Cover and Concealment

Light and Shadow

An opaque object absorbs light and creates a shadow. If the source of light is small object, the object absorbs all light striking it and creates a shadow of uniform density, such as a shadow created by a street light. If the source of light is larger, such as from windows in a room, the shadow varies in intensity, creating the umbra and penumbra. In the umbra, all rays of light are obscured so it is the darker of part of the shadow, while the penumbra is the lighter part. Thus, the penumbra is not entirely hidden from the observer. Someone trying to hide will stay in the deepest shadow, the umbra.

When eyes detect objects, they see movement first, then silhouette, and then color. To see in dim light after being in brighter light, the eyes must be given time to adapt to the low level of light. It takes about thirty minutes for the rod cells of the eyes to produce sufficient visual purple to enable the eyes to distinguish objects in dim light. When an object is looked at directly, the image is formed on the cone region of the eye, which is not sensitive to low levels of light. When the eyes look five to ten degrees above, below, right, or left of the object, the image falls on the rod cells, which are more sensitive to dim light. When looking at an object in dim light, the visual purple of the rod cells bleaches out in five to ten seconds and the image fades, so you must keep the eyes scanning so that fresh rod cells are constantly used. Move the eyes in short, irregular intervals over the object without looking directly at it, pausing a few seconds at each point of observation. In darkness, objects are faint, have no distinct outline, and have little or no color.

At night, keep your opponent in the light so he or she is looking from an area of light, which means his or her pupils have constricted. This means the opponent is looking into an area of darkness, where insufficient light exists to display an image on the cone region of the retina. When moving in shadows, select a path from one shadow to the next, crossing any exposed areas quickly and quietly. It you stand still in darkness in an unusual stance, such as a squat, the opponent will not recognize your silhouette as that of a human. Assume a posture which conforms to the shape of a shadow and remain within it.