate an area for target detection or to illuminate a specific target to pinpoint its position.
d. Effects of Illumination. In some combat situations, ambient light and artificial illumination may assist a Marine in locating targets. However, this light can affect perception of the target and disrupt night vision. The introduction of artificial light requires the eyes to make a sudden, drastic adjustment to the amount of light received. This can cause a temporary blinding because night vision was abruptly interrupted. Ambient light also can cause a blinding effect; e.g., a Marine may experience temporary blindness or reduced night vision if a bright moon suddenly appears from behind the clouds.
(1) Light behind a Marine or light between the Marine and a target illuminates the front of the target and makes it appear closer than it is.
(2) Light beyond the target displays the target in silhouette and makes it appear farther away than it is. If the target is silhouetted, it is easier to see and easier to engage.
(3) Air illumination devices are in constant motion as they descend to the ground. This movement creates changing shadows on any illuminated target, causing a stationary target to appear as if it is moving.
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