The basic area lighting effect washes the whole stage area in a regular glow, letting the actors move freely through the space. Though seemingly uniform, the space is made up of a number of slightly overlapping pools of light, usually given five lights each. These lights are an overhead, two key lights and two fill lights, though some productions use more or less depending on the shape of the stage. The key lights give off a brighter light than the fill, giving the lighting a subtle variance.
To prevent the actors looking flat or washed out, the key and fill lights come in two colors. One key and one fill gives off colder, more bluish light, and the other two (usually along with the overhead light) give off a warmer, more orange color. Though not specifically visible onstage, the color differences give the actors face more depth.
Light changes often accompany time changes or scenery changes in the play. Since the area lighting already contains two colors of lights, changing the balance between them gives off different effects. More blue light might indicate a night scene, or a winter vista. More orange light easily signifies a midday sun, or a lighter mood.
Performances occasionally call for background scenery or objects to change quickly, or for setups outside the budget or scope of the production. In these situations, lights can create shapes and designs using special equipment. Metal or glass stencils, called gobos, slide in front of certain lighting instruments and create the stenciled shape on the stage. Gobos allow for radical scene and mood changes using only a single light. Projected shapes can be as simple as the outline of a tree, or as complex as a full color photograph.
To draw the audience's attention to certain areas, the most common and recognizable technique is spotlighting: training a powerful beam directly on an important stage element. Though it may look like only one light, two or even three lights usually make up the effect, each originating from a different direction to remove the harsh shadows the light would otherwise cast. Trained operators move the spotlights manually to track actors across the stage.