Consider the effect of a light starting as a vertical downlight on an actor then moving in a frontal plane until its beam becomes horizontal and then carries on to light from below. How visible will be the actor's face, particularly eyes and teeth? To what extent will face and body be modelled or flattened? What area of stage will be selected and what will be the size and direction of shadows cast on floor and scenery?
A vertical beam is the most selective light possible. The lit area of stage, and the shadow cast upon it, need be no wider than the widest part of the actor. However, the actor's eyes will be black pools and a highlighted nose will shade the mouth.
If the light comes from a little forward of the actor, it will start to reach the eyes and mouth (provided that she keeps her chin up and is not defeated by a hat brim!). However, the lit area, and shadow cast, starts to extend upstage from the actor - i.e. the light is slightly less selective
As the lighting comes increasingly from the front, the actor's eyes and teeth receive more light. But the area lit extends further and further upstage, reducing the selectivity and increasing the likelihood of the actor's shadow hitting the scenery
As the light becomes more and more frontal, the actor's features become flattened (and so also does three dimensional scenery). The lit area and the actor's shadows increase until, when the light is horizontal, there is a lit corridor for the entire depth of the stage, and the actor shadows become actor length.
Light from below projects an actor shadow that looms above the actor rising and falling as she moves towards and away from the light source. When this is the only lighting angle, the effect on the face is not at all natural. But a little from below, usually just reflected light can help to soften the harshness of light from above.
Now consider a light from behind. Then a light or lights from a series of side angles (i.e. lights at right angles to those considered above). Once again the criteria is visibility, modelling, selectivity and shadows.
A light source behind the actor does not illuminate the face, but it helps to give depth to the stage by separating the action from the scenery through creating a haze and highlighting head and shoulders. The shadow of the actor is cast forward, helping the selection of areas. Since the light does not fall on the face, strong colours can be used.
If the light comes from a little to one side of the actor it will start to reach the eyes and mouth on that side. The area lit, and the shadows cast, will extend along the stage floor on the other side.
Add a second light source from the other side, and both sides of the face will receive light. However, there is now a second shadow and the selected area of stage floor extends to both sides of the actor.
As the side lighting comes from an increasingly lower angle, the shadows will lengthen to both sides of the actor and a larger corridor will be selected across the stage. As the light hits the face from a lower angle, it will light more into the eyes and teeth, although there will still be a tendency towards a central dark line where the beams meet down the centre of the face.
As the angle lowers, sidelight has an increasingly modelling effect on the actor's face and body. This is particularly important in dance. When the light becomes horizontal there will be a lighting corridor across the whole stage. By focusing just clear of the floor, it is possible to lose shadows into the wings, and the light will only be apparent when an actor stands in it.
We normally seek to light an actor for maximum visibility and maximum modelling, with minimum shadow. Additionally in many productions, we need to select as tight an area as possible. Which combination of angles offers the optimum compromise?
The basic compromise that has long been the standard approach is a pair of beams crossing on to the actor (one for each side of the face) from positions that are both forward and to the side of the actor. The suggested angle is often around 45 degrees in both directions - i.e. midway between vertical and horizontal and midway between front and side. However to restrict the shadows cast and to give a better 'join', the lights are often positioned closer to the vertical and to the centre.
A backlight added to the basic crossed pair brings depth to the scene and generally enhances the 'look' of the actor. The backlight can be used for strong atmospheric colour if required, while the crossed pair maintain a more natural tint on the actor's skin tones. Note: The actor is now It by three beams with a 120 degrees separation between them.
The problem with 'crossed pair' lighting (with or without a backlight) is the extent of the spread of light on floor and scenery beyond the area where the actor's head is lit (remember that head is usually about five feet above the floor). Although a single beam can be flat it can also be quite tight.
Adding a backlight can enhance this flatness quite considerably - and the selectivity is still a tightly controlled upstage/downstage corridor without side spillage.
For modelling, sidelights can be added and, although they will spread the lit area, they can be at quite steep angles since they do not need to make a major contribution to visibility. Note: Four beams now light the actor with a 90 degrees separation between them
The major proportion of a stage lighting rig is focused to form a palette of areas and colours whose various combinations will provide the desired fluidity of selectivity and atmosphere. However there are certain lights whose function is so 'special' that they cannot make a significant contribution when mixing the basic palette.
Specials usually consist of spotlights set so tightly that the spaces they light cannot be considered as areas. They are often for moments when an actor has to be picked' out (perhaps only head and shoulders) on an otherwise blacked-out stage. They need to be listed in a priority order for close scrutiny and reduction to essentials.
There may be a request for equipment to produce clouds, flames, water, lightning, etc. When listing it is always prudent to remember that such effects can draw attention away from the actor rather than positively support a performance. And if the effect is essential, then the effect of light reflected from fire or water is often more telling than a pictorial representation of the actual fire or water.
The proportion of the rig focused on the scenery will be very small. With the exception of skies and back or front cloths, scenery normally gets sufficient general wash from the reflected light bouncing off the stage floor from the lights that have been set for the actors. Indeed, as discussed in the following pages, many of the basic problems of lighting design arise from difficulties in stopping actor light hitting directly on the scenery Successful lighting of scenery depends on augmenting the diffuse reflected general light by selective highlighting of chosen scenic elements, or parts of these elements. This can vary from bold gashes to soft emphasis. Again, to be listed and reduced to essentials after a debate based on priorities and available resources..