Principles of Concealing coloration of military aircraft – Chapter One, Part 1

Prolog

I have an interest for concealing coloration and camouflage since I built all those planes and tanks with stripes and mottlings in my childhood. I have a special interest in German WWII aircraft, as well as in ships, tanks and art that uses and plays with the principles of concealing and camouflage.
Over the years I did notice that all books that I have on camouflage, especially on military aircrafts, are of a descriptive and narrative nature on all the various colors, paints, schemes and markings. But none of these books explain any principles on how and why a camouflage works – or didn´t work.
A further impetus to think about the mechanisms of concealing and camouflage of military aircrafts was a conversation with Jürgen Kiroff, a chemist and maker of historic lacquers and paints, on why some Luftwaffe colors were newly introduced, others replaced and some maintained over the course of the Second World War. Was it because of a shortage of raw materials? Was it because of a different need for concealing and camouflage?

I do not pretend to know and understand any aspect of concealing and camouflage of military aircraft – actually I am far from it – but I try to expand my understanding and I hope to have some fruitful conversations with the readers of my articles. I will publish articles in loose order when I have enough content to share, this will sure take months or even a year or so. Please feel free to use the commentary function below each article for a public discussion for the benefit for all interested in this topic.

Chapter One: Spatial perception

A »spatial perception« is a creation and the result of complex and integrative processes in the human brain.
Spatial perception is based on several different spatial features in the visual field of the observer. Depending on the actual scenery in the visual field of the observer these spatial features have a varying strength and influence on the spatial perception of the observer. Spatial perception is the result of a combination and interaction of several different visual and spatial features.

Part 1: Contrast and Resolution

Part 1 of Chapter One deals with the spatial perception of humans, focusing on those aspects that are important to understand the concealing and camouflage of military aircraft operating in daylight.

The most important spatial information is a difference in color and brightness of adjacent spatial points (contrast) which are within the human visual discrimination (resolution). Differences in brightness and color can be caused through illumination as well as through different properties of spatial points like color, transmission, absorption and reflection.
In a scenery where all spatial points have the same brightness and color and under an ideal and even illumination (no shadows, no gradation in brightness and color) the observer within this setting would be unable of a spatial perception. Spatial elements, i.e. objects, would be invisible.
In a realistic and natural scenery with enough light to enable human vision such a scenario is unrealistic, however. Furthermore differences in brightness are wavelength dependent and would result in differences in color, too.
Conclusion: Differences in color and brightness are the foundation for any spatial perception of human beings. Adjacent spatial points with the same color and brightness are  indistinguishable for the human brain.

Objection – One mosaic piece of concealing: Countershading

When differences in color and brightness of adjacent spatial points allow for a spatial perception, then equality of adjacent spatial points in brightness and color will inhibit a spatial perception in the observer´s brain. This leads us directly to Thayer´s law. US-Naturalist Abott H. Thayer first described the natural law of countershading in 1896.

An object illuminated by direct sunlight reflects light from its upper portion creating the impression of a bright upper side whereas its lower portion receives no direct sunlight resulting in the impression of a dark bottom side. This results in a gradation of brightness and color over the object and thus enables a spatial perception in the observer´s brain.

Countershading of a monochrome cube according to Abott H. Thayer

A: Natural illumination of a monochrome cube by the sun
B: Opposed coloration of the cube
C: Superposition of A and B results in a »flattened« object.

To counteract this spatial perception many animals show an opposed gradation in color and brightness to counteract the effects of a natural illumination. The result is a »flattened« object that has the same color and brightness in every spatial point.

Part 2 of Chapter One will bring us more information on spatial perception of humans, focusing on those aspects that are important to understand the concealing and camouflage of military aircraft operating in daylight. Please check my blog for publication of Part 2 in the comming weeks. Thanks!