Theatrical Lighting: Center Line Section (Sections)
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Center Line Section (“Sections”)

Center Line Section (“Sections”)

The color key helps you figure out the angle of the light you want in plan view; but not the distance or height of the light. To determine which pipe to hang the light on; the lighting designer must do a “section”. Occasionally a copy of the “center line section” (often just referred to as a section) will be supplied with the theatre base plans – and very rarely by the set designer.

Again: Request a copy of the plans for the theatre you’re going to be working in, and a list of available equipment.
You can also ask if there's a Repertory Lightplot available - many theatres have one which is flexible in its design. Don't just copy it; but you can use it as a guide to see what light sources (inventory) have traditionally been used from what position.

Since spaces (and inventories) vary greatly; it can be helpful to visit / explore the space if possible. I recommend standing in your planned acting areas and physically pointing to the various hanging positions; paying particular attention to the angle of your fully extended arm which will serve as a good rough estimate for how resulting shadows will fall on the performers.

Salsibury Theatre Base Groundplan
Salsibury Theatre Base Section

Salsibury Theatre Lighting Inventory
Salsibury Theatre Repertory Lightplot

Some venues will also have their space available as a CAD (Computer Aided Drawing) file format (.dwg file) which you may be able to use or import into your own software to use as a base for your Lightplot. Be sure to ask!
Here is another local venue's information packet for comparison… some spaces I’ve worked in don’t have a scale drawing at all (so I had to create my own!)
Hering Auditorium Theatre Base Groundplan
Hering Auditorium Base Section

Creating a quick section:
A) Lay vellum over the plan
A) Lay vellum over the plan
View larger Typically since no one else will see this drafting; the lighting designer often makes a very quick and rough (messy) section just for their purposes.
The easiest way to create a section is to lay a sheet of vellum over the plan…
B) Draw a line for the floor
B) Draw a line for the floor
View larger Draw a line for the floor (you don’t have to make cross-hatching; this graphic was made for clarity).
C) You can see where the pipes are located from the groundplan you’ve prepared; and the trim height of the pipes should be part of the theatre specs.
Section Pipe animation
View larger If the theatre has a fly system or the electrics are on winches, you must determine the height of the pipes yourself. Fly (or counterweight) systems are usually in proscenium theatres, in which case, setting the trim height at 2’ below the proscenium opening is typically a good place to start.

D) Sketch in your actors (average height: 6’-0”) near where they will be standing.
E) Then draw a line to represent the angle of throw desired.
Draw desired angles
View larger
Typically 45° is considered optimal; though a range of between 30°- 60° is standard.
Lights are often focused on performer’s chests so that their face is in the beam angle (brightest part of the light) but their feet are still lit too!
F) This shows us our target positions, and we can determine approximately how far our lights will be from the performers.
Figuring out the distance from the actors.
View larger
Often, some or all of our optimum targets don’t line up perfectly in which case the designer must decide which compromise to accept.