The theoretical basis for camouflage is the underlying methodology used in camouflage

Camouflage

Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

, whether natural or human-made. The definition of camouflage involves concealment and obscurity, whether applied to the natural coloration of animals, or the paint schemes used on military vehicles. The methods by which concealment or obscurity are attained share a common set of strategies intended to deceive the observer. Camouflage is not limited to the commonly encountered visual camouflage, but encompasses other senses as well.

The use of camouflage, no matter what the specific application, has certain basic requirements that must be met. First, the camouflage must be tailored to the observer. Second, the camouflage must deceive the observer into making a false judgment about the camouflaged object. The strategies of camouflage can be broken down into up to four categories, which are cryptic, disruptive, mimicry, and countershading. Each of these deals with a different method of deceiving the observer, and often strategies are combined increase their effectiveness. A tiger

Tiger

The tiger is the largest cat species, reaching a total body length of up to and weighing up to . Their most recognizable feature is a pattern of dark vertical stripes on reddish-orange fur with lighter underparts...

's distinctive coloration, for example, uses a combination of countershading and cryptic colors and patterns to blend into its environment.

Human use of camouflage

Humans have been practicing the art of camouflage since prehistoric times, as evidenced by depictions of camouflage use in cave paintings. Among humans, camouflage is of particular importance to the military, where the art of camouflage is as important as marksmanship. United States Army field manual

Field Manual

__FORCETOC__Field Manual is the second solo album by Death Cab for Cutie guitarist Chris Walla, released on January 29, 2008 on Barsuk Records. The album is Walla's first under his own name...

 FM 5-20 states in chapter 1: Camouflage uses concealment and deception to promote our offensive action, to surprise, to mislead the enemy, and to prevent him from inflicting damage upon us. Concealment includes hiding from view, making hard to see clearly, arranging obstructions to vision, deceiving and disguising, and deception involving sound.

Painters and other visual artist

Artist

An artist is a person engaged in one or more of any of a broad spectrum of activities related to creating art, practicing the arts and/or demonstrating an art. The common usage in both everyday speech and academic discourse is a practitioner in the visual arts only...

s are sometimes employed in the development of camouflage, because they often deal with human visual perception, and it was an American artist, Abbott Handerson Thayer

Abbott Handerson Thayer

Abbott Handerson Thayer was an American artist, naturalist and teacher. As a painter of portraits, figures, animals and landscapes, he enjoyed a certain prominence during his lifetime, as indicated by the fact that his paintings are part of the most important U.S. art collections...

, who first published a scientific paper in 1892 describing the countershading technique (see below) often found in natural camouflage. While camouflage has been used for hunting, from when prehistoric hunters dressed in animal skins to mimic their prey, to the Scottish

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 gamekeeper

Gamekeeper

A gamekeeper is a person who manages an area of countryside to make sure there is enough game for shooting, or fish for angling, and who actively manages areas of woodland, moorland, waterway or farmland for the benefit of game birds, deer, fish and wildlife in general.Typically, a gamekeeper is...

s' ghillie suit

Ghillie suit

A ghillie suit, wookie suit, yowie suit, or camo tent is a type of camouflage clothing designed to resemble heavy foliage. Typically, it is a net or cloth garment covered in loose strips of cloth or twine, sometimes made to look like leaves and twigs, and optionally augmented with scraps of foliage...

s still worn by hunters and sniper

Sniper

A sniper is a marksman who shoots targets from concealed positions or distances exceeding the capabilities of regular personnel. Snipers typically have specialized training and distinct high-precision rifles....

s today, camouflage in a military context was considered effeminate and greeted with scorn in the late 19th century.

Military camouflage did not achieve widespread use until World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, after the introduction of airplanes for observation made its use far more important. French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 gun crews wore smocks smeared with brown and green paint to break up their outlines and provide concealment from the aerial observers; it is likely that the first soldiers to try this were artists serving in the infantry. Upon seeing a camouflaged cannon for the first time, artist Pablo Picasso

Pablo Picasso

Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Cipriano de la Santísima Trinidad Ruiz y Picasso known as Pablo Ruiz Picasso was a Spanish expatriate painter, sculptor, printmaker, ceramicist, and stage designer, one of the greatest and most influential artists of the...

 is reported to have said, C'est nous qui avons fait ca, or it is we who have created that. This early camouflage was not restricted to just coloring, it applied to shape as well; at an early demonstration by the American Camouflage Corps, President Woodrow Wilson

Woodrow Wilson

Thomas Woodrow Wilson was the 28th President of the United States, from 1913 to 1921. A leader of the Progressive Movement, he served as President of Princeton University from 1902 to 1910, and then as the Governor of New Jersey from 1911 to 1913...

 approached within ten feet of a soldier without noticing him. The soldier was in a foxhole covered by a papier-mâché

Papier-mâché

Papier-mâché , alternatively, paper-mache, is a composite material consisting of paper pieces or pulp, sometimes reinforced with textiles, bound with an adhesive, such as glue, starch, or wallpaper paste....

 cover camouflaged as a rock.

Camouflage in nature

Many animals possess some form of camouflage, for many reasons. Natural camouflage can involve many different senses, including sight, smell, touch, and sound. The reasons for camouflage are primarily to deceive predators or prey, but camouflage can serve to aid reproduction. Some animals are even capable of adapting their appearance to match their environment. A few examples of varied strategies in camouflage are:

• Deceiving prey
  • Praying mantises resemble the plants on which they lie in wait, resembling leaves or even flowers
• Deceiving predators
  • Some octopus
    Octopus
    The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...
    
    es behave like a ball of algae
    Algae
    Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
    
    , curling into a ball and rolling along the sea floor
  • Vivid patterns such as the zebra
    Zebra
    Zebras are several species of African equids united by their distinctive black and white stripes. Their stripes come in different patterns unique to each individual. They are generally social animals that live in small harems to large herds...
    
    's stripes serve to confuse predators' perceptions, allowing the zebra to escape capture
• Adaptive camouflage
  • Some animals, such as the Arctic Fox
    Arctic fox
    The arctic fox , also known as the white fox, polar fox or snow fox, is a small fox native to Arctic regions of the Northern Hemisphere and is common throughout the Arctic tundra biome. The Greek word alopex, means a fox and Vulpes is the Latin version...
    
    , moult
    Moult
    In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
    
     to change color with the seasons

Strategies of camouflage

Camouflage is an attempt to avoid observation, and as such, it is tailored to the vision of the expected observer. In military contexts, in particular, this is not limited to normal biological vision, but applies to night vision systems, radar, and arguably sonar as well. Camouflage strategies can be broken down into four categories: cryptic (or blending), disruptive (or dazzle), mimicry, and countershading. These may be applied individually, or in combination with one another to provide an overall camouflage strategy. For example, the blending of disruptive and cryptic coloration is called coincident disruption.

Cryptic

Cryptic camouflage is an attempt to blend into the environment and become effectively imperceptible. To do this, the camouflaged object must minimize observable differences between itself and the background with respect to the senses of the target observer. The definitive example of camouflage is a cryptic camouflage designed to match the visual appearance of the expected background, generally using a mottled pattern of greens and browns to match ground and foliage color and break up the outline of the camouflaged object.

Disruptive

Disruptive camouflage is not intended to blend into the environment, and in fact often involves bright, eye-catching colors that would be the antithesis of cryptic camouflage. Disruptive camouflage seeks to confuse the observer, by providing visual cues that override the camouflaged object's features. This prevents the observer from accurately identifying characteristics of the camouflaged object(s), such as shape, size, orientation, and number of objects in a group.

Camouflage by Mimicry

Mimicry as camouflage is the attempt by the camouflaged object to be observed as some other type of object. Many forms of mimicry do not constitute camouflage: for example, a Hoverfly

Hoverfly

Hoverflies, sometimes called flower flies or syrphid flies, make up the insect family Syrphidae. As their common name suggests, they are often seen hovering or nectaring at flowers; the adults of many species feed mainly on nectar and pollen, while the larvae eat a wide range of foods...

 which mimics a stinging Wasp

Wasp

The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...

 is clearly visible to potential predators.

Some insects have extremely effective mimetic camouflage, as in the stick insects (Phasmatodea

Phasmatodea

The Phasmatodea are an order of insects, whose members are variously known as stick insects , walking sticks or stick-bugs , phasmids, ghost insects and leaf insects...

), which take the form of twigs, bark, leaves or lichens.

Vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s that use mimicry for camouflage include leaf-mimic frogs, leaf-tailed geckos and leaf fish.

Countershading

Also called Thayer's Law, a tribute to the artist who first described it, countershading is the process of using lighter colors on normally dark areas, and darker colors on normally light areas. This removes some of the visual cues used for depth perception

Depth perception

Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....

, causing the countershaded object to appear flat, rather than as an object with depth.

Military doctrine sometimes applies countershading, suggesting the use of dark paint for bright areas of the face, light paint for shadowed areas, and combining this with a disruptive pattern over large areas of skin.

Visual elements of camouflage

Eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

s differ widely across the animal kingdom. Some animals see in monochrome, perceiving only brightness, while other see two or, like humans, three types of color; some species of bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s and reptile

Reptile

Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s are capable of distinguishing four different colors. Even in animals with the same degree of color perception, the pigment

Pigment

A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

s respond to different wavelength

Wavelength

In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...

s, meaning what would appear to be a metamer

Metamerism (color)

In colorimetry, metamerism is the matching of apparent color of objects with different spectral power distributions. Colors that match this way are called metamers....

 to one species would be a completely different color to another species.

In addition to differences in how color is perceived, the nervous system

Nervous system

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...

 does a significant amount of processing to the image, finding edges, adjusting contrast, and determining spatial frequency.

Perception of color and brightness

Normal humans (excluding individuals who have a form of colorblindness) see though the actions of four types of receptors in the eye; the rods, which are highly sensitive, perceive brightness, while three types of cones perceive red, green, and blue colors. Humans, and most primates, are trichromats, able to perceive three types of color. The density and sensitivity of these rods and cones determine how sensitive the eye is to color. Brightness is the most important factor, followed by green, red, and blue colors, in that order. Sometimes unexpected colors provide good cryptic coloration, such as pink. A shade called Mountbatten pink

Mountbatten pink

Mountbatten Pink, also called Plymouth Pink, is a naval camouflage colour, a shade of grayish mauve, invented by Louis Mountbatten of the British Royal Navy in autumn 1940 during World War II....

 was used during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 for ships when it was discovered that it disappeared against the morning and evening skies, and the Special Air Service

Special Air Service

Special Air Service or SAS is a corps of the British Army constituted on 31 May 1950. They are part of the United Kingdom Special Forces and have served as a model for the special forces of many other countries all over the world...

 used pink as the primary color on the desert

Desert

A desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...

 camouflaged Land Rover Series IIA patrol vehicles, leading to the nickname The Pink
Panthers.

Color perception in animals varies by species; most mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s are dichromats, perceiving two colors. Deer

Deer

Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...

, for example, see blue and yellow, but not red, and their perception of blue is far broader and more acute than humans. A camouflage garment laundered in typical laundry detergent laced with ultraviolet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 dye

Dye

A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....

, added to brighten colors, may blend into the background when seen with the human eye, but the deer's eyes are sensitive into the near ultraviolet portion of the spectrum, and the garment will stand out as a brightly colored object. Orange and red, however, are far enough from the deer's yellow receptor range that they will appear as dim colors, so what a human sees as a bright orange element in a camouflage pattern will appear as a dark color to the deer's eye. Similarly, the rods of deer are sensitive further into the near ultraviolet than are human eyes (though still lacking in response at the red end of the spectrum), and provide a greater response. This gives
deer superior vision in low light conditions. Birds, on the other hand, do see red, and near ultraviolet; both ultraviolet dyes and blaze orange will be visible to them.

Perception of shapes and edges

Spatial frequency

Spatial frequency

In mathematics, physics, and engineering, spatial frequency is a characteristic of any structure that is periodic across position in space. The spatial frequency is a measure of how often sinusoidal components of the structure repeat per unit of distance. The SI unit of spatial frequency is...

 perceptors in the eyes of many animals allow easy identification of mismatched spatial frequencies. By matching the spatial frequency of the background, such as a tiger's stripes, the camouflaged object can blend in; by not matching it, such as with the zebra's stripes, the camouflaged object can stand out.

Perception of movement

Vision, in animals from flies

Housefly

The housefly , Musca domestica, is a fly of the suborder Cyclorrhapha...

 to humans, has special processing mechanisms for detection of motion. Motion will destroy the illusion of even otherwise perfect cryptic camouflage, so objects relying on cryptic camouflage must remain very nearly stationary with respect to their environment. This does not apply to other camouflage strategies; the disruptive form of camouflage, for example, was applied to ships in the form of dazzle camouflage, providing a more effective camouflage for the moving ships than a cryptic strategy. Octopus ink and smoke screens are other forms of camouflage that can effectively be used to conceal movement.

Non-vision camouflage

Many animals rely far more on senses other than sight, so when attempting to deceive these animals, it is important to consider other senses. An example of this is the wide range of products available to the hunter to deal with the issue of scent. These can range from scent blocking clothing, which serves as a cryptic form of camouflage, to scents that mimic plant, animal, and food scents, designed to mask the hunter's scent or lure the game in.

Clothing can also provide a cryptic camouflage with respect to sound. Certain fabrics, such as cotton

Cotton

Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....

/nylon

Nylon

Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...

 blends, create a significant amount of sound when rubbed together, or against other objects. Other fabrics, such as polar fleece

Polar fleece

Polar fleece, usually referred to simply as "fleece," is a soft napped insulating synthetic fabric made from Polyethylene terephthalate or other synthetic fibers. One of the first forms was Polar Fleece created in 1979 by Malden Mills, now Polartec LLC., a new, light and strong pile fabric meant...

 and many all natural fiber fabrics, are much quieter, and will reduce the amount of noise generated by movement. Game calls are used as a form of mimicry, with calls existing that mimic the sounds of everything from duck

Duck

Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...

s and geese

Goose

The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....

 to bear

Bear

Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

s and coyote

Coyote

The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...

s. These calls range from simple reed instruments that mimic a duck's quack to remote controlled electronic playback devices that provide the user with a menu-driven selection of digitally recorded sounds.

Camouflage against technological observation

Radar

Radar

Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

, sonar

Sonar

Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

, night vision

Night vision

Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range...

, and thermal imaging are all common forms of observation, and just like natural senses, camouflage exists in many forms to deceive these technological senses. Camouflage may be implemented by means such as stealth technology

Stealth technology

Stealth technology also termed LO technology is a sub-discipline of military tactics and passive electronic countermeasures, which cover a range of techniques used with personnel, aircraft, ships, submarines, and missiles, to make them less visible to radar, infrared, sonar and other detection...

 applied to military vehicles. Camouflage clothing can help defeat technological detection such as by night vision devices. Thermal camouflage cream may reduce infrared emissions from bare skin.

Adaptive camouflage

Chameleons and some octopuses have the ability to alter their color through the use of chromatophores which allow the animal to change the type and amount of light reflected. This is a form of adaptive or active camouflage. Research is being done into military adaptations of adaptive cryptic camouflage, using sensors and adaptive coloration to sense and adapt the coloration of an object to better match its background.