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Aerial photographs were taken to demonstrate the conditions encountered by air search teams on sunny and cloudy days (with victims under cover and immobile), see figures 6, 7, 8. These photographs clearly illustrate how significant the difference is between these contrasting conditions. In fact, the photographer (who knew the location of the victim) experienced notable difficulty in spotting the subject on sunny days. He had no such difficulty on cloudy days. Victim in a prone position beneath a Palo Verde tree on a CLOUDY day. This unretouched photograph was taken from a normal search altitude. (Compare with Figure 7.) A larger Figure 6 (85 K) can be seen here.  Victim in a prone position beneath a Palo Verde tree on a SUNNY day. This unretouched photograph was taken from a normal search altitude. (Victim's position is pin pointed in Figure 8.) A larger Figure 7 (96 K) can be seen here.  It is evident that lighting conditions influence the effectiveness of air search teams. The harsh contrast of dark shadows with bright, reflecting open areas makes it difficult for scanners to adjust their vision for simultaneous searching in both lighting extremes. Also when the sun is low on the horizon shadows are longer and scanners commonly have to cope with looking into bright sunlight. These observations indicate that searchers may be most successful on overcast days with high levels of light but minimum contrast, or just before sunrise or just after sunset on bright, sunny days. As the level of light decreases to darkness search effectiveness will also decrease. Regardless of cloud cover it was exceptionally difficult to detect victims on the opposite side of bushy vegetation. This difficulty would presumably increase with distance from the aircraft. Immobile victims in the open were easier to detect than those under cover, and detectability increased dramatically with added motion. The scanners noted that sitting victims were generally more difficult to detect than those lying in a prone position. This may be because the sitting victim exposes less surface area to the scanner. It was found that scanners have difficulty in anticipating the relative size the victim will appear to be in the search area. Many scanners commented that at the onset of a search they were looking for something much smaller than the victim subsequently turned out to be. They stated that it would be helpful to provide a visual size reference at the beginning of a search mission to aid them.
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