A lighting plot is a scale drawing of the lighting rig, laid over the theatre's groundplan, with one symbol for each fixture. It shows where every lantern is hung, what type it is, and the information a crew needs to rig, cable, patch and focus the rig: its position, its control channel, its color, and often what it is there to do. Read alongside the rest of the lighting paperwork, it is the drawing that turns a design into something a team can actually hang.
What the plot shows
Because it sits on the groundplan, the plot is drawn to the same scale as the other set drawings, commonly 1:25 or 1:50 in the UK, so the lighting positions line up with the scenery beneath them. That alignment is the point: a designer can see whether an overhead bar will reach the acting area, or whether a boom in the wings will be masked by a flat, before anyone climbs a ladder to find out. The plot shows the hanging positions as well as the fixtures on them: the overhead electrics, or LX bars, often numbered from downstage as LX1, LX2 and so on; front-of-house positions out over the audience; vertical booms and ladders at the sides; and any units rigged on the set or standing on the floor.
What each symbol tells you
Each fixture is drawn as a symbol whose shape indicates the type of unit. A profile spot, a Fresnel, a PAR and a moving light each have a different outline, so the character of a rig, hard-edged or soft, fixed or moving, can be read from the drawing alone. Around each symbol sits a small cluster of numbers and marks. Not every plot carries all of them, and their placement varies, but the common ones are worth knowing:
| Notation near the symbol | What it usually tells you |
|---|---|
| Control channel | The number the operator brings up to make that light do something |
| Color | The filter, given as a number (Lee and Rosco are the usual ranges) rather than a color name |
| Unit number | Which fixture it is on that particular bar or position |
| Dimmer or DMX address | Where the unit is powered from, or its address on the control network |
| Beam angle or wattage | How wide or how strong the unit is |
| Accessories | A gobo, an iris, barndoors or similar, where fitted |
Exactly what appears, and where it sits in relation to the symbol, varies from designer to designer.
Why every plot carries a key
This is why a plot is drawn with a key. There is no single symbol set used everywhere: conventions differ between countries, drawing offices and the software a plot is drawn in, and a designer may work to a house style or a particular symbol library. Published standards exist, such as the USITT graphic standard in the United States, but they are not followed universally. The key, sometimes called the legend, sets out which symbol means which type of fixture and how to read the notation around it, so that anyone can interpret the drawing without guessing. A plot without a key is only fully legible to the person who drew it.
How to read a plot
Reading a plot is a matter of working from the general to the particular. Begin with orientation: like the groundplan beneath it, the plot is usually drawn as seen from above with the audience at the bottom of the page, which means stage right falls on your left as you look at it. Find the centre line and the plaster line, then locate the hanging positions. Take one position at a time, and for each fixture read its type from the symbol and its channel and color from the numbers around it.
It helps to remember that the plot answers only some of the questions, and is meant to be read next to the other paperwork. The channel hookup lists every channel in order with the fixtures on it, which is how an operator or programmer works. The magic sheet lays the rig out by what each light is for, by area or system rather than by where it physically hangs, which is closer to how a designer thinks during a plotting session. The plot tells you where; the hookup and the magic sheet tell you what and why. Reading a rig usually means moving between them.
Drawing and reading a plot digitally
Lighting plots were once drawn by hand on a board, and many designers still rough out positions on paper early on. Most finished plots are now drawn in CAD or dedicated lighting software, which keeps the symbols consistent, builds the key as you work, and takes the pain out of the constant small revisions a rig goes through.
In Setplot the plot is drawn on the same metric groundplan as the set, so the two stay in register. You add the hanging positions (bars, booms, ladders and the rest), hang and focus fixtures on them, and give each one its channel, color, beam angle and trim height. Because the fixtures are part of the design rather than marks on a separate drawing, the paperwork follows from it: the scaled plot, the channel hookup and the patch are derived from the same information, so a change made once appears everywhere. The plan can also be viewed as a white-card 3D model, which lets you check whether a beam lands where it should and whether a boom clears the scenery, and a production can hold a different lighting state for each set in the show. The core tools are free, including before you make an account, which makes it a workable place to learn how a plot fits together.
However it is produced, a plot does one job: it holds the whole rig in a single drawing, so that anyone who can read the symbols and the key can tell, before anything is rigged, what light the stage will get and where it will come from.