Stage lighting has several functions, although to allow for artistic effect, no hard and fast rules can ever be applied. The functions of lighting include the following:

Illumination: The simple ability to see what is occurring on stage. Any lighting design will be ineffective if the viewers cannot see the characters; unless this is the explicit intent.

Focus: Directing the audience's attention to an area of the stage or distracting them from another.

Mood: Setting the tone of a scene. Harsh red light has a totally different effect than soft blue light.

Location and time of day: Establishing or altering the scene position in time and space. Blues can suggest night time while orange and red can suggest a sunrise or sunset. Gobos can also be used to project sky scenes, the moon or foliage, etc.

Projection/stage elements: Lighting may be used to project scenery or to act as scenery onstage.

Plot: A lighting event may trigger or advance the action onstage.

Composition: Lighting may be used to show only the areas of the stage which the designer wants the audience to see, and to "paint a picture”.

While Lighting Design is an art form, and thus no one way is the only way, there is a modern movement that simply states that the Lighting Design helps to create the environment in which the action take place while supporting the style of the piece. "Mood" is arguable while the environment is essential.

Then there is the four main qualities or properties of lighting namely: intensity, color, pattern and focus.

Intensity

Intensity is measured in lux, lumens and foot-candles. For any given lighting instrument or fixture, this depends upon the power of the lamp, the design of the instrument, the presence or absence of colour gels or gobos, distance from the area to be lit and the beam or field angle of the fixture and the colour and substance to be lit!

Color

Color temperature is measured in Kelvin, and gel colours are organized by several different systems maintained by the color manufacturing companies. The apparent colour of a light is determined largely by the gel colour given, but also in part by the power level the lamp is being run at and the colour of material it is to light. As the percentage of power a lamp is being run at drops, the tungsten filament in the bulb glows orange instead of more nearly white. This is known as amber drift or amber shift. Thus a 1000-watt instrument at 50% will appear far more orange than a 500-watt instrument at full.

Pattern

Pattern refers to the shape, quality and evenness of a lamp's output. The pattern of light an instrument makes is largely determined by three factors. The firstly the specifics of the lamp, reflector and lens assembly. Secondly, the specifics of how the lamp is focused affect its pattern, and lastly, a gobo or break up pattern may be applied to profiles and similar instruments. This is typically a thin sheet of metal with a shape cut into it. It is inserted into the instrument near its aperture. Gobos come in endless shapes, but often include leaves, waves, stars and similar patterns.

Focus, position, and hanging

Focus is a term usually used to describe where an instrument is pointed. The final focus should place the "hot spot" of the beam at the actor's head level when standing at the center of the instrument's assigned "focus area" on the stage. Position refers to the location of an instrument in the theater'sfly system or on permanent pipes in front-of-house locations. Hanging is the act of placing the instrument in its assigned position.

In addition to these, certain modern instruments are automated, referring to motorized movement of either the entire fixture body or the movement of a mirror placed in front of its outermost lens. These fixtures and the more traditional follow spots add Direction and Motion to the relevant characteristics of light. Automated fixtures fall into either the moving head or moving mirror category. Moving head fixtures have a much larger range of movement as well as a more natural inertial movement but are typically more expensive.

These characteristics are not always static, and it is frequently the variation in these characteristics that is used in achieving the goals of lighting.

The lighting designer

Using lighting to affect the audience's senses and evoke their emotions. The lighting designer is familiar with the various types of lighting instruments and their uses. In consultation with the director and the scenic designer, and after watching sufficient rehearsals, the LD is responsible for providing an font-size: 10.0pt; font-family: "Arial","sans-serif"; mso-fareast-font-family: "Times New Roman"; mso-ansi-language: EN-ZA; mso-fareast-language: EN-ZA; mso-bidi-language: AR-SA;">Instrument Schedule and a Light Plot. The Schedule is a list of all required materials, including color gel, gobos, color wheels, barndoors and all accessories. The light plot is typically a plan view of the theatre in which the performance will take place, with every luminaire marked. This typically includes approximate focus (the direction it should be pointing), a reference number, any accessories required, and the channel number of its connection to the dimmer system or lighting control console.

Lighting controls

Lighting control tools might best be described as anything that changes the quality of the light. Historically this has been done by the use of intensity control. Technological advancements have made intensity control relatively simple - dimmers are controlled by one or more lighting controllers. Controllers are commonly lighting consoles designed for sophisticated control over a vareable numbers of dimmers or luminaires.

The lighting controller is connected to the dimmers (or directly to automated luminaires) using a control cable (usaully DMX512), allowing the dimmers which are bulky, hot and sometimes noisy, to be positioned away from the stage and audience and allowing automated luminaires to be positioned wherever necessary.