How to Focus Fixtures for an Even Wash

In Uncategorizedby tfwm

When the visual appearance of places of worship is compared, focal points and overall contrast are rarely topics of discussion. In fact, the basic visual concepts that subconsciously impact the effectiveness of any service are the same subliminal rules that guide lighting design, in television, in the movies, or on Broadway:

1. If the audience’s eyes can’t see where the sound is coming from, the audience has more difficulty hearing him/her.

2. When looking at a static (non-moving) picture, the audience’s eye is subconsciously attracted to the brightest point on a stage.

3. The audience’s eye is also attracted to the highest point of contrast on a stage; if everything is dark, the eye will subconsciously move to the single light point. If everything is light, the eye will subconsciously move to the single dark point.

So how do these concepts impact the success of your place of worship? If service leaders speak from “dark” locations, the congregation subconsciously attempts to visually find them and may not listen to what is being said. If service leaders suddenly go “dark” by moving in and out of light, the visual “flicker” is another subconscious distraction away from the service.

Though it makes perfect sense to highlight different focal points in the “performance area”, most lighting designers agree that, in this kind of presentation, the first lighting objective is to provide a consistent intensity of facial light coverage over the entire area.

Often the square footage of an altar area is large enough that it requires more than a single lighting instrument to provide an even coverage. When multiple instruments of matching color are focused so that their overlapping beams create a consistent hue and intensity over a portion or all of a performance area, those beams are referred to as a “wash” of light.

The most successful light washes are comprised of lighting instruments that are all the same type. In most cases these are fresnels, PAR Cans, or ellipsoidal reflector spotlights (aka lekos or profiles or ERS’s.). Both types of instruments can be “shaped” to prevent a portion of their light beams from illuminating unwanted visual elements in the “scene”, such as walls or pews (and congregation members) close to the altar. ERS’s use a series of internal metal pieces called shutters, while fresnels and Par’s employ external accessories called barn doors.

Understanding how to successfully design and focus a wash of lighting instruments begins by examining the components of a single beam produced by either of them. Almost every lighting instrument produces a beam (or pool, or cone) of light possessing several characteristics that are referred to when a lighting design is constructed and when an instrument is focused. Figure 1.2 shows a side view of an instrument’s beam targeted at a designer. The center of the light beam is the brightest portion of the beam, which is called the center intensity or more commonly referred to as the hot spot.

The overall size of the light beam is called the beam spread and is usually measured in degrees. The beam spread is also called the field angle, which is technically defined as the outer cone where the light diminishes to 10% of the center intensity. Approximately half of the field angle is referred to as the beam angle, which is defined as the internal cone where the light is 50% of the center intensity.

The hot spot is the portion of the light beam often targeted at the lighting designer’s head, but it can also be architectural elements. Wherever the hot spot is targeted is generally referred to as the focus point. The actual throw distance is the measured distance between the instrument and the focus point, which is used to calculate the size and intensity of light beams.

A wash is usually made up of a series of overlapping light beams. The distance between focus points is measured so that the focused beam angles are touching. Because the beam angles are the brighter portions of the light beams, the result is an even wash of light.

The first step taken to construct a lighting wash begins by determining where to place the lighting instruments. In many houses of worship this is a “given”; there is only one hanging position available to provide front light. If more than one position is available, a rule of thumb states that if all of the same kind and wattage of instruments are focused to adjacent focus points across the width of a performing area, the resulting wash will be a consistent intensity. Another rule of thumb states that the pool diameter for any light beam should be no greater than 15′-0″.

A simple drafting called a beam section is used to determine the appropriate instrument type, beam spread, and position.

Beam sections are one method used to calculate the number of instruments required for each system or wash in the light plot. In order to create the beam section, you need to have the angle information provided to you. If this information is unavailable then you can calculate it by measuring the pool of light from one fixture. The optical design of most instruments is such that the area of the beam angle is typically at least 50% of the overall field angle. Therefore by measuring the pool from one fixture you simply divide by two to calculate the beam angle.

Once you have the beam angle/pool size information, you can calculate the quantity of fixtures for a wash. In the next illustration the field angle is in gray and the beam angle pool is in white. Note how the beam angle pools are just overlapping, this will provide for an even wash. Calculate the number of fixtures based on the area being lit divided by the size of the beam angle pool.

After the lighting wash has been successfully focused, these final words:

A wash of light can’t be taken for granted, before each service check that all of the instruments are functioning.

The instruments’ reflectors and lenses should be cleaned as part of a regularly scheduled maintenance. Each ERS’s beam should be individually checked and aligned when needed to assure that its “hot spot” remains in the center of the beam.

If there are any colored gelatins used in your lighting design they should be checked more often. If you find you are replacing them often, consider purchasing glass filters instead.