One really wants to have a few things. Enough time to do a proper design, hang the show, and rehearse the technical elements before you have to go in front of an audience. Enough lights and dimmers and consumables to accomplish something useful and pretty. A script is nice, too.
And then there's shows where you are already working three jobs, the script is still being written, and the rented hall is between management teams: coming off a long string of other productions, and everything is mis-labeled if not broken outright. The design I just completed was one of those.
Lighting for the stage has two tasks, two tasks which somewhat blend into each other. The first is functional; to put light on actor's faces. Live theater is all about being in the same room with a live human being who needs to express themselves through voice and features, and you need to see those features. (Or, in the case of dance, see their body, as that is the expressive organ there.)
This sounds simpler than it is. Unlike a portrait photography studio, a stage is large. You have to put those lumens across the width and into the depth of it, and evenly; so an actor in the back left is equally as visible as one in the front center. The angle needs to be low and straight enough so shadows are not cast across the face. The colors need to be neutral enough so they look reasonably human and in the appropriate health (yellow and green, as well as some of the lavender range, will make people look jaundiced, as well as bring out any blotchiness in their complexion).
And yet, there needs to be enough angle and color and complexity to reveal the planes of the face. A simple flat front in white light is like a bad flash photograph; all you get is a white oval, with no definition. No character.
Thus the complex variety of schemes -- and the large number of discrete lighting instruments with all the associated wiring, dimmer requirements, ladder access and time spent, documentation, and so forth to accomplish just this basic task. As a generic rule, unless you have huge surpluses available the majority of your lighting assets are going to go towards simply "putting light on faces." Even when you have the options for multiple systems, a majority of the lights will still have that as one of their tasks -- if not their primary task.
The second task is artistic. And that is to make use of the light as one of the tools to enhance mood, to indicate location and season and time of day, to underline enhance or provide certain specific items or events called for in the story, and more than anything else, to make distinctions. To make clear when a play is going on and when it has yet to start. To make clear when the action has moved from one location to another, or into a different emotional space, or gone through some other important change (such as an inner monologue or an audience aside). That is, light is also used to focus the audience's attention and make distinctions spatially and temporally.
This idea of differentiation is why one of the two major approaches I apply is to find these divisions, these changes, these axes of something that changes. They may be simple poles, or they may be a continuum; in the latter, think of Under Milkwood in which the period of the play covers a single day, with the changing of the hours, the sunset and moon and dawn, being of equal importance to the physical location within the town.
In, say, "Two Gents" (that is, Two Gentlemen of Verona) the major axis is town versus woods, as the action flips back and forth scene to scene from one to the other. Which leads us naturally to "Midsummer," in which the woods is a magical place and quite distinct from the town, but the thrust of the play is absolutely dependent on the difference between the woods during the day and the woods at night.
And you can often achieve these axes within your area plan; that is, within the same lights that give you that necessary and functional light-on-faces. A typical scheme is to cover the areas with three lights each. Say, one warm and one cool, matched against a neutral. By changing the relative levels or omitting one of the three, you change the look.
And if this is super-imposed on an area plot -- that is, on those banks of lights necessary to cover the width and depth of the stage -- you also have given yourself the ability to focus in on one specific part of the stage. That is, it allows you to isolate and separate to make it clear that the action stage left is taking place in a different country or time than the action simultaneously occupying stage right, or so it is clear the monolog's the thing, and the people moving around upstage are merely shifting scenery and should be ignored. And, of course, to focus the audience's attention more sharply on that corner of the stage where the most important action is taking place.
This degree of control pretty much happens whether you need it or not. And that is because it is extremely rare to be able to plug everything in to the same place. Theater instruments are power hogs; the standards are 750 and 1000 watts, plus the increasing number of energy-saving 575W lamps. The math rapidly becomes instinctive; two of the big ones, or four of the small ones, to any particular circuit. Anything more means wires on fire, breakers popping, expensive repairs to dimmer packs.
And why is this? Scale, again. Think of it this way; if you have a two-bedroom apartment, you could probably get away with plugging every wall lamp, chandelier, desk light and so forth into a single wall outlet. But these lights rarely top 250 watts; the faces they are trying to light are not much more than five feet away, and the total space is lucky to be twenty feet on a side.
Even a black box theater space is twice that dimension, meaning four times the area, meaning at a first approximation it would take four wall outlets to power those lights (regardless of what the lights actually were). Of course, theatrical lights are directional, not omnidirectional like most household lighting -- but theatrical lights also (for various reasons) need to push more lumens than the lights in your living room.
(As another comparison, insolation at the Equator is about a thousand watts per square meter. Out here in northern latitudes and with cloudy days the average is less, but basically think of a 500 watt light bulb pointing at every single square meter of ground when you are outside during the day. Theatrical lighting -- even movie lighting -- is a good magnitude less than that. And that's why theater lighting designers hate matinees.)
And, yes, you can light a scene with a single candle. I've done it. But it took half an hour of progressively dimmer cues to dark-adapt the audience to that moment. But back to circuiting. At the theater I just opened a show at, the built-in wiring over the stage -- and the rack-mount dimmers, dating from the 70's -- could handle up to four instruments on a channel.
Out in the house, all I had available were "Elation" portable dimmer packs. Very useful for small and traveling shows, these are four 5A dimmers in a little box that can be hung on a lighting batten or tucked behind scenery. And at 20A total, they can be (and often are) plugged into a standard wall outlet. At 5A a channel, though, that's one instrument. Period. And even if you could power more, the wiring is extension cords and cube taps, none of which are rated for more than 15-20 amps. And, yes, there's a very narrow window by which the Fire Department allows theaters to pull crap like this.
The point being, that I have individual control of each and every light just as a side effect of having to get power to them. So you leverage this by carefully planning the focus points in what most of us call an Area Plot. That is, you plan so when you turn off three and leave two up, those two define a part of the stage that, at some point in the action, you will find it useful to define.
When you have the inventory you cover the stage multiple times; each cover is with different angles, in different colors, and otherwise in different qualities of light. This allows you to make those changes that make it clear to the audience the story-telling point, "Here we are in the Forest of Arden" as well as the emotional point, "It's spooky here in the woods."
Covering from a multiplicity also brings the light around the face and body to clear up obscuring shadows, and provides a controlled contrast to reveal contours. This is why one of the most common area light schemes remains to this day the one developed by Stanley McCandless in 1932; two lights separated by a 45 degree angle, one of them gel'd "cool" and the other "warm," so that they mix together to white light. Many variations are possible.
And this brings me at last to my most recent design. A tale within a framing story within a prologue. The prologue is modern-day and was written to be performed in one, that is, in front of the main rag, that is, with the curtain closed. We couldn't get the curtain to work so this removed one of the options that would have otherwise made that distinction clear.
The other distinctions I wanted to make clear were the difference between framing story scenes -- taking place amongst the travelers on pilgrimage to Canterbury, aka the Canterbury Tales -- and within the tale being told; that of Arthurian legend. And within that legend, I wanted to be able to delineate between interior (Camelot) and exterior (the generic woods where knights-errant find adventure). And lastly, I wanted to be able to find a moonlight look both in support of specific dialog and also as an emotional underscore to Sir Gawain's journey (and, says the playwright, as a foreshadowing of the fall of Camelot -- which does not take place within this particular story).
And I didn't have the assets. An additional wrinkle (no pun intended) is that the minimal set design included a cyclorama. That is, a large seamless cloth that covers the entire back of the stage. The typical way to light a cyc is with specialized fixtures called variously strips, striplights, and cyc strips. These achieve the usually-desired even coverage of this flat plane by using a large number of individual lamps arranged in a line. Usually (but not always) grouped electrically by threes or fours, allowing you to put different colors in each set and thus produce various blended colors on the surface.
I had some old ones but the wiring was shot and would need to be re-done. Rental, upon investigation, was beyond our finances. That left an old trick; re-purpose a bunch of par cans. The original par light was basically an automobile headlight in a tin can. Newer ones are built around purpose-designed lamps, and the most recent designs omit the integrated lamp-reflector-diffusor assembly (aka a headlight) for standard theatrical lamps and interchangeable front lenses.
The very latest wrinkle is LEDs. The great attraction of these is real-time color changes within a single fixture, as they are built with red-blue-green, or that plus amber, or even plus amber and white. A second and not small advantage is they don't take up a dimmer, and also don't require much power; a whole bank of seven of these things could easily and safely be powered from a single extension cord. And since they take DMX-512 control, a single daisy-chained data cable is enough to control them all.
This left me with only fresnel lens fixtures in sufficient number to light the acting areas. That is; these are theatrical lights with a hemispherical reflector and a fresnel lens on the front, giving a soft-edged light that can only be gently shaped by means of barn doors; metal flaps that are attached to the front. I lit my areas flat and with a high angle, and gel'd them in x09; that is, I colored them by placing pieces of transparent polyester manufactured with carefully controlled tinting by high-temperature dyes. The Roscolux series number 9 is a warm, pleasing amber reminiscent of candle-light.
My intent was that this read as candles for the framing story, and as warm and somewhat old-fashioned (like the famous sepia tints of the Kansas segments of The Wizard of Oz) for the tale-within-the-tale. This was combined with a daylight blue -- x65 -- from the top back, standing in for the blue-ish light of a clear sky, and I had just enough instruments left to double this system with an additional set of back lights in x79; a deep green-blue for a moonlight effect.
I had a very small number of ellipsoidals. Also referred to by lighting people as ERS for Ellipsoidal Reflector Spotlights, these are in fact instruments with a stack of plano-convex lenses much like a camera or telescope, with the light focused into a theoretical point by an ellipsoidal reflector placed behind the lamp. This quality of being brought into a tiny focal point means you can produce a hard edge, shaping it with shutters that slide into this small gap. In addition, a piece of metal punched out with patterns can be slipped into this spot, and that pattern will be reproduced faithfully at the point where the beam is in focus.
One of these instruments I hung almost directly overhead to isolate (and, emotionally, to "crush down") Gawain at a particularly bad moment for him. And, more importantly, to allow the rest of the stage to go dark enough to permit a "dead" body to be dragged off without the audience seeing.
Another I gave a stock foliage pattern and threw that over the stage in an attempt to make the outdoors scenes seem more outdoors. This only partially worked; you need a lot more light, a lot more instruments to carry that trick off properly. It did however provide a nice bit of magic for one scene where I was able to reduce the rest of the front lights and let the foliage show up properly.
The last two provided a method to keep the framing story -- and the oft-present narrators from that story -- in the light without putting them in the world of Camelot. Gel'd in a distinctly different amber, they were additionally framed in gothic window shapes. Which were not available when I stopped by the lighting supply story, so I purchased a roll of blackwrap -- the manufacturer calls it Cinefoil -- and cut out the shapes I needed with an Xacto knife.
All in all, there is a lot less flexibility in the plot than I would like. I didn't have the sheer power to allow me to change intensities or bump at the end of songs. I didn't have the color choices to make different looks through the longer musical numbers (about all I could do was dial up different colors on the cyc). But I did manage to achieve good coverage and modeling that felt "right" for the environments I was describing, that gave some sense of evolving and changing through the changes of the story, and that provided some contrasts. And there was just enough left for a few "special" moments here and there.