Color - body, used, process, chemical, form, energy, air, parts, effects Color Color Photo by: SSilver Color is a property of light that depends on the frequency of light waves. Frequency is defined as the number of wave segments that pass a given point every second. In most cases, when people talk about light, they are referring to white light. The best example of white light is ordinary sunlight: light that comes from the Sun. Light is a form of electromagnetic radiation: a form of energy carried by waves. The term "electromagnetic radiation" refers to a vast range of energy waves, including gamma rays, X rays, ultraviolet rays, visible light, infrared radiation, microwaves, radar, and radio waves. Of all these forms, only one can be detected by the human eye: visible light. White light and color White light (such as sunlight) and colors are closely related. A piece of glass or crystal can cause a beam of sunlight to break up into a rainbow: a beautiful separation of colors. The technical term for a rainbow is a spectrum. The colors in a spectrum range from deep purple to brilliant red.

One way to remember the colors of the spectrum is with the mnemonic device (memory clue) ROY G. BIV, which stands for Red, Orange, Yellow, Green, Blue, Indigo, and Violet. English physicist Isaac Newton (1642–1727) was the first person to study the connection between white light and colors. Newton caused a beam of white light to fall on a glass prism and found that the white light was broken up into a spectrum. He then placed a second prism in front of the first and found that the colors could be brought back together into a beam of white light. A rainbow is a naturally occurring illustration of Newton's experiment. Instead of a glass prism, though, it is tiny droplets of rainwater that cause sunlight to break up into a spectrum of colors, a spectrum we call a rainbow. Color and wavelength The word "color" actually refers to the light of a particular color, such as red light, yellow light, or blue light. The color of a light beam depends on just one factor: the wavelength of the light. Wavelength is defined as the distance between two exactly identical parts of a given wave.

Red light consists of light waves with a wavelength of about 700 nanometers (billionths of a meter), yellow light has wavelengths of about 550 nanometers, and blue light has wavelengths of about 450 nanometers. But the wavelengths of colored light are not limited to specific ranges. For example, waves that have wavelengths of 600, 625, 650, and 675 nanometers would have orange, orangish-red, reddish-orange, and, finally, red colors. Words to Know Color: A property of light determined by its wavelength. Colorant: A chemical substance—such as ink, paint, crayons, or chalk—that gives color to materials. Complementary colors: Two colors that, when mixed with each other, produce white light. Electromagnetic radiation: A form of energy carried by waves. Frequency: The number of segments in a wave that pass a given point every second. Gray: A color produced by mixing white and black. Hue: The name given to a color on the basis of its frequency. Light: A form of energy that travels in waves.

Nanometer: A unit of length; this measurement is equal to one-billionth of a meter. Pigment: A substance that displays a color because of the wavelengths of light that it reflects. Primary colors: Colors that, when mixed with each other, produce white light. Shade: The color produced by mixing a color with black. Spectrum: The band of colors that forms when white light is passed through a prism. Tint: The color formed by mixing a given color with white. Tone: The color formed by mixing a given color with gray (black and white). Wavelength: The distance between two exactly identical parts of a wave. The color of objects Light can be seen only when it reflects off some object. For example, as you look out across a field, you cannot see beams of light passing through the air, but you can see the green of trees, the brown of fences, and the yellow petals of flowers because of light reflected by these objects. To understand how objects produce color, imagine an object that reflects all wavelengths of light equally. When white light shines on that object, all parts of the spectrum are reflected equally. The color of the object is white.

(White is generally not regarded as a color but as a combination of all colors mixed together.) Now imagine that an object absorbs (soaks up) all wavelengths of light that strike it. That is, no parts of the spectrum are reflected. This object is black, a word that is used to describe an object that reflects no radiation. Finally, imagine an object that reflects light with a wavelength of about 500 nanometers. Such an object will absorb all wavelengths of light except those close to 500 nanometers. It will be impossible to see red light (700 nanometers), violet light (400 nanometers), or blue light (450 nanometers) because those parts of the spectrum are all absorbed by the object. The only light that is reflected—and the only color that can be seen—is green, which has a wavelength of about 500 nanometers. Primary and complementary colors White light can be produced by combining all colors of the spectrum at once, as Newton discovered. However, it is also possible to make white light by combining only three colors in the spectrum: red, green, and blue. For this reason, these three colors of light are known as the primary colors.

(For more on the concept of primary colors, see subhead titled "Pigments.") In addition to white light, all colors of the spectrum can be produced by an appropriate mixing of the primary colors. For example, red and green lights will combine to form yellow light. It is also possible to make white light by combining only two colors, although these two colors are not primary colors. For example, the combination of a bluish-violet light and a yellow light form white light. Any two colors that produce white light, such as bluish-violet and yellow, are known as complementary colors. The language of colors A special vocabulary is used to describe colors. The fundamental terms include: Hue: The basic name of a color, as determined by its frequency. Light with a wavelength of 600 nanometers is said to have an orange hue. Gray: The color produced by mixing white and black. Shade: The color produced by mixing a color with black. For example, the shade known as maroon is formed by mixing red and black. Tint: The color formed by mixing a color with white. Pink is produced when red and white are mixed. Tone: The color formed by mixing a color with gray (black and white).

Red plus white plus black results in the tone known as rose. Pigments A pigment is a substance that reflects only certain wavelengths of light. Strictly speaking, there is no such thing as a white pigment because such a substance would reflect all wavelengths of light. A red pigment is one that reflects light with a wavelength of about 700 nanometers; a blue pigment is one that reflects light with a wavelength of about 450 nanometers. The rules for combining pigment colors are different from those for combining light colors. For example, combining yellow paint and blue paint produces green paint. Combining red paint with yellow paint produces orange paint. And combining all three of the primary colors of paints—yellow, blue, and red—produces black paint. An array of bright colors. (Reproduced by permission of The Stock Market .) Other color phenomena Color effects occur in many different situations in the natural world. For example, the swirling colors in a soap bubble are produced by interference, a process in which light is reflected from two different surfaces very close to each other. The soap bubble is made of a very thin layer of soap: the inside and outside surfaces are less than a millimeter away from each other.

When light strikes the bubble, then, it is reflected from both the outer surface and from the inside surface of the bubble. The two reflected beams of light interfere with each other in such a way that some wavelengths of light are reinforced, while others are canceled out. It is by this mechanism that the colors of the soap bubble are produced. Glossary of Color Terms Dimensions of Color Chromaticity: Think about a color's "purity" when describing its "chromaticity" or " CHROMA ". This property of color tells us how pure a hue is. That means there is no white, black, or gray present in a color that has high chroma. These colors will appear very vivid and well, ... pure. This concept is related to and often confused with saturation. However, we will continue to use these terms separately because they refer to distinct situations, as explained here. High Chroma - very shiny, vivid Low Chroma - achromatic, no hue Constant Chroma - medium chroma Similar vividness despite differences in hue; less purity than top image. Saturation: Related to chromaticity, saturation tells us how a color looks under certain lighting conditions.

For instance, a room painted a solid color will appear different at night than in daylight. Over the course of the day, although the color is the same, the saturation changes. This property of color can also be called intensity. Be careful not to think about SATURATION in terms of light and dark but rather in terms of pale or weak and pure or strong. Saturation Const. - same intensity, different hues Saturation Contrast - various levels of fullness, same hue Value: When we describe a color as "light" or "dark", we are discussing its value or "brightness". This property of color tells us how light or dark a color is based on how close it is to white. For instance, canary yellow would be considered lighter than navy blue which in turn is lighter than black. Therefore, the value of canary yellow is higher than navy blue and black. Click here to find out why humans are very sensitive to a color's VALUE /BRIGHTNESS.

Low Value, Constant - same brightness level Contrast of Value - grayscale = no chroma Contrast of Value - stark differences in brightness Luminance: Although brightness is often used interchangably with luminance, we prefer to use the term "lightness." This concept deals with many of the same variables as value but using a different mathematical equation. Check out our own definition of LUMINANCE /LIGHTNESS or more simply, think about the Color Wheel as colors having equal luminance. Adding white will increase lightness and adding black will decrease it. Go to the Dimensions of Color Screensaver for an illustrated example. Tints, Tones and Shades: These terms are often used inappropriately but they describe fairly simple color concepts. The important thing to remember is how the color varies from its original hue. If white is added to a color, the lighter version is called a "tint". If the color is made darker by adding black, the result is called a "shade".

And if gray is added, each gradation gives you a different "tone." Tints (adding white to a pure hue) Shades (adding black to a pure hue) Tones (adding gray to a pure hue) Complementary Colors: When two or more colors "go together," they are said to be "complementary." This is completely subjective and open to interpretation and differences in opinion. A more exact definition is "any two colors that, when mixed together produce a neutral gray (paints/pigments) or white (light). Primary Colors: This definition really depends on what type of medium of color we are using. The colors that are seen when sunlight is split by a prism are sometimes called the spectral colors. These are red, orange, yellow, green, blue, indigo, and violet. These ROYGBIV colors are often reduced to three "red, green, and blue-violet" which are the primary colors for the additive color system (light). The primary colors for the subtractive color system (paint/pigment) are "cyan, magenta and yellow." Notice that "red, yellow and blue" should never be used as the combination for color primaries!

RGB, CMYK, HSL: Different color systems are used for different color conditions depending on how the color is created. When using projected light, RGB or red/green/blue, is the governing system. For color that is mixed with paints, pigments or inks on fabric, paper, canvas or some other material, CMY or cyan/magenta/yellow, is the color model. Because these pure pigments tend to be quite expensive, Black, symbolized by "K", is substituted for equal parts of CMY to lower costs of ink. Another major color system is HSL or hue/satuation/lightness. This system has many variants switching saturation with chroma, luminance with value etc. but is usually consistent with how the human eye sees color. GAM : Lighting Equipment For Architectural, Specialty & Theatrical Effects GAM PRODUCTS, INC. • Tel:(323) 935.4975 • Fax:(323) 935.2002 The Language of Additive and Subtractive Color Mixing by Joseph N. Tawil Few subjects are more difficult to articulate than color.

Describing colors and color mixing systems is a minefield of linguistic problems, not the least of which is the confusion between ADDITIVE and SUBTRACTIVE color mixing. The purpose of this article is to lend clarification and understanding about the language employed that describes these two color mixing theories. Additive Color Mixing Color mixing with light is called ADDITIVE Color Mixing. This tri-color mixing theory was proposed by Sir Thomas Young in the early 1800's and it is the basis for all film and video color systems today. Young discovered that by mixing red, blue and green light he could make most of the colors in the visible spectrum. Young determined that red, green and blue were the ideal primary colors of light because they allow for the widest variety and create a reasonable "white". Red, green and blue are three colors which are widely separated from each other and because of this they will combine to make many other colors including in the right circumstances, "white". Combining any two primary colors creates a secondary color which is a complement of the third primary (complement as in completes). For example, by combining red and blue you get magenta and other colors in the violet and pink range. Combining blue and green generates cyan (blue-green) colors.

Combining red and green creates yellow and other colors in the orange range. Complementary colors are also called secondary colors. Violets and pinks are complementary to the primary color green because they contain red and blue. Oranges and yellows are complementary to the primary color blue because they contain red and green. Tri-color mixing is illustrated in Chart I. It is interesting to note that the complementary colors (or secondary colors) created in the ADDITIVE color mixing process cyan, yellow and magenta, are the primary colors of the SUBTRACTIVE color mixing system. Obviously, this is not an accident and the two theories do tie together. SUBTRACTIVE COLOR FILTERS SUBTRACTIVE color filtering is something all of us have experienced in elementary school, where we have mixed paints to make a variety of colors. Later on we probably read some art books where painters talked about mixing primaries to make different colors. The primaries are often described in these art books as red, yellow and blue. Film makers however see the SUBTRACTIVE color mixing primaries described as yellow, cyan, and magenta. Using the same language to describe primary colors in both the SUBTRACTIVE and ADDITIVE color mixing process causes a great deal of confusion.

Printers and film makers define the SUBTRACTIVE primary colors more accurately as cyan, yellow and magenta (CYM) separating them from the ADDITIVE color process. In SUBTRACTIVE color mixing as we mix the primary colors of paints, inks (or filter emulsion layers) the resulting color is darker and darker and eventually black. In order to be visible an object must give off light. The object might be an actual light source or a reflective light source. Objects that do not produce light are colored by a "color subtraction" process. When "white" light strikes the object some colors are absorbed and others are reflected. Pigments, paints, dyes and inks make color by subtracting a part of the visible spectrum. The process is known as SUBTRACTIVE color mixing. The color mixing charts shown above illustrate the two sets of "terms" used to describe SUBTRACTIVE color mixing. The confusion created by borrowing the same language of ADDITIVE color mixing (Illustration II) was corrected by adopting the more specific color descriptions, cyan, yellow and magenta (CYM) (Illustration III).

Printers and professionals dealing with color mixing use these names (CYM) so as not to confuse ADDITIVE and SUBTRACTIVE color systems. The term CYMK might also be familiar. In the four color printing process the K represents black. In the film process CYM is used to describe the layers of color emulsions which give us our color photography. Describing the Color of Light (ADDITIVE) Hue, Value and Chroma are terms from the Munsel system of color notation (1905) a system designed for describing color in ink and paint rather than the color of light. However, Munsel¹s three descriptive terms are often used to define the color of light contributing more to the confusion than the clarity of the subject. The vocabulary of color tends to become a minefield of contradictions and confused meanings. Colorimetry is another system for describing color which is of importance because it relates well to describing colored light. In colorimetry the following terms are used to describe the color of light: Dominant Wavelength (DWL), Brightness and Purity. DOMINANT WAVELENGTH: The apparent color of light similar to the term hue meaning the apparent color i.e. red, blue.

BRIGHTNESS: The percentage of transmission of the full spectrum of energy (similar to value) and often described as intensity. PURITY: Similar to chroma in that it describes the mixture of color of the DWL with white, or the color of the light source. If there is only the color of the DWL, it is 100% pure. If there is very little of the DWL in the mixture, (as in a tint) the color would be say 5% pure. BLACK: The absence of all colors. WHITE: The presence of all colors. Describing the Color of an Object (SUBTRACTIVE) Color descriptions for an object are usually dominated by the Munsel system of color notation which popularized certain terms. Hue, value and chroma have become the most frequently used terms for color description. As useful as these terms are, it leaves out one very valuable characteristic, Texture. HUE: Color or color family i.e. red, green blue and yellow. VALUE: The intensity of a color as it is compared to the lightest to the darkest as it ranges from white to black. CHROMA: Saturation or purity of a color from its most vivid pure to its lightest tint.

TEXTURE: The surface properties of a color as in shiny or matte, reflective or diffusing. You can see from these two sets of definitions the terms have somewhat similar meanings but not exactly the same. They can often be confusing when descriptions of the color of an object (SUBTRACTIVE) are used to describe the color of light (ADDITIVE). This is a linguistic problem, not a color theory problem. One set of descriptions is appropriate to describe light or the result of ADDITIVE color mixing. The other is appropriate to describe the color of an object SUBTRACTIVE color mixing. Summary and Conclusion We have reviewed the two theories of color, ADDITIVE and SUBTRACTIVE color mixing. We have noted that the primary colors are different for these two systems. ADDITIVE color mixing uses red, green and blue (RGB). SUBTRACTIVE color mixing uses cyan, yellow and magenta (CYM). The primary colors in the SUBTRACTIVE coloring system are the secondaries of the ADDITIVE color mixing system. These two systems of color mixing are the basis of all film and video color production. Color Theory Color Theory A primary color is a color that cannot be made from a combination of any other colors.

A secondary color is a color created from a combination of two primary colors. Tertiary color is a combination of three colors (primary or secondary). Printers and artists have different definitions for primary colors. The traditionional primary colors that painters have used are red, yellow, and blue. Modern printing press secondary colors are magenta, yellow, and cyan. These two primary color systems obviously do not agree. Additive and subtractive are the two primary methods for reproducing a range of color. Additive Color Additive color synthesis is the creation of color by mixing colors of light. Human vision relies on light sensitive cells in the retina of the eye. There are two basic kinds of sensors. These are rods and cones. Rods are cells which can work at very low intensity, but cannot resolve sharp images or color. Cones are cells that can resolve sharp images and color, but require much higher light levels to work. The combined information from these sensors is sent to the brain and enables us to see. There are three types of cone. Red cones are sensitive to red light, green cones are sensitive to green light, and blue cones are sensitive to blue light. The perception of color depends on an imbalance between the stimulation level of the different cell types.

Additive color processes, such as television, work by having the capability to generate an image composed of red, green, and blue light. Since the intensity information for each of the three colors is preserved, the image color is preserved as well. The spectral distribution of the image will probably be wrong, but if the degree of intensity for each of the primary colors is correct, the image will appear to be the right color. The three primaries in light are red, blue, and green, because they correspond to the red, green, and blue cones in the eye. Example 1 shows how the light from red, green and blue flashlights would appear if shone on a dark wall. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Red + Blue = Magenta Green + Blue = Cyan Printers' primariesï¿½yellow, cyan, and magentaï¿½are typically used by professional designers and printing presses . When all of the colors of the spectrum are combined, they add up to white light.

2 parts Red + 1 part Green = Orange 2 parts Green + 1 part Red = Lime 4 parts Red + 1 part Blue + 1 part Green = Brown Subtractive Color Subtractive color synthesis is the creation of color by mixing colors of pigment, such as paint or ink in your computerï¿½s printer. This type of color is what is used in the art and design world. When learning basic color theory, art students typically use familiar colors like red, yellow, and blue. Subtractive color processes work by blocking out parts of the spectrum. The idea of subtractive color is to reduce the amount of undesired color reaching the eye. If, for example, you had a yellow image, you would want to have a dye that would let red and green reach the eye, and block out blue. The additive secondaries become the printersï¿½ subtractive primaries, because each of the additive secondaries will reflect two of the additive primaries, and absorb one of the additive primaries. The three primaries on the artistsï¿½ color wheel are red, blue, and yellow. Example 2 illustrates subtractive color by showing how primary colors mix on a piece of white paper.

ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Hue ï¿½ Is the name of the color itself, the dominant wavelength of light or the choice of pigment. Lightness (brightness) ï¿½ Is the lightness or darkness of the color, the amoung of light reflected or transmitted. Saturation ï¿½ Is the level of white, black or grey, ranges from neutral to brilliant (pastel to full color). Tint ï¿½ Base color plus white. Tone ï¿½ Base color plus grey. Shade ï¿½ Base color plus black. Value ï¿½ How light or dark a color is. Aggressive - AKA 'Warm'. The yellows, oranges, and reds. These come towards the eye more (spatially) and are generally 'louder' than passive colors. Passive - AKA 'Cool'. The greens, blues, and violets.

These recede from the eye more (spatially) and are generally 'quieter' than the aggressive colors. or Schemes Achromatic ï¿½ï¿½ An achromatic color scheme is one that is colorless ï¿½ using blacks, whites and grays. Complementary ï¿½ A complementary color scheme is one that uses colors directly across from each other on the color wheel. This can be accomplished by using two colors or hues that are opposites such as red and green or violet and yellow. In this color scheme any two complements, all the semi-neutrals and the neutral they produce can be used. Black and white can also be used. Since you can choose from varying colors and hues which can give a bold and dramatic effect, this color scheme isï¿½ best used for dramatic, strong, or bold statements. An example of a complimentary color scheme Monochromatic ï¿½ A monochromatic color scheme is a one-color color scheme. However, the color can be neutralized by adding its complement to lower the intensity of the color. Black and white can also be used to darken and lighten the value of the color.

It is achieved by using one color or hue, utilizing that colorsï¿½ various tints, tones and shades. Using a monochromatic scheme with multiple textures creates character and maintains unity. An example of a monochromatic color scheme Analogous ï¿½ An analogous color scheme is any three adjacent primary, secondary, or tertiary colors on the color wheel. These schemes can be warm or cool. Each can be neutralized by use of its complement, and black and white can be used. Analogous colors "harmonize" well and produce a definite mood to a composition. This can create a very harmonious color scheme. An example of an analogous color scheme Col or Triad ï¿½ A triadic color scheme are colors that are an equal distant from each other on the color wheel. Any three colors equidistant around the color wheel form a triad and can be used in this color scheme (eg., red, yellow and blue). Semi-neutrals are mixed using two of the colors in the triad and the third can be added to further neutralize the pair. Black and white can also be used. This can create a very balanced scheme.

An example of a color triad Col or Tetrad ï¿½ A tetradic color scheme is one using four or more colors on the color wheel (eg., green, violet, red and yellow). Col or Diad ï¿½ A diadic color scheme is one using two colors that are two colors apart on the color wheel (eg., red and orange). Split Complementary ï¿½ A split complimentary color scheme is similar to complimentary but instead of just two colors directly opposite on the color wheel, two of the three colors are adjacent to one of the colors that is opposite. More simply, choose one color and use the color on each side of its complement (eg., blue, yellow-orange and red-orange). Any three adjacent primary, secondary, and tertiary colors can be used, plus the complement of the middle hue. This complement is used subordinately and to produce semi-neutrals of the three colors while maintaining color harmony. Black and white can also be used.

Molecular Expressions: Science, Optics, and You: Light and Color - Primary Colors Home Primary Colors The human eye is sensitive to a narrow band of electromagnetic radiation that lies in the wavelength range between 400 and 700 nanometers, commonly known as the visible light spectrum. This small span of electromagnetic radiation is the sole source of color. All of the wavelengths present in visible light form colorless white light when they are combined, but can be refracted and dispersed into their individual colors by means of a prism. The colors red, green, and blue are classically considered the primary colors because they are fundamental to human vision. All other colors of the visible light spectrum can be produced by properly adding different combinations of these three colors. Moreover, adding equal amounts of red, green, and blue light produces white light and, therefore, these colors are also often described as the primary additive colors. Interactive Java Tutorial Explore how the primary additive colors interact with one another to form new colors. As illustrated by means of the overlapping color circles in Figure 1, if equal portions of green and blue light are added together, the resultant color is cyan.

Similarly, equal portions of green and red light produce the color yellow, and equal portions of red and blue light yield the color magenta. The colors cyan, magenta, and yellow are commonly termed the complementary colors because each complements one of the primary colors, meaning that the two colors can combine to create white light. For instance, yellow (red plus green) is the complement of blue because when the two colors are added together white light is produced. In the same way cyan (green plus blue) is the complement of red, and magenta (red plus blue) is the complement of green light. Interactive Java Tutorial Primary Subtractive Colors Examine how the primary subtractive colors combine to form the primary additives, as well as black, the absence of all color. The complementary colors (cyan, yellow, and magenta) are sometimes alternatively referred to as the subtractive primaries. This is because each one can be formed by subtracting one of the primary additives (red, green, and blue) from white light. For example, yellow light is seen when all blue light is removed from white light, magenta when green is removed, and cyan when red is removed.

Consequently, when all three of the subtractive primary colors are combined, all of the additive primary colors are subtracted from white light, which results in black, the absence of all color. Thus far this discussion has centered on the properties of visible light with respect to the addition and subtraction of transmitted visible light, which is often visualized on the screen of a computer or television. Most of what is actually seen in the real world, however, is light that is reflected from surrounding objects, such as people, buildings, automobiles, and landscapes. These objects do not produce light themselves, but emit color through a process known as color subtraction in which certain wavelengths of light are subtracted, or absorbed, and others are reflected. For instance, a cherry appears red in natural sunlight because it is reflecting red wavelengths and absorbing all other colors. The series of photographs presented below in Figure 2 helps further illustrate this concept. In the first photograph on the left, a playing card, a green bell pepper, and a cluster of purple grapes are illuminated with white light and appear as one would expect to see them under natural lighting. In the second photograph, however, the objects are illuminated with red light.

Note that the playing card reflects all of the light that strikes it, while only the grape stem and highlights on the grapes and pepper reflect the red light. The majority of the red light is being absorbed by the grapes and pepper. The third photograph shows the objects under green illumination. The different radiation wavelength causes the symbols on the playing card to appear black and the body of the card to reflect green light. The grapes reflect some green light, while the pepper appears normal, but with green highlights. The fourth photograph illustrates the objects under blue illumination. In this situation, the grape cluster appears normal with blue highlights, but the stem is invisible because it blends into the black background. The body of the playing card reflects blue light and the symbols appear black, while the pepper only reflects blue light as highlights. Interactive Java Tutorial Color Filters Investigate how color filters operate to alter the apparent color of objects visualized under white light and monochromatic illumination. The human eye can perceive very slight differences in color and is believed to be capable of distinguishing between 8 to 12 million individual shades. Yet, most colors contain some proportion of all wavelengths in the visible spectrum. What really varies from color to color is the distribution of those wavelengths.

The predominant wavelengths of a color determine its basic hue, which can be, for example, purple or orange. It is the ratio of the dominant wavelengths to other wavelengths, however, that determines the color saturation of the sample and whether it appears pale or deeply saturated. The intensity of the color and reflectivity of the object being imaged, on the other hand, determine the brightness of the color, which controls, for instance, whether something appears dark or light blue. Over the years, various classification systems have been devised to systematically express color in terms of these concepts. One of the most widely accepted has been the Munsell Color Tree, which appears below in Figure 3. As illustrated, each color in this system is represented by a distinct position on the tree. Hue color value is represented by placement on the circumference, saturation by the horizontal distance of the color from the central axis, and brightness by the vertical position on the trunk. When learning about color, it is also important to consider pigments and dyes, which are responsible for much of the color that appears on Earth.

For instance, the natural protein pigments that are contained in eyes, skin, and hair reflect and absorb light in such a way that creates a beautiful diversity of appearances in the human race. In order to achieve a similar diversity of color in inanimate objects, such as automobiles, airplanes, and houses, they are frequently coated with pigment-containing paints and portray different shades through the process of color subtraction. Printed items, such as books, magazines, signs and billboards, create colors in the same fundamental way, but through the help of dyes or inks, rather than pigments. All color photographs, and other images that are printed or painted, are produced using just four colored inks or dyes--magenta, cyan, yellow (the subtractive primaries) and black. Mixing inks or dyes of these colors in differing proportions can produce the colors necessary to reproduce almost any image or color. The three subtractive primaries could, in theory, be used alone. However, the limitations of most dyes and inks make it necessary to add black to achieve true color tones.

When an image is being prepared for printing in a book or magazine, it is first separated into the component subtractive primaries, either photographically or with a computer as illustrated above in Figure 4. Each separated component is then made into a film that is used to prepare a printing plate for that color. The final image is created by sequentially printing each color plate, one on top of another, using the appropriate ink to form a composite that recreates the appearance of the original. Paint is produced in a somewhat similar manner. Again, only the subtractive primaries and black are required. Base pigments containing these colors are mixed together to form the various colors used in final paint preparations. Interactive Java Tutorial Color Separation Discover how the subtractive primaries are separated from an image and are made into color plates that can be used to produce realistically colored prints. A clear understanding of the color concepts previously discussed is extremely important when using a microscope to view and capture color images. Microscope light sources are usually tungsten-halogen bulbs that can emit a bright light with a color temperature around 3200 Kelvin. To the observer, this appears as white light that can be absorbed, refracted, reflected, polarized, and/or transmitted by a specimen on the microscope stage.

The rules of primary colors apply to how the specimen interacts with microscope light and what colors are displayed as the sample is visualized in the eyepieces. The same rules also apply to the film used to capture photomicrographs. Contributing Authors Mortimer Abramowitz - Olympus America, Inc., Two Corporate Center Drive., Melville, New York, 11747. Shannon H. Neaves and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310. Introduction to color Introduction to Color Why people are confused There's hardly an everyday subject about which people have more confusion and mis-information than color. Even professional scientists are often — perhaps I should even say “usually” — confused about color. The main cause of this widespread confusion is the misinformation we're all fed in grade school. But that really only pushes the question back a step: why are schoolteachers so confused about color? Complexity I think there are two reasons. One is that color is by no means as simple a subject as it appears. For example, there are two kinds of color mixing (additive and subtractive).

Worse yet, our earliest experiences with color usually are concerned with common technologies like paints or watercolors or crayons; but these media involve a complex mixture of both additive and subtractive color mixing. So our everyday experiences with color can't be analyzed in a simple way. No wonder we're misled by it. Terminology The second problem — related to the first — is that our everyday vocabulary of color names is both inadequate and ambiguous. For example, it fails to allow for the three different dimensions of color: we just have a number of named categories (like red, green, blue, purple, white, black, brown, …) that involve different dimensions of color, without distinguishing between them. So we need to have names for the dimensions of color space before we can discuss colors sensibly. Worse yet, discussions of color are often confined to two-dimensional surfaces: the pages of books, school blackboards, computer screens. That makes it even harder to think of color as three-dimensional, because one of the three dimensions has to be suppressed to fit on the two-dimensional surface we're looking at.

Three dimensions So let's adopt some terms to describe the three aspects or dimensions of color, right here: Hue: Hue is the quality that distinguishes red, green, blue, and so on. Saturation: Saturation is the quality that distinguishes red, pink, and gray of the same hue and brightness. Here's a picture of a pink wedge to illustrate this point: Saturation is sometimes described as the “colorfulness” of a color — i.e., how much it differs from gray. Saturation corresponds to what's called chroma in the Munsell system for denoting surface colors. Brightness: Brightness is the quality that distinguishes white, gray, and black. Sometimes the word lightness is used for something like this. (Unfortunately, both words are sometimes also used to imply saturation.) Brightness corresponds to what's called value in the Munsell system. Continuity Common usage misleads us in another way. Lots of color names refer to particular objects or materials: orange, lime, indigo and violet, for example.

Having a modest number of distinct, named color categories — associated with distinct crayons or paints or objects from our earliest experience — distracts our attention from the fact that color space is continuous: there is a smooth progression of hues from reds through oranges and yellows, and so on. But our words (as well as our teachers) mislead us into thinking there are just a few “colors” that are somehow distinct. This confusion is compounded by teachers' insistence on three “primary” colors — usually incorrectly chosen as red, yellow, and blue — which doesn't really agree with everyday experience. What we do experience in everyday life is the existence of six unique colors that define the ends of three directions in color space: the complementary hue pairs red and green, and blue and yellow; and the unique ends of the brightness dimension, namely white and black. Ambiguous usage Another semantic difficulty is that the word “color” is used in conflicting ways in English. Sometimes we use it to describe all possible parts of color space; but in common usage, “color” usually refers to just one aspect of color, namely, hue (which is what distinguishes red from blue and green and yellow).

This conflicting usage of the word color leads to fruitless arguments about whether black and white are colors. More confusion is caused by failure to distinguish between color and other aspects of appearance, like luster, texture, and transparency. That leads people to think there are colors named “silver” and “gold”, when these terms really refer to a white or yellow color combined with metallic luster (i.e., strong specular reflection). Still more confusion follows from a failure to distinguish between the physical stimuli that elicit sensations of color, and the sensations themselves. We're accustomed to attribute colors to objects, rather than our responses to them: a blue book, a red chair, and so on. This sloppy habit is reinforced by the phenomenon of “color constancy”: the perception of nearly the same color in an object, even when seen under a variety of different illuminations (daylight, twilight, artificial light, … ) that produce very different physical stimuli. Finally, color is so important in so many fields that conflicting terminology has grown up in different areas: art, photography, color printing, television, and so on. So each field has its own set of words to describe the dimensions of color; even experts who understand color have difficulty understanding one another.

Common misconceptions Primary colors If you were taught in school that the three primary colors are red, yellow, and blue, forget it. That's wrong. Color space is 3-dimensional, all right. But before we can talk about primary colors, we need to ask what we want that term to mean. Usually, the idea is that there are 3 colors that can be “mixed” together to form others. But there are different ways to mix colors. Additive primaries What your computer screen does is to add together the light from three different kinds of phosphor (or other light sources). Here they are, one by one: When we add them in pairs we get this: The bright, sky-like blue made by adding the green and dark-blue primaries is called “cyan” in the color business. Red added to blue light makes magenta, a more familiar color. And — surprisingly, to many people — red light added to green light makes yellow. And all 3 together make the white background behind this text: White = Red + Green + Blue Subtractive primaries But if you take pieces of colored glass or plastic, each colored piece removes some colors from white light. For example, a red filter absorbs blue and green, leaving only red.

A green filter removes red and blue; and so on. Obviously, if we stack up a red filter and a green filter, the red one removes the green light, and the green one removes the red light, and they both remove blue light; so we're left with no light at all (assuming the filters are perfect). In subtractive color mixing, red + green = black. So the additive primaries aren't useful for subtractive color mixing. To make subtractive primaries, we need filters that only take out (i.e., subtract) one of the additive primaries at a time, leaving the other two. So if we start with white light (all 3 additive primaries together) and: Remove red: White − Blue = (Red + Green + Blue) − Blue = (Red + Green) So that's yellow, or “minus blue”. So the subtractive primaries are cyan, magenta, and yellow. Now, how do these subtractive primaries combine? Suppose we take cyan and magenta filters and superimpose them. The cyan takes out the red; the magenta takes out the green; what's left is the blue-violet — the “blue” additive primary.

Similarly, yellow plus magneta leaves red; and yellow plus cyan leaves green. The subtractive primaries, paired up, produce the additive primaries. Cyan, magenta, and yellow are the (transparent) inks you'll find in a color printer. Color printing with inks that filter out colors is subtractive color mixing; the inks act like filters. Complementary colors You probably noticed that for every additive primary, there's a corresponding subtractive primary formed by removing that additive primary from white. For example, yellow is (minus blue); so blue and yellow are complementary colors. The other complementary primary pairs are green and magenta, and red and cyan. Notice that white can be produced by adding two complementary colors. In fact, this is really the basis of the idea of complements: any two colors that can be added (in the proper proportions) to give white are complements. They don't need to be primaries. Mixing paints Now, what happens when we mix paints instead of inks? Mixing paints certainly isn't additive; if it were, you could mix red and green paint to get yellow, as we did above with the computer screen. But as everyone knows, red and green paint mixed produce a muddy brown.

That's not too far from the black we'd expect from subtractive mixing. But paints aren't exactly subtractive, either. When you stack filters, you get the same transmission regardless of the order in which the light goes through them. But if you paint one color on top of another, you see mostly the top color. Paints contain little particles of colored pigment. The little bits of pigment absorb some light and transmit some light, but they also scatter some light. So paints aren't either purely additive or purely subtractive; the two kinds of color mixing are combined in a complicated way. But usually the subtractive part dominates the mixture. (Crayon colors do much the same sort of thing.) Notice that cyan is somewhat like a light blue; so if you ignore the difference between red and magenta, the subtractive primaries might almost be called “red, yellow, and blue”. This is where the story that red, yellow and blue are primary colors of paint came from. But, if you've ever mixed paints, you know this isn't the true story.

About the only part of the schoolroom story that works is mixing blue and yellow to get green; and that works, because what's touted as “blue” in school paints or crayons is usually a greenish blue, close to cyan. And, subtractively, cyan plus yellow (which removes the blue-violet part) leaves green. The situation is complicated by the fact that the pigments available to produce colored paints are far from ideal. They don't remove just one additive color, but take out some of each. Usually, the absorption is strongest in the blue and violet, so subtractive combinations end up being a very dark yellow or orange. Brown But what's a dark yellow or orange? Here you see them: The yellow square, like the one shown at the left, was generated in PostScript by telling the computer to display both the red and green phosphors at maximum intensity. The orange square to its right was made by asking for full Red intensity and half Green. The two squares below were produced just by asking for half as much of everything. You can see that the darker yellow appears olive green, and the darker orange, brown. The names“yellow” and“orange”are used only for colors of those hues with high brightness.

Darker colors of the same hue and saturation are called“olive”and“brown”. Incidentally, what the human visual system considers “light” or “dark” depends very strongly on the perceived context. If I had displayed the orange square here against a white background instead of a medium-gray one, you'd have perceived it as brown rather than orange. There are some vivid demonstrations of this context effect at Edward Adelson's checker-shadow illusion , cut-the-knot.org , and the paper by R. Beau Lotto and Dale Purves, “An empirical explanation of color contrast” (Pub. National Acad. Sci. 97, 12834–12839 (2000), which you can download as a PDF file if your institution subscribes to PNAS. The most striking demonstration, by Al Seckel at Caltech, is currently off-line. Purple The color that was called “magneta” above is an example of a class of non-spectral colors called purple. (The term “non-spectral” means that these colors do not appear in a spectrum .) The purples are complementary to various shades of green.

Colors of the rainbow Rainbows are natural spectra — although they're relatively insipid ones, compared to what can be seen in an optics laboratory, or displayed on a computer monitor. What's important here is that “all the colors of the rainbow” does not include all the colors: the purples are missing. And of course the dark colors, like brown and olive, aren't in rainbows, either. Where to learn more There's a great set of Web pages on color at , starting with the page on color vision . This material is all written from the point of view of a user of watercolors, so it should be easy reading for anyone who has passed through grade school. There is, however, a lot of stuff there. Take your time and read through it. You'll find it quite worth while. For people who have a professional interest in color, Charles Poynton's COLOR FAQ has become a standard reference on the Web. I've also made an old tutorial article on color for technical readers available here . It explains how to calculate the color of an object if you know its spectrum. Copyright © 2005 – 2012 Andrew T. Young Back to the . . .

What Colors Can Be Mixed to Make White Light? | eHow What Colors Can Be Mixed to Make White Light? Photos.com/Photos.com/Getty Images White light used to be the subject of much mystery. It took the curiosity of one man to discover the composition of white light and to understand with greater clarity how it could be manipulated. Today we are capable of projecting and mixing light in many different color combinations with relative ease, using modern technology and a basic knowledge of how white light is formed. Newton's Observations Sir Isaac Newton, one of history's foremost scientists, is the man we have to thank for unlocking the mysteries of white light. Although rainbows in the sky long provided a clue as to the interaction between white light and colored light, Newton helped clarify exactly what sort of interaction that was. His experiments with glass prisms showed that white light could be dispersed to form the colors of the visible spectrum and then rejoined to form white light again. Basic Composition White light is comprised of all of the other colors of light in the visible spectrum, from red to violet. All one would need to make white light is a projection of the three primary colors of light: red, blue and green.

When flashed together on a screen or other surface at the same intensity, their overlapping area of interaction will be as white as a spotlight. Complementary Colors Blending the primary colors in equal proportion works fine for creating white light, but one can also mix white light with just two colors of light, as long as these colors are complementary. An effective guide to use to determine complementary colors is a color wheel. The simplest color wheels display each of the primary colors of light in a circle, as well as colors of light created by combining any two primary colors. If you combine a primary color with the color created by the other two in perfectly equal proportion, then you also get white light. For example, red and green light create yellow light when mixed equally. Yellow light, when mixed with blue light, the remaining primary color, will form white light. This process is known as additive mixing. Practical Applications White light mixing is important for use in television sets and other devices or appliances that use light screens, such as cell phones and computer monitors. The whiteness of a blank word processor document does not reflect the absence of light, but the concentrated presence of it, for example. Color mixing is also important for live stage productions, such as theater plays or musical performances.

Question: Which term describes any two colours which together produce white light?
Answer: Complementary