The primary function of lighting design, as recognized throughout the industry, is to provide visibility for the audience. Creating mood, adding to the scenery and providing effects are all secondary to the basic ability of the audience to see what is happening on the stage.
USITT lighting design standards require that a light plot--a drawing that shows the position and other information about each light used in the performance--be drafted to scale. Most common are scales where 1/2 or 1/4 inch equals 1 foot of space in the theater. The plot includes symbols that indicate the type of lighting instrument used, its location, where it is plugged in, how it is colored and whether it is controlled separately or along with other lights. Additional support paperwork expands upon this information to include spreadsheets with notes on the wattage of each lighting instrument and where it is focused. The plot must contain not only the lights, but also the architectural elements within the theater, a key to the symbols and numbers included and a title block with the designer's name, show name and date.
The widely recognized technique of McCandless lighting is recognized as a standard in the performance production industry, although it is not required. McCandless technique divides the stage into specific areas, each of which is lit with two lights that aim down at the center of the area from about 60 degrees apart. A single light aims downward toward the center of the area from the back. Each area overlaps slightly to ensure even lighting across the stage.
In addition to the front (face) light and the back light noted in the McCandless technique, other standard lighting positions include top lighting, which aims straight down onto an area from the top; high side lighting, which is hung over the stage off to the sides and angles downward across the stage; low side lighting, which is placed at stage level and shines across the stage; foot lighting, which aims upward toward the performers from the front of the stage; and practicals, which are functional elements that are visual from the stage, such as lamps and chandeliers.
USITT's publication RP-2 contains the full list of standards for each element of a light plot, including the current symbols used for each type of lighting instrument, light weight standards, and information to include. Several lighting design-specific computer drafting programs are available that can help designers uphold these standards easily and produce the support paperwork for their light plots more efficiently.