background,  you  must  prevent  the  background  from reflecting colored light onto the sides of the subject's face.  This  produces  a  sickly  appearance.  The background tone can be changed by adjusting the amount of light falling upon it. Dark backgrounds with earthen colors, such as brown and dark orange, can be used  for  low-key  portraits.  Intensely  illuminated backgrounds with light pastel colors can be used for high-key  portraits. Your studio should have enough backgrounds to meet the demands of customers. As a minimum, you should have a gray or light blue background for roster photographs  and  white  for  full-length  photographs. Always  stock  extra  white  seamless  paper.  White seamless paper is used mostly for full-length photo- graphs. This paper becomes dirty and is torn rapidly since it is being continually walked on. You can extend the life of the background paper for full-length portraits by laying sheets of acetate (such as clean-up film) on top of the area to be walked on. The acetate does not show up on the film or print. Lights  and  Accessories Almost any type of light can be used for portrait photography. This includes natural light, such as the sun, as well as artificial light, such as electronic flash. The sun, with its different forms of illumination- daylight, skylight, and window light-is the major source of natural illumination for portraits. The sun is used primarily for location portraiture. Most types of artificial light can be used for portrait photography  as  long  as  the  intensity  is  sufficient  to permit  short  exposures.  Short  exposures  are  desired because it is difficult to keep a subject motionless during a long exposure. For color portraits, the color quality of the light source should be the same as that for which the film is balanced. Of all the artificial light sources available, electronic flash is the best light source for portrait  photography  because  of  the  following: It provides a large output of light without the annoying  heat  produced  by  incandescent  lights. The extremely short duration of the flash stops subject  movement. The color temperature of the light is compatible with  daylight. They are as versatile as other light sources. Electronic flash units specifically designed for portraiture   usually have tungsten modeling lamps located near the electronic flashtube. These modeling lamps provide constant, low-intensity illumination on the subject or background. This allows you to see the lighting effect that will be produced when the electronic flash units are fired. BASIC  LIGHTING  UNITS.–Studio   electronic flash units are divided into two broad classifications: those   that   project   a   relatively   narrow   cone   of concentrated, crisp light and those that project a broad area of softer, more diffuse light. Spotlight.–A spotlight projects a narrow, highly concentrated, crisp beam of light, produced by an undiffused clear flashtube. A Fresnel lens or a small reflector with a mirror finish is used to direct and focus the light. The light produced by a spotlight is very much like direct sunlight on a clear day. The light rays are nearly parallel and are not diffused. The shadows cast by a spotlight are hard with sharply defined edges that add crispness. A spotlight is usually used to highlight or stress a feature of the subject or as a hair light or background  light. Floodlight. –A floodlight produces a broad area of partially diffused, soft light, very much like sunlight on an overcast day. A frosted globe is used over the flashtube, so the light produced is initially diffused. The light is further diffused by the reflector that causes the light rays to cross and interfere with each other. The rays, projected from the front of the flashtube, however, are not as diffused and have a crisper quality. The light, produced by an electronic flash floodlight, has a crisp quality at the center and a softer quality toward the edge. When you want to use just the softer part of the light, allow only the outer part of the light beam to fall on the subject. This technique is called feathering  the light. When you want the entire beam of light to be diffused and very soft, use a diffusing screen over the light source. There is also a type of light unit known as a capped light. This type of unit has an opaque metal cap placed in front of the flashtube to block specular light from reaching the subject. All light projected by a capped unit is diffused. A floodlight is usually used as the main (modeling, or key) light in portraits, especially where a soft effect is desired. It is also used as a fill light because a fill light is  always  diffused. ACCESSORIES.–Many  accessories  are  available for use with studio lighting units. Accessories are 7-3