THE PHOTOGRAPHIC EYE
Although camoufleurs made perfect imitations of natural objects and surroundings, they were greatly concerned to find that the flying observers could see through their disguises. To the naked eye the landscape would not show the slightest trace of any suspicions object, but by the use of a color-screen to cut out certain rays of light, a big difference would be shown between the real colors of nature and the artist's copies of them. For instance, if a roof painted to look like green grass were viewed through a red color-screen, it would look brown; while the real grass, which apparently was of exactly the same shade as the roof, would look red. It had not been realized by the artists who had never studied the composition of light, that there is a great deal of red in the green light reflected by grass, and that if they were to duplicate this shade of green, they must put a certain amount of red paint in their imitation grass roofs. Air scouts did not depend upon their eyes alone, but used cameras so that they could study their photographs at their leisure and by fitting the cameras with different color-screens, they could analyze the camouflage and undo the patient work of the artist.