Color Models
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`Color Models
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`The search for a comprehension of exactly what color is and how it functions has been going on for hundreds of years.
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`Numerous models and systems have been developed, and the following is an attempt to summarize some of the major leaps
`that have been made to bring our understanding to its current level.
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`The first known studies of color were done in ancient Greece by Aristotle, who theorized that color existed in the form of
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`rays sent down from the heavens by God. His theory was not disputed until the Renaissance when more sophisticated color
`systems were developed by Aguilonius and Sigfrid Forsius. Aguilonius's system was the first attempt at defining all colors
`and was based on his observations of the changing color of the sky from dawn to dusk, (see below).
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`In 1660, Sir Issac Newton developed a more logical color order based on his scientific observation from experiments. Using
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`a prism, Newton acknowledged that white light could be broken down into the colors of the rainbow, and as such had a clear,
`set order. Newton's work in optics led to his creation of the color wheel.
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`The next big jump in color theory did not come until the early 1800's, when Johanes Wolfgang Goethe challenged
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`Newton's ideas and created his own color system. Newton's and Geothe's approaches were very different. Newton's studies
`in color were scientifically based, while Goethe's interest was more in the psycological effects of color. He wished to
`investigate whether rules could be found to govern the artistic use of color. Originally he planned on creating an improved
`color wheel, but later Goethe found his ideas were best expressed within an equilateral triangle. (see below) Goethe's
`theories and his triangle will be explored further in the Goethe's Triangle section of this page.
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`Also around this time Phillip Otto Runge developed a three dimensional color model in
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`the form of a sphere. His theory was revolutionary at the time, and it attempted to arrange
`colors based on hue (red,cyan,orange,etc..), whiteness, and blackness. You can see from
`the two top views in the example, that the pure hues on the outside of the sphere lighten
`and darken as they reach the two poles. Horizontal and vertical cross-sections are shown
`below them.
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`In 1872 a Scottish physicist, Sir James Clerk Maxwell,
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`developed a chart in the form of an equilateral triangle from
`his studies of the electromagnetic theory of light. His triangle is very similar to Goethe's, both
`are equilateral and both choose three primaries which are combined to produce the inner
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`https://web.archive.org/web/20000124152013/http://www.cs.brown.edu/courses/cs092/VA10/HTML/ColorModels.html
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`Legend3D, Inc. Ex. 2008-0001
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`Color Models
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`colors. Maxwell, however, believed that he could produce all the known colors within his
`triangle, and he choose red, green, and blue as primaries.
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`In 1915, Albert H. Munsell, an American art teacher, used the work of Runge as a basis for
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`the development of his own 3D color space. This space is based on pigment, not light. He
`begins with Runge's sphere, but he works from two observations that he has made as a painter.
`The first is that pure hues vary in their degree of lightness, and therefore all the pure hues (red,
`yellow, green, blue, violet) should not be on the same horizontal plane. The second
`observation is that some colors(red) are more vivid than others(green), and therefore,they
`should be further away from the axis. These observations all pointed Munsell toward a color
`space whose shape was very irregular and asymmetric, as shown below. Munsell's color solid
`has remained very useful, and is used by paint manufacturers, artists and designers.
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`In 1931, an attempt was made to establish a world standard for the measurement of color by the Commission Internationale
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`de l'Eclairage (CIE). They generated a version of Maxwell's triangle, choosing a particular red, green, and blue from which
`to generate all the colors. The result became known as the CIE chromaticity chart, the updated version of which is used to
`measure and quantify the light produced by computer phospor guns today.
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`With the advent of the computer age, many attempts have been made to create an ideal color space model based on
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`the red, green, and blue primaries of the computer screen. The simplest model is the RGB Cube, with corners of black, the
`three primaries(red, green, blue), the three secondary mixes(cyan, magenta, yellow), and white. Although this creates an
`accurate representation of the colors that can be produced on a computer or television screen, it is only intuitive to someone
`already familiar with RGB mixing. Other models, that were created to describe a color space that would be more natural to
`the user, include HSV space(hue, saturation, value) and HSL space(hue, lightness, saturation).
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`For this site, we have created a model of the HSL Double Cone and of the RGB Cube. We choose the HSL Double Cone
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`because we felt it was the most easily understood, and it corresponded in many ways to pigment-based models. We choose
`to include the RGB Cube model to allow you to become more familiar with mixing red, green, and blue color values, and to
`emphasize the differences between pigment-based, artistic models, and electronic, science-based models. On the next page
`you will find an example of the color chooser, containing both HSL and RGB spaces, that you can explore. You will also be
`using this to choose colors in the upcoming exercises.
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`able to flip between these two spaces on the chooser by clicking the "Change Color Picker" button.
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`Below, you will see a static version of the color chooser, displaying both the RGB and the HSL color spaces. You will be
`In the RGB color space, you may use the red, green, and blue sliders to change your color. A rectangle containing you
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`current color selection is shown on the left. The amounts of red, green , and blue (on a scale from 0 to 255) are indicated in
`the text box beside the slider, and a visual representation of the amounts are shown on the sliders themselves. Experiment
`with mixing different amounts of red, green, and blue to create different colors and notice how different it is from
`pigment-based mixing.
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`https://web.archive.org/web/20000124152013/http://www.cs.brown.edu/courses/cs092/VA10/HTML/ColorModels.html
`
`Legend3D, Inc. Ex. 2008-0002
`PRIME FOCUS V. LEGEND3D
`IPR2016-01243
`
`

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`Color Models
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`3 of 3
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`In the HSL color space a horizontal slice of the shape is shown on the left and a three-dimensional representation of the
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`shape is shown on the right. As in the RGB chooser, a rectangle containing your current color selection is shown on the left.
`The color can be chosen from the 'slice' by clicking on the black out-lined circle and moving it around in the space. Also,
`different slices can be choosen from the shape by clicking and dragging the slice up and down. By manipulating these, you
`can navigate through the shape to find your desired color.
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`Note: You may need to resize your browser window.
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`Electronic Color
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`Color Chooser applet
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`https://web.archive.org/web/20000124152013/http://www.cs.brown.edu/courses/cs092/VA10/HTML/ColorModels.html
`
`Legend3D, Inc. Ex. 2008-0003
`PRIME FOCUS V. LEGEND3D
`IPR2016-01243