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In addition to using Hue, Saturation and Brightness (HSB);

In addition to using Hue, Saturation and Brightness (HSB); Many (but not all) colors can be described in terms of the relative intensities of a light mixture of a certain wavelength red, wavelength green and wavelength blue lights 650-nm red 530-nm green 460-nm blue

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In addition to using Hue, Saturation and Brightness (HSB);

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  1. In addition to using Hue, Saturation and Brightness (HSB); Many (but not all) colors can be described in terms of the relative intensities of a light mixture of a certain wavelength red, wavelength green and wavelength blue lights 650-nm red 530-nm green 460-nm blue These are called the additive primaries The mixing of the additive primaries is called additive mixing Additive mixing is usually done by mixing primary color lights with different intensities but there are other ways to be discussed later Demonstrate with Physics 2000 Red, greenandblue(RGB): RGB is another way to use 3 numbers to specify a color instead of using an intensity-distribution curve or HSB http://www.colorado.edu/physics/2000/tv/colortv.html yellow 650-nm red 530-nm green magenta cyan 460-nm blue

  2. Definition of complementary color (for additive mixtures): The complement of a color is a second color. When the second color is additively mixed to the first, the result is white. Blue & yellow are complementary B + Y = W. Green & magenta are complementary G + M = W Cyan and red are complementary C + R = W Magenta is not a wavelength color— it is not in the rainbow There is at most one wavelength complementary color for each wavelength color (Fig 9.9) yellow red green magenta cyan blue Complementary additive colors white

  3. Additive mixing of colored light primaries Blue added to green = cyan. Green added to red = yellow. Red added to blue = magenta.

  4. Complementary colored lights(additive mixing) Blue (primary) and yellow. Green (primary) and magenta. Red (primary) and cyan.

  5. Partitive mixing is another kind of additive color mixing but not achieved by superimposing colored lights! Instead, it works by putting small patches of colors next to each other. From a distance these colors mix just as though they were colored lights superimposed on each other Examples: Seurat pointillism Color TV and computer screens (Physics 2000) Photoshop example What is partitive mixing?

  6. Partitivemixing • http://www.learner.org/teacherslab/science/light/index.html • Read the introduction and click on the “Light in Color” tab. Proceed to work the activity listed below. • Made from dots • Go through and write down at least 5 different color combinations from the program.

  7. Cyan filter subtracts red Yellow filter subtracts blue A colored filter subtracts colors by absorption. = Incident white light Only green gets through

  8. = Magenta filter subtracts green Cyan filter subtracts red A colored filter subtracts certain colors by absorption and transmits the rest Incident white light Only blue gets through

  9. Magenta filter subtracts green Yellow filter subtracts blue A colored filter subtracts colors by absorption. = Incident white light Only red gets through

  10. Rules for combining the subtractive primaries, cyan, yellow and magenta: White light passed through a cyan filter plus a magenta filter appears blue White light passed through a yellow filter plus a magenta filter appears red White light passed through a yellow filter plus a cyan filter appears green Why? What is the effect of combining (sandwiching) different colored filters together? cyan yellow magenta

  11. Colored surfaces subtract certain colors by absorbing them, while reflecting others White in White in Green out Magenta out Magenta surface absorbs (subtracts) green. Green surface absorbs (subtracts) red and blue (magenta).

  12. Green light on a magenta surface appears colorless because green is absorbed Magenta light on a green surface appears colorless because magenta is absorbed Magenta in Green in No color No color Magenta surface absorbs (subtracts) green. Green surface absorbs (subtracts) red and blue (magenta).

  13. Halftone • Left: Halftone dots. • Right: How the human eye would see this sort of arrangement from a sufficient distance or when they are small. • Resolution: measured in lines per inch(lpi) or dots per inch (dpi); for example, Laser Printer (600dpi)

  14. Color halftoning Printer's ink Paper beneath Three examples of color halftoning with CMYK separations. From left to right: The cyan separation, the magenta separation, the yellow separation, the black separation, the combined halftone pattern and finally how the human eye would observe the combined halftone pattern from a sufficient distance.

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