Event Lighting Design: Part One

Lighting can be thought of as one of many raw materials the event producer has at his or her disposal. It is the job of the Lighting Designer or LD (usually from a subcontracted lighting supplier), to manipulate the light beams emanating from fixtures or luminaires to achieve the look desired by the event producer or manager. The LD has five qualities of light that can be varied and massaged to do this. These qualities are intensity, distribution, color, direction, and movement. Over the course of the next two or three blog posts, I will cover the basics of these qualities.


Intensity 

In simplest terms, this refers to the strength of a light source. However, there are some other relative measurements that are also associated with a light source and what happens when the light is projected over a distance and strikes an object.


Intensity is the strength of a light source (e.g. the actual lamp inside the light fixture), or the light output. It is measured in lumens or candles. Illuminance is the light level actually falling on the surface of an object being lit. It is measured in lux (metric) or foot-candles (imperial). 1 foot-candle = 10.76 lux. Brightness is the effect of light leaving the surface of an object being illuminated. It is what the human eye actually sees. It is affected by the intensity of the light source, the distance from the source to the object, and the properties of the object (e.g. color and texture). It is measured in foot-lamberts. The figure below illustrates the differences amongst these three terms.

        Light Strength 

Actually, this relationship can be calculated mathematically using what is known as the inverse-square law, E = I/ D², where E is the illuminance in foot-candles, I is the luminous intensity in lumens, and D is the distance in feet between the source and the point of calculation on the surface. For example, using a light source that produces 6000 lumens, the light density on a surface 10ft. away would be 60 foot-candles = 6000/(10)(10), and 20ft. away would be 15 foot-candles = 6000/(20)(20).

Generally speaking, objects that appear bright draw more attention to themselves. Because of this, it is the job of the LD to ensure that those objects needing attention, whether they be performers or decorative, are appropriately bright. 

Distribution 

Distribution refers to the manner in which light strikes a surface and reveals an object.

It can be applied to how objects appear, in that they might be softly lit as part of a larger scene with light that has no sharp edges. On the other hand, they may be individually lit with a small, sharply defined, single light beam.

On another level, distribution can be applied to the appearance of light that uses an image projector of some sort, such as a gobo in front of an ellipsoidal fixture or an actual projector. These in turn produce certain desired images on a surface such as a wall or scrim. 

On a third level, distribution can be applied to the shape of a light beam itself when viewed through smoke or haze effects. 

I will cover color in the next post.