// a light group makes certain light sources only
// influencing certain objects
light_group {
  light_source {          // light sourc(es) of this group
    <100, 100, 100>
    color rgb y
  }
  sphere {                // objects illuminated by those light sources
    <0, -1, 0>,0.5
    pigment { color White }
  }
  //global_lights         // add this to make all global lights
                          // also illuminating this light group
}