Modern stage lighting is a flexible tool in the production of theatre, dance, opera and other performance arts. Several different types of stage lighting instruments are used in the pursuit of the various principles or goals of lighting.
Functions of lighting
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:
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.
Revelation of form: Altering the perception of shapes onstage, particularly three-dimensional stage elements.
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 lavender light.
Location and time of day: Establishing or altering position in time and space. Blues can suggest night time while orange and red can suggest a sunrise or sunset. Use of gobos to project sky scene, moon 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.
Qualities of lighting
The four main qualities or properties of lighting are intensity, color, pattern and focus.
Measured in lux, lumens and foot-candles. For any given luminaire (lighting instrument or fixture), this depends upon the power of the lamp, the design of the instrument (and its corresponding efficiency), 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, the colour and substance to be lit, and the neuro-optics of the total scene (that is, the relative contrasts to other regions of illumination).
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 it, 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 full 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.
LED fixtures create colour through additive colour mixing with red, green, and blue LEDs at different intensities. This type of colour mixing is also used frequently with borderlights and cyclorama lights to create different colours on stage and on the cyclorama. Another form of colour mixing is CMY, or subtractive colour mixing. Cyan, magenta and yellow dichroic filters are used in different percentages to create different colours. Because it is often difficult to create true reds and greens, a green dichroic filter is often added to fixtures using this method of colour mixing.
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 first are the specifics of the lamp, reflector and lens assembly. Different mounting positions for the lamp (axial, base up, base down), different sizes and shapes of reflector and the nature of the lens (or lenses) being used can all affect the pattern of light. Secondly, the specifics of how the lamp is focused affect its pattern. In ellipsoidal reflector spotlights (ERS) or profile spotlights, there are two beams of light emitted from the lamp. When the cones of both intersect at the throw distance (the distance to the stage), the lamp has a sharply defined 'hard' edge. When the two cones do not intersect at that distance, the edge is fuzzy and 'soft'. Depending on which beam (direct or reflected) is outside the other, the pattern may be 'thin and soft' or 'fat and soft.' Lastly, a gobo or break up pattern may be applied to ERSs 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 many 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's fly 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 / scanner category. Scanners have a body which contains the lamp, PCBs, transformer, and effects (color, gobo, iris etc.) devices. A mirror is panned and tilted in the desired position by pan and tilt motors, thereby causing the light beam to move. Moving head fixtures have the effects and lamp assembly inside the head with transformers and other electronics in the base or external ballast. There are advantages and disadvantages to both. Scanners are typically faster and less costly than moving head units but have a narrower range of movement. Moving head fixtures have a much larger range of movement as well as a more natural inertial movement but are typically more expensive.
The above characteristics are not always static, and it is frequently the variation in these characteristics that is used in achieving the goals of lighting.
Stanley McCandless was perhaps the first to define controllable qualities of light used in theater. In A Method for Lighting the Stage, McCandless discusses color, distribution, intensity and movement as the qualities that can be manipulated by a lighting designer to achieve the desired visual, emotional and thematic look on stage. The McCandless Method, outlined in that book, is widely embraced today. The method involves lighting an object on the stage from three angles- 2 lights at 45 degrees to the left and right, and one at 90 degrees (perpendicular to the front of the object).
In the context of lighting design, a lighting instrument (also called a luminaire) is a device that produces controlled lighting as part of the effects a lighting designer brings to a show. The term lighting instrument is preferred to light to avoid confusion between light and light sources.
There are a variety of instruments frequently used in the theater. Although they vary in many ways they all have the following four basic components in one form or other:
Box/Housing - a metal or plastic container to house the whole instrument and prevent light from spilling in unwanted directions.
Light Source (lamp).
Lens or opening - the gap in the housing where the light is intended to come out.
Reflector - behind or around the light source in such a way as to direct more light towards the lens or opening.
Additional features will vary depend on the exact type of fixture.
Most theatrical light bulbs (or lamps, the term usually preferred) are Tungsten-Halogen (or Quartz-Halogen), an improvement on the original incandescent design that uses a halogen gas instead of an inert gas to increase lamp life and output. Fluorescent lights are rarely used other than as worklights because, although they are far more efficient, they cannot be dimmed (run at less than full power) without using specialised dimmer ballasts and they will not dim to very low levels. They also do not produce light from a single point or easily concentrated area, and have a warm-up period, during which they emit no light or do so intermittently. High-intensity discharge lamps (or HID lamps), however, are now common where a very bright light output is required, - for example in large follow spots, HMI (Hydrargyrum medium-arc iodide) floods, and modern automated fixtures. When dimming is required, it is done by mechanical dousers or shutters, as these types of lamps also cannot be electrically dimmed.
Most instruments are suspended or supported by a "U" shaped yoke, or 'trunion arm' fixed to the sides of the instrument, normally near its center of gravity. On the end of such, a clamp (known as a hook-clamp, C-clamp, or pipe clamp - pipe referring to battens) is normally fixed, made in a "C" configuration with a screw to lock the instrument onto the pipe or batten from which it is typically hung. Once secured, the fixture can be panned and tilted using tension adjustment knobs on the yoke and clamp. An adjustable c-wrench (US) or spanner (UK) is often used to assist the technician in adjusting the fixture.
All lights are loosely classified as either floodlights (wash lights) or spotlights. The distinction has to do with the degree to which one is able to control the shape and quality of the light produced by the instrument, with spotlights being controllable, sometimes to an extremely precise degree, and floodlights being completely uncontrollable. Instruments that fall somewhere in the middle of the spectrum can be classified as either a spot or a flood, depending on the type of instrument and how it is used. In general, spotlights have lenses while floodlights are lensless, although this is not always the case.
Traditionally theatre and stage lighting has been of the "generic" type. These are lights which are focussed, geled, and then simply dimmed to give the effect the designer wants. In recent years the emergence of moving lights (or automated lights) has had a substantial impact of theatre and stage lighting.
A typical moving light allows the designer to control the position, colour, shape, and strobing of the light beam created. This can be used for exciting effects for the entertainment or dancefloor use. Moving lights are also often used instead of having a large number of "generic" lights. This is because one moving light can do the work of several generics.
Please note: In the UK the nomenclature is slightly different from North America. This article primarily uses the North American terminology. Although there is some adoption of the former naming conventions it has been normal to categorise lanterns by their lens type, so that what in the US is known as a spotlight is known as a Profile or a Fresnel/PC (Pebble/Plano/Prism Convex) in the UK. A Spotlight in the UK often refers to a Followspot. The following definitions are from a North American point of view, and would be confusing when used, without further clarification, in the UK. UK naming conventions are considered to be correct in most of the world, in fact most North American theatres will also use the UK terms except when talking in a more general sense (ie get a spotlight to focus on that set piece, or 'flood this area')
Also note: In Australia and many other places, the lamps inside a theatrical fixture are referred to as bubbles. In North American English, a bubble refers to the protrusion that occurs when one's body (or other oily substance) contacts the lamp. Oil will cause the portion of the lamp which has oil on it to expand when it is on (lamps generate a lot of heat), creating the bubble, and causing the lamp to explode. That is why one should never directly touch the glass portion of a lamp. Cleaning with rubbing alcohol will remove the oil.
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 - solid state dimmers are controlled by one or more lighting controllers. Controllers are commonly lighting consoles designed for sophisticated control over very large numbers of dimmers or luminaires, but may be simpler devices which play back stored sequences of lighting states with minimal user interfaces. Consoles are also referred to as lighting desks or light-boards.
For larger shows or installations, multiple consoles are often used together and in some cases lighting controllers are combined or coordinated with controllers for sound, automated scenery, pyrotechnics and other effects to provide total automation of the entire show. See show control.
The lighting controller is connected to the dimmers (or directly to automated luminaires) using a control cable (e.g. DMX512) or network, 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. In addition to DMX512, newer control connections include RDM (Remote Device Management) which adds management and status feedback capabilities to devices which use it while maintaining compatibility with DMX512; and ACN (Architecture for Control Networks) which is a fully featured multiple controller networking protocol. These allow the possibility of feedback of position, state or fault conditions from units, whilst allowing much more detailed control of them.
A dimmer is a device used to vary the electrical power delivered to the instrumentís lamp. As power to the lamp decreases, the light fades or dims. It is important to note that some color change also occurs as a lamp is dimmed, allowing for a limited amount of color control through the dimmer. Fades can be either UP or DOWN, that is increasing or decreasing the intensity. Today, most dimmers are solid state, although many mechanical dimmers still exist.
Dimmers are often found in large racks that draw large amounts of three-phase electrical power. The dimmers themselves are often removable modules that range from a 20-amp, 2.4 Kilowatt unit to a 50-amp or even a 100-amp unit. They can often be replaced by a Constant Power Module which is basically a 20- or 50-amp breaker in a dimming module casing. Constant Power Modules are used to supply non-dimming current to other electrical devices (like smoke machines, chain winches, or scenic motors). When a Constant Power Module is installed, the corresponding circuit is energized as long as the dimming pack is on, independent of the lighting console.
Increasingly, with the growth of digital technology, modern lighting instruments are available which allow remote control, not just of intensity, but of direction, color, beam shape, projected image, beam angle and a wealth of other effects. The ability to move an instrument ever more quickly and quietly has become the industry goal. Such automated lights frequently have built-in dimming and so are connected directly to the control cable or network and are independent of external dimmers.