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Characteristics of Light
Color Relationships

Photography (Basic) - Introduction to photography and other graphic techniques
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Figure 1-4.–Light emitted from a source. Once light is produced (emitted), it is no longer dependent on its source, and only its speed is affected by the many mediums through which it can travel. Another example of the independence of light is that when light travels from air into a denser but transparent medium, such as glass, its speed is reduced. But when it leaves the glass, it returns to its original speed. This changing speed is important in refraction, a behavior of light that allows lenses to form images. Unless light is reflected or focused, it travels or radiates in all directions from the source. As light travels from the source, its energy of light spreads out. The greater the distance it travels, the more it spreads out (fig. 1-4). Therefore, the amount of light reaching a given area at a given distance is less than that reaching the same area closer to the source. In other words, the intensity of illumination on a surface varies when the distance between the light source and the surface, or subject,   is  changed.  This  becomes  important  when exposing  film  with  artificial  light. COLOR OF LIGHT Look at a bright, red apple on a dark, green tree. It is hard to believe that color is not an inherent property of these objects; in fact color is not even inherent to light. What you are seeing is a visual perception stimulated by light. The apple and tree are only visible because they reflect light from the sun, and the apple appears red and the tree appears green because they reflect certain wavelengths of light more than others. In this case, these particular wavelengths are seen by the human eye as red and green. When we see a color, we are simply seeing light  of  a  particular  wavelength. When a beam of light has a relatively even mixture of light of all visible wavelengths, it appears as white light. When this beam of white light is passed through a prism, its different wavelengths are spread apart and form a visible spectrum. This visible spectrum is seen as a band of colors, such as violet, blue, blue-green, green, yellow, and red (fig. 1-5). COLOR TEMPERATURE White light is made up of nearly equal intensities of all wavelengths within the visible spectrum. By passing white light through a prism, scientists have found that light  sources  have  many  qualities.  They  are  as  follows: Different wavelengths are present in the sources of radiant energy. The  frequency  and  color  of  wavelengths  vary. C302.8 Figure 1-5.–Refraction of light by a prism. 1-3







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