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Artificial Light
Figure 1-14.-The position of the discharge tube in relation to the reflector

Photography (Basic) - Introduction to photography and other graphic techniques
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Tungsten-Halogen   Lamps Tungsten-halogen lamps have a tungsten filament inside a quartz envelope. This type of lamp does not blacken the inside of the envelope and operates at an almost  constant  brightness  and  color  temperature throughout  its  life.  Tungsten-halogen  lamps  for photography  operate  at  color  temperatures  of  3200  K and 3400 K. Filters can be used to convert them to daylight.  For its size, a tungsten-halogen lamp generally delivers more light than a conventional 3200 K lamp. Tungsten-halogen lights are becoming more popular and  are  rapidly  replacing  regular  tungsten  lights  for general  photographic  use. Fluorescent  Lamps Pictures made on daylight type of color films under fluorescent lights without a filter may be acceptable; however, they usually have a greenish cast. When a tungsten type of color film is used with a fluorescent lamp without a filter, the pictures usually are too blue. Fluorescent light is not generated by heat, as are other  types  of  light.  It  has  special  characteristics different  from  either  daylight  or  tungsten  light. Fluorescent  lights  have  no  true  color  temperature,  but  a value  of  approximate  color  temperature  has  been worked out. Daylight fluorescent lamps: 6500 K Cool, white fluorescent lamps: 4500 K Warm, white fluorescent lamps: 3500 K Electronic  Flash  Lamps Electronic flash is an excellent light source for both outdoor and indoor photography, especially when the predominant  lights  are  fluorescent.  Electronic  flash  uses a discharge tube filled with xenon gas and is supplied with a powerful charge of electricity from a capacitor. The flash is triggered by means of an electrical current that ionizes the gas. The output, or intensity of the flash, is usually given in effective candlepower-seconds and depends on the voltage and size of the capacitor. The design of the reflector on an electronic flash has a direct relationship  on  the  efficiency  of  the  unit. Electronic  flash  resembles  daylight  in  color  quality and  is  excellent  for  exposing  daylight  type  of  color films. The duration of the flash is short, usually 1/500 second or less. With a computerized (automatic) unit used close to the subject, the flash duration can be as Figure 1-13.–A lamp reflector can increase the intensity of light reaching the subject. short as 1/50,000 second. Computerized electronic flash units have a sensor that switches off the flash when the subject (depending on its distance and tone) has received enough  light  for  proper  exposure. Reflectors Two  types  of  reflectors  are  of  importance  in photography. They are the lamp reflector and the plane reflector.  The first type, the lamp reflector, is used with artificial light sources-tungsten, tungsten-halogen, fluorescent, and electronic flash lamps to direct the light. The second type, the plane reflector, is used to redirect light from any kind of light source into shaded areas to soften or lighten shadows. (While it is true that mirrors are also reflectors, reflector is used in photography as a more general term. Mirrors always reflect specular light; and reflectors reflect either specular or diffused light.) LAMP REFLECTORS.  –Light  emitted  by  the filament of a lamp is dispersed in all directions. This is useful when the lamp is for general illumination, such as one suspended from the ceiling to light a room. As a photographer,  however,  you  are  usually  interested  in illuminating only a given area, and it is, therefore, to your advantage to concentrate the light emitted by a lamp onto the area of interest. You can do this by mounting the lamp in a concave reflector that reflects almost all the light onto the area to be photographed (fig. 1-13). Lamp reflectors generally have a satin or matte finish to diffuse the reflected light to prevent hot spots that could result if the reflector surface were highly polished. Reflectors  of  electronic  flash  units  vary  con- siderably in their efficiency and covering power at 1-9







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