![]() ![]() White light combines all of the colors in the 'visible spectrum', which is the range of colors we can see.Įach color in the visible spectrum represents electromagnetic waves of differing lengths. The Earth's natural source of light is the sun which provides 'white' light. In conclusion, any color has to be specified by three parameters, hue, saturation (or chroma) and luminance, or any other three equivalent parameters, as will be described in more detail later.The color of a cloud depends primarily upon the color of the light it receives. In these two examples, the difference between the two red samples is its lightness or luminance. In another example, if a pure red color is mixed with black, its appearance is different. If one of them is strongly illuminated and the other is almost in darkness, the two colors look quite different. Let us consider two identical samples of a spectrally pure red color. Therefore, the relative amounts of a mixture of white and a spectrally pure color determine the color saturation, or chroma.Īgain, combinations of spectrally pure colors and white cannot produce all possible colors in nature. The degree of saturation is called the chroma. All of these colors obtained by mixing a spectrally pure color with white are said to have the same hue but different saturation. In this manner, a mixture of red and white produces a pink color that goes from pure red (100% saturated) to white (0% saturated), depending on the relative amounts of red and white. ![]() Not all colors in nature are spectrally pure, since they can be mixed with white. Thus, we say that the ear is an analyzer.įigure 1.2 The visible spectrum with Hydrogen spectral lines as a reference. In contrast, when the ear listens to an orchestra, the individual instruments producing the sound can be identified. For this reason we say that the eye is a synthesizer device. Only with an instrument called a spectroscope can two or more components used to produce a color be identified by the eye. Instead, it means that it has the same color as the single wavelength light beam matching its color. In this book, when we refer to a spectrally pure light beam it does not mean it is formed by a single wavelength beam, as in traditional physical or interferometry books. ![]() However, the same color can be produced with a combination of two light beams, one being red with a wavelength of 700 nm, and another being yellow with a wavelength of 580 nm, with no orange component. For example, an orange color is associated with a wavelength of 600 nm. A spectrally pure or monochromatic color can be produced by a single wavelength. Different spectrally pure colors are said to have a different hue. They are related to the wavelength, as illustrated in Fig. The spectrum of colors produced by a prism is referred to as spectrally pure or monochromatic. The sensation of color is produced by the physical stimulation of light detectors, called cones, in the human retina. However, the scientific study of color only goes back to Newton when he performed his classical experiment with a prism. Spectral regionįor many centuries, humans have been quite interested in color. Table 1.1 Ultraviolet, visible, and infrared regions of the electromagnetic spectrum. ![]()
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