Old Color Spaces

From Dead Media Archive

Jump to: navigation, search

The color space is a graphic and numerical representation of colors and their relationship to one another. The purpose of the chart is to standardize and quantify what is frequently a subjective experience. Detailed color standards are commonly used in product development and design arenas; standards become outdated rapidly as new products are developed. Color spaces and standards assist in "express[ing] a given color [of an object] accurately, describ[ing] that color to another person, and hav[ing] that person correctly reproduce the color we perceive" (Konica Minolta 1).

Contents

COLOR BASICS

HSB or The “Three Dimensions” of Color

(Gerritsen/Microsoft)

HSB stands for Hue-Saturation-Brightness and is a color model dependent upon a color wheel and the percentage of the amount of white present in a designated hue.

Hue

Hue is color itself as it is placed on a color wheel where each color has a percentage. Red is at 0o, yellow is 60o, green is 120o, etc. This percentage coincides with the frequency of light waves reflected of any given object for that color in respects to the color spectrum. Each tone group (red, green, etc) can than be affected by saturation and brightness in order to vary its shade and intensity.

Saturation

Often given as a percentage, saturation is the intensity of color for a specific hue. It can also be described as how different a color is from grey at any lightness. Colors that are more vivid are considered more saturated while colors that are more muddled and closer to grey are less saturated.


Brightness

Brightness of an object is a difficult thing to measure because it is perceived. While looking at a computer screen in a dark room, colors appear brighter than if the room was well lit. But generally, brightness measures the luminosity of a color.


Additive Color Mixing

Additive Color Mixing

Additive color systems, such as RGB, mix the three primary colors together as a way to produce more colors. The secondary colors of cyan, magenta and yellow are results of mixing two of the three primary colors together. White is created when all three of the primary colors are mixed together proportionately. The additive color theory was discovered by James Clerk Maxwell in conjunction with a photographer, Thomas Sutton. Maxwell had Sutton photograph a piece of ribbon three times, each with a different filter over the lens (one red, one blue, one green). He then projected each image from a different projector onto a common screen. The three separate images then formed a complete one with full coloring.


Subtractive Color Mixing

Subtractive Color Mixing

Louis Ducos du Hauron was responsible for the discovery of the subtractive color theory. Subtractive color mixing removes some colors from white light while allowing others to pass. The CYMK model is an example of a subtractive color space. It uses cyan, yellow, magenta and black to create colors. When white light is passed through one of these secondary and subtractive color filters, two of the primary colors which form the secondary color are transmitted through the filter and the third one is absorbed. When equal amounts of all the subtractive colors overlap, all primary colors are blocked and black is produced. Subtractive color mixing is more advantageous than additive because of its ability to create more colors. When the proportion of overlapping filters is changed, almost any color can be created. Viewing equipment for subtractive coloring is also cheaper (Kirsch 28-35).



The Munsell System

Brief Bio

Albert H. Munsell lived from 1858-1918 in Boston, MA. He attended Massachusetts Normal Art School (now Massachusetts College of Art), where he later became a member of the faculty. Although the color system he began developing is widely used by scientists and artists alike, Munsell did not consider himself a scientist. He was a trained painter frustrated with the lack of color descriptions and a systematic color scheme. Munsell began developing his color system when he was a teaching aid for color composition students. As the system became more advanced, Munsell was able to share his color distinction system with well-respected scientists and engineers around Boston. He published “A Color Notation” in 1905, which described his system so far. Munsell wanted his system to be used in a broad sense, rather than only in science and art. His goal was to use it to teach concepts of color to primary school students. Unfortunately, Munsell’s health began to decline in 1914 and he passed away in Boston in 1918 at the age of 60. After his death, Dorothy Nickerson (who first worked as secretary to Munsell’s son) worked to adapt the Munsell Color System. The charts could finally be put to widespread use 30 years after Munsell died. (Landa)

The System

The Munsell system is now the most widely used and accepted color system. All other color systems that arise are compared to the Munsell System, which has come to be known as the standard color system. The system builds on the guiding principle of equal visual perception. This is the idea that we all perceive colors differently, but the system accounts for any small discrepancies based on comparison to a grayscale, assuming the eyes seek the balance of grayscale (Evans). The system is able to describe all possible colors in terms of three coordinates:

1. Munsell Hue: the quality of a color described at red, yellow, blue and so on

2. Munsell Value: the place where a color falls in terms of lightness when compared to a scale of grays from white to black

3. Munsell Chroma: the degree of difference between a color and a gray of the same value.

The Munsell Book of Color is a compilation of color samples, usually arranged in pages of a book, or on a color “tree.” The Munsell Value is vertical in a display and the Munsell Chroma is horizontal. The scale of grays can be considered the “trunk” of the color tree, going from white on top to black on the bottom.


Munsell Tree
,
Munsell Book
,
Munsell Tree

Each sample has a Munsell Notation, which tells us its position on the tree. The notation consists of three symbols that represent Munsell Hue, Munsell Value, and Munsell Chroma.

An example of Munsell Notation

The Munsell System is the most accepted color system because colors are not limited to the samples shown, whereas other color systems are. Any color that can be conceived will fit into the Munsell System. (Billmeyer and Saltzman)


Natural Color System & Color Opponency

Color Opponency

Color Opponency

The Natural Color System is based upon the color opponent theory. The color opponent theory focuses on the uniqueness of four hues and their inability to be described simultaneously. R.W.G. Hunt describes color opponency: “The hues red, yellow, green and blue are said to be unique because they cannot be described in terms of any combinations of other color names. Thus, for instance, although orange can be described as a yellowish red or reddish yellow, red cannot be described as a yellowish blue or a bluish yellow. In fact the four unique hues comprise two pairs, red and green, and yellow and blue; the colors in each of these pairs are opponent, in the sense that they cannot both be perceived simultaneously as component parts of any one color. That is, it is impossible to have a reddish green, or a greenish red, or a yellowish blue, or a bluish yellow. But yellowish reds… greenish yellows… bluish reds are all possible (140-141).” Black and white are also used in the color opponent theory to determine variations of light and dark.


NCS

NCS Notation
The Natural Color System was developed by the Scandinavian Color Institute. Using NCS a color is measured based upon its percentage in comparison to a color opponent pair. A color therefore that is purely red and has no green is at 100% red. Darkness of a color and saturation are also taken into consideration when measuring the color being presented. A sample notation taken from the NCS website is shown to the right. The letter S in front simply means that the NCS is responsible for measuring a specific color.
NCS Color Wheel
The nuance describes the “degree of resemblance to whiteness and blackness.” Chromaticness puts the color at a grey. The ten percent blackness thus mean that there is 40 percent whiteness in the color. The Y90R describes the hue of the color. This example shows a yellowish color with 90 percent red. The ten percent yellow is than inferred (Hunt 141-143/The NCS System).












The CIE Color Spaces

CIE Yxy

In 1931, the Commission Internationale de l'Eclairage (CIE) devised the Yxy color space, and in 1976 created the L*a*b* to "provide more uniform color differences in relation to visual differences" (Konica Minolta 14). The CIE systems are used in conjunction with a colorimeter.

CIE Yxy

The Yxy color space is based on the three-component theory of color vision, which places red, green, and blue as the primary color receptors in the eye. All other colors are combinations of those three primary colors. Because lightness and darkness cannot be taken into consideration with RGB values, a third variable, Y lightness, makes up the Yxy system. Moving towards the center of the graph increases lightness; moving toward the edges increases chromaticity (another word for saturation). (Konica Minolta 16)

CIE L*a*b*

CIE Lab showing the variables
The CIE L*a*b* color space was invented because the original Yxy color space had a problem: "equal distances on the x, y chromaticity diagram did not correspond to equal perceived color differences" (Konica Minolta 18). L* indicates lightness and a* and b* are the hue coordinates. +a* is the red direction, -a is the green, +b is the yellow, and -b is the blue direction. In the center lies achromatism (grayness). (Konica Minolta 18)
CIE Lab sphere

Colorimeters

A colorimeter is the device that measures the color coordinates of an object. Colorimeters can detect even minute differences in color and are commonly used in production so that the color of the product can be standardized. Companies determine how much tolerance--how much color variation is acceptable--in a product. The colorimeter is very fast, producing coordinates in less than a minute, and can be utilized on assembly lines. It features a built in light source so that the light remains uniform, data memory and display, and constant viewing and illumination angles. It eliminates area effect (when an object appears to be a different color due to size, paint chips vs. a painted wall for example) and contrast effect (when an object appears to be a different color when viewed with other objects). Colorimeters measure colors with three photocells calibrated to match the CIE 1931 standards, so that the observer is constant for all measurements. Essentially, with the colorimeter, almost all of the variables that make an object appear to be a different color--observer differences, light source differences, and angle differences--are eliminated. There are other types of colorimeters for the purpose of measuring objects of varying texture, including spectroradiometers, which measure emitted, transmitted, and reflected light; spectrophotometers, which measure reflected and transmitted light; glossmeters, which measure gloss; and goniospectrophotometers, which measure reflected color as function of angle. (Konica Minolta 26).

Colorimeter

One problem with the standard colorimeter is that it cannot detect metamerism, a phenomenon in which two objects appear to be the same color under certain illuminants but under different circumstances are revealed to be different colors--for example, picking out two black socks in the morning and then realizing under fluorescent light that one is actually navy. Since the colorimeter's light source mimics only daylight, a spectrophotometer is required to make sure that two objects will look the same color under different types of light, or "illuminants" (Kinoca Minolta 42).

Common Color Spaces

A color space is a three-dimensional concept, in that it considers hue, value, and chroma. The most commonly used color spaces are hue based. These include RGB (red, green, blue), RYB (red, yellow, blue), and CMY (cyan, magenta, yellow).

The left circle was developed by Johannes Itten; it is a circle of the primary colors. The primary colors are still taught in art schools and classes today using this circle. The circle on the right is used today in computer graphics. The additive primary colors of this circle (red, green, and blue) produce white light when added together on a computer. The subtractive primaries (cyan, magenta, and yellow) are the complementary colors on the circle. When they’re added on the computer, they produce black, or the absence of color. When comparing the two circles, we can see that they contradict each other. The circle on the left suggests that red and green are complementary to each other, but in the circle on the right, they are both primary. This example shows that color can be subjective, “the perception of color is inexact, culturally influenced, and personal” (Evans).

Obsolete Color Space: RG & Early Film

Both Kinemacolor in England and Technicolor used red and green primary colors to produce images in film until blue was introduced as an easier means to produce a fuller image. Early motion pictures in England used this two -color process. Edwin Slosson describes the Kinemacolor system as “red and green being taken and projected alternately by means of a rotating disk of tinted filters. Because an image on the retina persists for about a sixteenth of a second before it fades away, each color fused with the succeeding one, except when movement was too fast (62).”

Technicolor exposes two strips of black and white film to two different filters simultaneously. One was behind a red filter and the other a green. It had much the same problems as Kinemacolor because of the issue of speed. But since this was an additive method of color mixing, a subtractive method was tried.

A successor the Gaumont Process used glass plates in an attempt to rectify the RG system. It “employed three pictures taken in the three primary colors by three lenses on the same film and projected through three objectives.” Dots, ruled lines or starch grains were used on the glass plates in the three colors. However, when enlarged, picture quality is diminished so although color is improved overall picture is not.


Bibliography

Billmeyer, Fred W., and Max Saltzman. Principles of Color Technology. Second Edition ed. New York: Wiley-Interscience, 1981. 25-66.

Evans, Brian. "Foundations of a Visual Music." Computer Music Journal 29 (2005): 17-18.

Gerritsen, Franz. Evolution in Color. Grand Rapids: Schiffer, Limited, 1988.

Hirsch, Robert. Exploring Colour Photography: A Complete Guide. London: Laurence King, 2004.

Hunt, R. W., and R. W. Hunt. Measuring Colour : A Photographer's Paradise. New York: Fountain P, Limited, 1996.

Kindem, Gorham. "The Demise of Kinemacolor: Technological, Legal, Economic, and Aesthetic Problems in Early Color Cinema History." Cinema Journal 20 (1981): 3-14.

Konica Minolta Sensing, Inc. "Precise Color Communication." Osaka, Japan: Konica Minolta, 1998.

Landa, Edward R. "Albert H. Munsell: A Sense of Color at the Interface of Art and Science." Soil Science 169 (2004): 83-89.

Microsoft Computer Dictionary. New York: Microsoft P, 2002.

"The NCS System." The Natural Color System. Scandinavian Color Institute. <http://www.ncscolour.com/webbizz/mainpage/main.asp.>

Slosson, Edwin E. "How New Color Movie Camera Works." The Science News-letter 14 (1928): 61-62.

Personal tools