JP 3-50 National Search and Rescue Manual Vol I - US Navy

645 Search Target
This effect can be minimized by not looking steadily at any
point of light and by having other objects in view. Another
common illusion occurs as an approaching or receding light
appears to expand or contract at a fixed distance. Shifting
gaze counteracts this phenomena.
A. The detectability of a target is related to target size, shape,
and distance from the observer, color contrast and brightness contrast
with the back ground, movement, and duration of exposure to the
observer.
1. Color helps in detection because it contrasts with the
surrounding or background colors. A small target that
contrasts with the background can often be seen more easily
than a larger target that blends with surroundings. However,
small targets can be seen only at limited distance regardless
of the color contrast. For the color to be effective, the eye
must look directly at the target because the color receptors
of the eye are concentrated in the center of the retina, and
objects that would be seen out of the corner of the eye are
unlikely to be detected by color contrast. White, yellow,
red, and orange colors provide good contrast against a water
back ground, but yellow and white objects are not easily seen
against whitecaps. Under whitecap conditions, red and orange
appear to be the easiest colors to detect.
2. Brightness will also influence a target's contrast with its
surroundings. For example, fluorescent colors (such as
international orange) are typically sighted at greater
distances than flat or dyed colors. The density of color in
fluorescent paint and tapes is so great that brightness
contrast combines with color contrast to improve target
detection probability by reflecting greater amounts of light.
3. In general, water wakes and colors are more
6-14