Light source is made up of 3 basic components, PHOTONS Red Green Blue. Light is a radiant energy that moves in waves. Each color of light has a different wavelenght (ferquency). As light radiates from it's source and strikes an object, there are 3 things that can happen to the lightwaves. First they can bounce off of the object; this is reflected. They can also be absorbed by the object, like a plain dull black object, if you put such an object for a given time in the sun and try to pick it up, hot stuff. The lightwave can also go right through the object, technically speaking called transmitted, like glass, the light strikes the glass and goes through it. Depending on the composition of the object, all of the light striking it may be reflected, absorbed or transmitted. Realistically, it will be some combination of the 3. Pure or white light contains all of the colors of the visible spectrum. When white light strikes a banana, the blue components of the light is absorbed and the red and green components are reflected. These reflected colors are then received by the eye. The banana appears yellow because the red and green reflected light combines to create yellow. If an object absorbs all of the red green blue photons, it appears black. Conversely, if an object reflects all the photons, it appears white. Color is made up of light components (photons)that, when combined in varying percentages, create separate and distinct colrs. You also learned this in elementary school when the teacher had you take the blue poster paint and mix it with the yellow paint to make green. Mixing pigments on a palette is simple. Mixing colors on a computer is different. The rule that that govern the mixing of computer colors change, depending on the color model being used. There are many color models available. They provide different ways to view and manipulate an image. Regardless of the one selected, they fall into one of two basic categories : Additif or Substractif color model. Additif color, also known as RGB, is the system used by color monitors, scanners photography and the human eye. Substractive color, also known as CMYK, is used in four-color publishing and printing. This model is said to use the additif process because are produced by adding one or more colors to produce additional ones. RGB involves transmitted light as the source of the color. In the additive model, color is created by adding different amounts of red, gree and blue light. Pure white light is composed of equal amounts of red, green and blue. For the record, RGB colors are reffered to as the additive primary colors, so called when they are added (combined), they can produce all of the other colors in the visible spectrum. The substractive model is so named because colors are substracted from white light to produce other colors. This model uses the scondary colors, Cyan, Magenta and Yellow. You already saw that this is called the CMYK model. Because combining eqaul amounts of CMY only produce black, in theory, because it also depends on the object's material the colors are mixed on. When Printed, they produce something closer to swamp brown mud than black. So, in order to create a vivid picture, black is added to compensate for the inability of the colors CMY to produce a real black. In case you were wondering, K is used as designator for black since letter B already designate Blue. CMYK is a printers model, based on ink and dyes. It is the basis for almost all Conventional color photography and commercial color printing. CMY dyes and inks simply transmit light better and are more chemically stable than Red Green Blue inks. While defining colors as either numbers of shades in the RGB or percentages of tint in the CMYK is accurate, it is not practical. Givven that we cannot assign names to the millions of shades of colors that are possible, there needs to be a workable solution. The use of color-matching systems like the Pantone° spot color provide a solution. The designer and the printer have a book of print samples. The designer wants to use red in a 2-color publication. He spcifies that the second color is to be Pantone red 032CV. The printer who gets the job looks up the formula in the Pantone book for the percentages of MCY to mix togheter and prints the first sample. He then compares the output with his book of print samples, called a swatch book. The terms Hue, Saturation and Brightness (Luminosity) are used throughout almost all photo editing programs. Hue describes the individual colors, for example a blue object can be said have a blue hue or tint. Saturation is technically the purity of the color. In pratical terms it is the balance between neutral grey and the color. Grey being desaturated. If an image has no saturation, it looks like a greyscale image. If the saturation is 100%, it may look unatural, since the midtones, which the grey components emphasizes, are lost. Brightness is the amount of light reflecting from an object or how dark or light the image is. It may come as a surprise to you, but there are a lot more colors in the real world than photografic films or printing presses can recreate. The technical term for this range of color is Gamut. There are many gamuts for monitors, scanners, photografic films and printing presses. Each gamut represents the range of colors that can actually be displayed, captured or reproduced by the appropriate device or process. The widest gamut is the human eye, which can see billions of colors. Further down in this chain is the color monitor, which can display 16 millions of colors. Photographic film can only capture 10.000 to 15.000 colors and a high-quality 4-color printing process can reproduce from 5.000 to 6.000. We wont even discuss the limitations of color ink on newsprint.