A sightline is a straight line from an eye to a point on the stage, and it is either interrupted or it is not. Everything else in this article follows from that, including several problems that are usually attributed to bad luck in seating.
The worst seats define the acting area
Lines drawn from the two extreme seats of the widest row cross somewhere upstage. Inside that crossing, everything is visible to everybody. Outside it, part of the audience sees an actor and part sees masking.
This means the usable stage is defined by the ends of the house rather than by the centre. A designer working from the production desk, which is invariably in the middle, is working from the one position that never reveals the problem. Drawing the lines on the plan early costs an hour; discovering during previews that a third of the house cannot see the bed costs a restaging.
Vertical is a separate calculation
The horizontal case gets the attention and the vertical case produces the complaints. Two mechanisms operate.
Rows have to rise enough that each person sees over the head in front of them, and auditorium design guidance treats that rise as a specific quantity rather than an impression. On a flat floor with temporary seating there is no rise at all, and beyond the third row nothing below chest height exists.
A balcony overhang cuts the picture from above for everyone beneath it. Flown scenery, a projection surface high on the back wall and anything happening on a raised level are simply absent from those seats, and the audience underneath frequently does not know what they missed.
What the overhang does to the sound as well
Seats under a deep balcony receive less of the room's reverberant energy, because the overhang shields them from the volume above, and the high frequency content that arrives directly is not supplemented. The result is a drier, duller sound than the same production delivers to the stalls, which is a sound problem originating in an architectural decision, and it is the reason those seats often need their own loudspeakers.
Sightlines are not static
They change when the person in front leans forward, when a latecomer is seated, and when the house stands. The last one matters disproportionately.
Wheelchair positions are frequently placed at the back of a level or at the end of a row, which are locations chosen for access rather than for view, and at the moment an audience rises to applaud, every one of those patrons loses the stage entirely. It is a known problem with a known answer, which is positions with a raised floor or a clear line over standing heads, and it is a design decision rather than an operational one.
Masking is the other half of the drawing
Sightlines determine not only what the audience can see of the stage but what they can see past it. The same lines that cut off the upstage corners from the side seats also reveal the wings, the crew standing by, the back of a flat and the glow of a monitor, to exactly those seats and no others.
Masking is therefore drawn from the same lines and in the same pass. A production that plots its acting area from the extremes and then hangs borders and legs by eye has done half the work, and the half it skipped is the one visible from the cheapest seats. Checking from those seats, with the working lights off and the crew in their running positions, is the only test that finds it.
Everything else in the house has sightlines too
A surtitle panel, a caption display, an assistive listening receiver that has to be seen to be used, a describer's booth window: each has its own visibility from each seat, and each is usually positioned after the seating plan is fixed.
The article on surtitles deals with the attention cost of a panel that can be seen. A panel that cannot be seen from some seats is a service those patrons do not have, whatever the equipment list says.
Selling a restricted view honestly
Some seats in old buildings cannot be fixed, and selling them is better than not selling them. What matters is that the description is specific enough to be useful: which part of the stage is lost, whether a pillar is involved, whether the loss affects the whole performance or one scene.
A generic warning attached to a whole block, and a price reduction, tell a patron nothing about whether they will be able to follow the show.
What we cannot verify
Auditorium design guidance differs between countries and between professional bodies, and the quantities involved are set out in those documents rather than here; we reproduce no figure. Whether a specific seat is usable is a question about that building, answered by sitting in it during a technical rehearsal, which is a check very few productions schedule and most would benefit from.
The short version
- The extreme seats, not the centre, define what part of the stage is usable.
- The production desk is in the one position that never shows the problem.
- Row rise is a specific quantity; a flat floor has none of it.
- A balcony overhang removes flown elements and dulls the sound underneath.
- When the house stands, badly placed wheelchair positions lose the stage entirely.
- A restricted view is sellable; a vague warning about one is not useful.