Camouflage

CAMOUFLAGE, el' moo-flazh. This art is in reality an adaptation of the science of color to meet man's requirements according to the plan of nature's protective coloring but the idea may be greatly extended in scope as will be briefly suggested in the following paragraphs. It is well known that many species of birds, fishes and animals assume colorings and patterns which quite effectively conceal them in their natural environments. Some of these change their colorings and patterns from season to season and the chameleon and cer tain fishes have the ability to alter their color very quickly to an approximation of that of their immediate surroundings. Some fishes are also able very quickly to imitate approximately the pattern of the background upon which they are placed. The effectiveness of this scheme of protective coloring has indicated to man the possibility of providing protective concealment for men, batteries, etc., in warfare and in other activities and the science of color has revealed other possibilities. In utilizing this art in war fare the aim is to provide a covering which closely imitates that of the surroundings. In order to provide effective concealment it is necessary to consider the character of the lighting and herein the greatest obstacles are usually encountered because of its cbangeable ness. The scheme will be introduced by means of a few examples. It is easy to mask a battery in the summer time amid green foliage by using a screen of green branches, grass, etc. The duck-hunter utilizes a suit of grass or a blind of vegetation in the same manner. In other seasons suitable changes in the screens may be made. If soldiers are to be concealed in a snow-covered winter landscape which is devoid of vegetation this may be accomplished by means of white clothing and even white masks or paint on their faces. On an overcast day the concealment may be accomplished quite effectively but on clear sunlit days the shadows cast upon the surface of the snow and the shadows on the various contours of the form i usually render complete deception impossible especially if the soldiers are moving. If the winter landscape is not wholly barren of trees or shrubs and the soldier is on stationary out post duty, a dark gray cloak is effective. In the case of vessels it has been found that a mottled pattern of grays has been quite effec tive toward rendering them less conspicuous or practically invisible. If the vessels lie low in the water it is obvious that the deception is generally more successful. However, the ap pearance of the surface of the water varies with the lighting and with the character of the sky and of the waves. It is obvious that the surface of the water assumes many appearances with a given lighting and sky condition, in cluding the calm smooth surface, the choppy sea and the long swells or rolling sea. To a distant observer these differ least in appearance on a uniformly overcast day. On a sunlit day there are usually bright high-lights on the waves which are reflected images of the sun. Furthermore the surface color of the water is largely due to reflected images of the sky and clouds. The color of a smooth surface of the water at some distance from a given observer appears to him quite similar to that of the lower portion of the sky in the direction in which he is gazing. This is readily seen if a diagram is made and the optical law of reflec tion— the angle of incidence is equal to the angle of reflection — is applied. When small waves are running, beautiful color-effects are seen if the color of the zenith or upper por tions of the sky differs materially from that of the lower sky near the horizon, as is usually the case after sunset. Such a surface of water appears to be a series of stripes alternating in color. From the simple diagram previously suggested it will be seen that the lagging side of a wave is reflecting toward the observer an image of a patch of sky near the horizon and the advancing side is reflecting an image of a patch somewhat nearer the zenith. If these patches are different in color, the beautiful effects already mentioned are accounted for. These different appearances of the water have been discussed in order to show that the best protective coloring for vessels differs according to lighting, sky condition, and surface char acter of the water. In other words, if prac ticable, several removable coatings, differing in pattern, could be provided. In general the most suitable color is bluish gray but there is always the difficulty with glint or high-lights, even if smoke can be suppressed or avoided. It is a comparatively simple problem to provide a coat ing for rendering a low-lying ship incon spicuous or even invisible under specific con ditions of lighting, sky and surface of the water ; however, in practice a compromise must be made in order that one coating will serve well under all conditions. In marine camouflage the outline of the vessel is important for it is usually seen against the sky by the sub marine or distant enemy. The science of color can be used effectively in revealing guns, soldiers, etc., belonging to the enemy if they have not been provided with coverings closely resembling their environments. The plan is quite the reverse of camouflage in that it aims to augment the contrast in hue or in brightness. In general, all objects are °colored)); that is, relatively few objects are without hue. The latter are the whites, blacks and intermediate grays. We see an object only when there is a contrast between it and its background or im mediate surroundings. This contrast may be in hue or in brightness but usually it is a mixture of both. Camouflage aims to eliminate

these contrasts. It is a fact of color-science that a colored object — for example, a pigment — will not appear, in general, the same under two different illuminants. Both the hue and value or reflection factor of a colored object change with the illuminants. For example, in Fig. 1 are shown the relative values or bright ness-contrasts of six colored fabrics under red, green and blue lights, respectively, as indicated. For example, the lower middle one, which was a blue fabric, is very dark under red light and is very bright under blue light. This experi ment is significant in indicating the possibilities of using various colored screens before the eyepieces of field glasses and telescopes. A study of a landscape by means of such filters may reveal objects owing to the augmented contrast which would not be otherwise suffi ciently conspicuous. Experiments made by the author before the beginning of the European War indicated such possibilities. For example, a khaki cloth amid green foliage may be made to appear darker or brighter than the sur rounding green foliage by viewing it through blue-green and yellow-orange filters respec tively. Actual measurements of the ratio of the brightness of the khaki cloth to that of a green leaf were respectively 0.7 through a blue-green filter, and 1.5 through a yellow-orange filter. These ratios are on the basis that, tinder day light illumination, the two objects appeared of the same brightness when viewed without colored filters. The applications of colored screens to field glasses appears to be well worth while for many purposes outside of warfare. In order to meet all the conditions to be found, a series of filters, say blue, green, yellow, orange and red, could be provided in pairs for field glasses and arranged in a convenient man ner for quickly changing from one set to another. These screens should be as pure in color as practicable. Another promising filter is a yellow or canary screen whose object would be to eliminate the bluish hate which is usually present in distant landscapes. A large per centage of light is sacrificed with such screens but fortunately the intensity of daylight is usually far greater than is necessary. It is doubtful that artificial light will play an ap preciable part in the art of camouflage in war fare; however, it has possibilities in other fields in certain developments in color-effects ap plicable to the stage, etc. Applying the ciple already discussed briefly in connection with Fig. 1 it is possible to relate various colors with certain patterns in such a manner that certain parts of the scene will disappear completely under a given illuminant. For ex ample, a gray on a red background is readily distinguished under ordinary light because of the difference in brightness and in hue. Under a red light there will be no difference in hue if the red background has been properly selected in relation to the illuminant. There remains, then only the possibility of a con trast in brightness which depends upon the relative amounts of light reflected by the gray and red objects. If the gray is properly selected it will appear of the same brightness as the red background under the red light and therefore will be indistinguishable or invisible. By the use of the same principles applied to a number of pigments (those having the quality of high transparency being more satisfactory), striking disappearing effects can be obtained by varying the color of the illuminant. The effect which is possible by applying these principles is illustrated in Fig. 2 although rather feebly, owing to the absence of color, The paints which were made of high transparency and purity were so chosen . that under ordinary illumination the scene appeared as in the illus tration at the left. Under an orange-red light the mountain and entire background disap peared with the result that the scene appeared as in the right-hand illustration.

This example indicates what could be ac complished outdoors if both the landscape and lighting could be controlled. Many effects have been produced on canvas, such as changing a summer landscape to a winter scene, causing figures to disappear, etc. The scheme has possibilities on the stage, in displays and in advertising. Ordinary pigments are not as satisfactory as water colors or paints made by coloring a white base with aniline dyes. In applying the art of camouflage it is seen that the science of light and color contains the under lying principles. With a thorough acquaintance with these much can be accomplished. Even some of the efforts of the enemy to conceal soldiers, batteries, etc., could be rendered in effective by utilizing colored screens on tele scopes and field glasses unless the colors were very carefully chosen by the enemy. For ex ample, for perfect concealment the object must possess the same color as its surroundings, not only as viewed by the eye but as analyzed by the spectroscope. This point is too intricate to discuss in detail but in color-work it is always well to remember that in respect to color the eye is synthetical and not analytical. In other words, the eye records only the integral effect of the spectral colors of which ordinary colors consist. For example, two yellows may appear the same to the eye under a given illuminant though they may be quite unlike in spectral composition. If the latter is true, the two yellows will not in general appear alike under any other illuminant. Camouflage has been practised in all wars, but in the European War it has been highly developed. Consult Luckiesh, M., 'Color and Its Applications.'