FM5-20 Camouflage, Basic Principles War Department, February 1944
FIGURE 18 1 -- Panchromatic film -- the most common kind used in aerial photography. The aerial photo interpreter gathers information from size, shape, shadow, and tone of objects.
18 2-- An infrared photograph of the same area shows up certain camouflage
areas. Artificial vegetation, for example, is revealed by this infrared