# TB0015
I.
Introduction
II.
Why are aiming angles important
III.
Why is photometry of the fixture important
IV.
Summary of Light-Structure Green
™
features that control spill light and glare
I. Introduction
Purpose: Spill light and glare are a nuisance for nearby neighbors and the community. This
bulletin discusses ways to limit spill light and glare.
Scope: The scope of this bulletin is limited to lighting design. There are other things a property owner can do to limit spill and glare. For example: build fences or plant bushes or trees.
Spill light illuminates areas off the field of play, which can be a nuisance for nearby neighbors.
Glare is the discomfort experienced when looking directly at a light source. The design elements that affect offsite spill light and glare are basically the same, so this discussion is relevant for both. The two primary design elements that control spill light and glare are the fixture aiming angle and fixture photometry. Both elements need to be coordinated within the design to properly control offsite spill light and glare.
In addition to preventing light trespass on neighboring properties, another benefit of controlling spill light is that fewer fixtures and less electrical power may be required to light a field, since less light is wasted.
See Technical Bulletin # TB0005 for a more detailed explanation of spill light and glare.
II. Why are aiming angles important
The vertical aiming angle is a key element in controlling the amount of light that is directed onto the field, with steeper aiming angles generally directing more light onto the field resulting in less spill and glare off-site. The two factors that determine the vertical aiming angle are fixture mounting height and pole setback, assuming a fixed aiming point. Below are examples showing how mounting height and setback affect aiming angles.
A. Fixture Mounting Height
Mounting height is typically the factor that is most easily adjusted in a lighting design, since pole locations are frequently subject to various constraints. The higher the mounting height, the steeper the vertical aiming angle. The steeper the aiming angle, the less spill light and
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glare that result. The effect of mounting height on spill and glare can be seen in the example below.
Example #1: A single NEMA 4M 1500W Light-Structure Green fixture is aimed to the center of a soccer field. The only difference in this example is the mounting height; all other parameters (aiming point, pole setback, fixture type, field size, etc.) remain the same. In the illustration, the edges of the light beam represent the rays at which the beam’s intensity is
10% of the maximum candlepower.
As shown in example #1, the taller mounting height produces a steeper aiming angle which distributes more light from the fixture onto the field, thereby decreasing the spill light and glare for the nearby house.
B. Pole Setback
The closer the setback, or closer the pole is to the edge of the field, the steeper the vertical aiming angle. The steeper the aiming angle, the less spill light and glare that result. The effect of different setbacks can be seen in the example below.
Example #2: A single NEMA 4M 1500W LSG fixture aimed to the center of a soccer field.
The only difference in the example is the setback of the poles; all other parameters (aiming point, mounting height, fixture type, field size, etc.) remain the same.
As seen above in example #2, the pole with the closer setback produces a steeper aiming angle which directs more light from the fixture onto the field, thereby decreasing the spill light and glare for the nearby house.
# TB0015
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Decreasing the setback can create shadows on the field of play and when too close can cause a hazard for players. When considering decreasing pole setback, the lighting designer will evaluate on-field lighting and safety along with off-site spill and glare concerns.
III. Why is photometry of the fixture important
Fixture photometry defines the light distribution characteristics of a fixture, essentially describing the shape and intensity of the beam. Since photometric characteristics differ between fixtures, selecting a fixture with appropriate beam control is very important.
IV. Summary of Light-Structure Green features that control spill light and glare
•
Reflector System – Hundreds of photometric patterns in their proper application provide minimal spill light for each project
•
Visor System – Multiple visor choices provide efficient light on the field and minimal spill light
•
Side Shift Beam Control – Beams can be adjusted within the luminaire horizontally and vertically, enabling the lighting designer to custom fit light to the field.
•
Die-Cast Housing – Protects the optics of the system from damage ensuring photometric performance throughout the life of the system.
•
Factory Aiming of the fixture to the tenth of a degree ensuring light is placed where it is intended.
The purpose of this document is to provide an educational reference for specific technical issues that affect the quality and performance of a sports lighting system.
Prepared by:
Draft date:
Chad McSpadden
July 31, 2001
Released:
Revised:
May 23, 2002
N. Tippett, 10/25/07, S. Vander Wiel 01/20/11
# TB0015
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