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Color Models
   

 


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There are three basic ways of describing color systems, or models, and these are described in reasonably concise form below - giving you I hope some insight into the different versions if you have not met them before, or just need a "refresher".


The Additive Model -

The Additive Color ModelThe Additive color model (see also color facts) is built on three colors called the additive primaries. The additive primary colors are red (R), green (G), and blue (B). By mixing these colors in different percentages, any other color can be created. When blue and green are mixed, the resulting color is cyan. When blue and red are mixed, the resulting color is magenta. If all three primary colors are mixed together, the resulting color is white.

The Additive color model is best depicted in computer monitors and television screens. Both are composed of tiny red, green, and blue illuminating dots.

Overlapping circles of blue, red, and green light create white at the center and three secondary colors: cyan, magenta, and yellow.

The Additive color model can be illustrated further by looking at your image software's Color Picker. Double-click the Color Swatch or any color in the Color Palette to open the Color Picker. By changing the RGB values in the Color Picker, you can immediately see the resulting color. Set blue (B) and green (G) to 100% and the color is cyan. Set blue (B) and red (R) to 100% and the color is magenta. Notice that if all RGB values are the same, the resulting color is a shade of gray.

The Additive color model is sometimes known as the RGB color model or the Emittive color model.


The Subtractive Model -
The Subtractive Color Model
The Subtractive color model is built on the subtractive primary colors. The subtractive primary colors are cyan, magenta, and yellow. The colors created by the mixing equal amounts of subtractive primary colors create the additive primary colors.The opposite is also true; the mixing of equal amounts of additive primary colors creates the subtractive primary colors.

Printers use combinations of the subtractive primaries to produce practically every color in the spectrum. Notice when cyan, magenta, and yellow are combined, black results.

The Subtractive color model is implemented in the printing industry. Cyan, magenta, and yellow are three of the four ink colors used in four-color, or process, printing. Printers combine these three colors to produce virtually every color in the spectrum. A fourth color, black, is usually added because ink impurities make it difficult to create a true black. (When pure cyan, yellow, and magenta colors are mixed together, black is the resulting color.)

The Subtractive color model is sometimes known as the CMYK model or the Reflective color model.


The HSL Color Model -

The Hue, Saturation, and Lightness (HSL) color model defines a color based on its hue (color), saturation (purity of the color), and lightness (brightness).

Hue -

Hue is what we usually define as the color of an object. The hue of the sky is blue, the hue of a banana is yellow, and the hue of an apple is red. The color wheel is a useful tool in understanding hue and the numeric values assigned to hues. The lightness axis adds a third dimension to a color wheel, which produces the HSL color model.

The hue of a color is assigned a number from 0 to 360. Red is defined at the 0 point, blue is 120, cyan is 180, green is 240, and so on. Change the hue (H) values in your image software's Color Picker to see the hue change. Also, look at a Hue Shift slider in an image software Hue Map dialog box for another way to change the hue of an image.

The HSL Color Model
Saturation -

The saturation of a color describes the purity of the color. The range of saturation is defined in value percentages from 100% (full color intensity) to 0% (no color intensity). A black-and-white photograph has a color saturation value of 0%. Look at a Saturation Shift slider in a Hue Map dialog box to see how changes in saturation affect an image.

Lightness -

Lightness refers to the amount of white or black in a color and is defined in percentages from 100% (totally white) to 0% (totally black). Fifty percent lightness is the pure hue. Look at a Lightness Shift slider in a Hue Map dialog box to see how changes in lightness affect an image.


The above gives a only brief outline of the color models but if you are particularly interested in this subject then there is much good reading on the matter to be found in many books and on the web.


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