Placing Spotlights

Editorial contributor, Paul Dybro, Ruud Lighting

Well-placed directional spotlighting (Ruud DF series) accents the water feature and provides security. The fixture is completely sealed for watertight operation. The housing is die cast aluminum and the lens tempered glass. The fixture head rotates 360????? and secures with one 1/2" locking nut. The head has a tilt range of 125????? on the adjustable fitter and locks into position with one Allen screw

When completing a customer?EUR??,,????'???s landscape lighting project, make spotlights an integral part of the overall lighting design. Spotlights can create a soothing, stimulating or dramatic effect to landscape by providing focal points and areas of interest. They can also provide safe pathway lighting and add to the feeling of security. The contrast between lighted and shadowed areas is the most important aspect of landscape lighting because it directs where and how people view landscape. Varied or asymmetrically-placed spotlights are an effective way to create that contrast.

In its Design and Installation Guide, Rudd Lighting states the paradox of landscape lighting: ?EUR??,,????'??Less is more.?EUR??,,????'?? It is the interplay of light and shadow that creates visual impact.

Drawing the lighting plan is critical. Important points to include are house outline, walks, patios, decks and pools. Spotlight placement is not an exact science. Knowing a spotlight?EUR??,,????'???s beam spread and light intensity do not provide all the information you need to place it. A lighting design created on paper or on a computer screen doesn?EUR??,,????'???t guarantee success. You should test the design. During preparation work, typically even before ordering fixtures, bring various spotlight sample fixtures to the job site at night. Place them according to the design and then move them around to change the effects the spotlights produce. Consider the landscape?EUR??,,????'???s overall appearance. Allow for additional light sources at the site, such as nearby street lamps, and then make changes. The overall effect you create may not be exactly as designed, but you should be able to create the desired lighting effects.

Also take into consideration whether a line voltage or a low-voltage system (i.e.,12-volts and transformers) is more appropriate for the project. Line voltage is commonly used in larger or more commercial applications, while 12-volt installations are more common to smaller or residential applications.

When placing spotlights, first consider the object or area the spotlight will be illuminating. Consider how the object looks from all angles. Whether you?EUR??,,????'???re spot lighting a plant, tree, sculpture, wall texture or building feature, the spotlight is there to enhance certain elements in relation to the overall landscape.

Spotlight placement is also a function of the desired effect on the lighted surface as well. The distance a light is located from an illuminated object is a critical consideration. If you want to accentuate texture, use spotlights mounted close to the surface, or mount the light further away to mute a texture.

This center-mounted fixture (Kitchler 15028) comes in three stem heights (12, 18 or 24 inches) to expand the light spreading possibilities, but how do you space them? The photometrics and suggested spacing for this particular path and spread fixture are listed on page 20.

The spotlight?EUR??,,????'???s beam pattern significantly effects the placement because the beam width can vary from very narrow to very wide. You?EUR??,,????'???ll need to experiment to determine the appropriate lamp beam pattern width to illuminate an object the way you desire. It?EUR??,,????'???s helpful to use the same lamp wattage and beam spread in an application. To vary light distribution, use accessories such as wide, soft focus, diffused or linear spread lenses to control the beam pattern and the effect it creates. Always aim lights to avoid creating glare, unless it is used to create a desired effect. Make sure that the spotlight fixture type and application follows federal, state and local codes and regulations. Use a shrouded fixture or install optional baffles or glare shields to ensure desired light beam cutoff and direct lamp visibility.

Keep the future in mind when placing spotlights. Place the fixture to ease aiming, cleaning, lamp replacement and adjustment to accommodate tree or bush growth. Also, place each spotlight to prevent damage by landscape maintenance requirements, seasonal changes or weather conditions. For example, you may need to re-aim or move a fixture during the winter to illuminate a tree trunk or branches after leaves have fallen.

In low-voltage installations, voltage drops over the distance between each fixture and the transformer. Place fixtures to minimize effects of voltage drop from the transformer. Consider using a dual-circuited transformer with three-wire cable that provides improved flexibility in load balancing.

Keeping the above considerations in mind will help you meet the needs of your customer?EUR??,,????'???s lighting project and help you earn additional business.

Photometrics for Contractors

Photometric charts are commonly used by architects and designers who need to precisely calculate light levels. This precision is important when designing municipal projects and public spaces since building codes specify minimum levels of illumination. Residential projects have no such constraints and the majority of residential designers and installers rely upon experience and onsite observation to set light levels. Still, these designers and contractors may find a municipal project at their doorsteps and may suddenly be called upon to provide precise footcandle levels.

To accomplish that, they need to use photometric charts. Photometric cone charts provide beam spread and luminous intensity at a selected distance from the lamp. Beam spread refers to the amount of surface area illuminated while luminous intensity is the level of illumination. Each type of spot lamp (a lamp with an internal reflector) has a unique cone chart with a narrow or wide cone based on the lamp design.

Fixture design also influences the cone since hoods and reflective surfaces may crop or alter the path of light from the lamp. Since photometric cone charts are not available for all fixtures, the lighting designer can use charts specific for lamp type alone with the understanding that the beam

spread may not be accurate for every fixture. In addition, reflective surfaces in the fixture and the presence of optical lenses or filters may alter the light levels.

For recommended spacing locate fixture stem height and boldface number on the chart. Read distance from fixture center above and multiply by two. Example: K-15028 on 24?EUR??,,????'?? stem (5?EUR??,,????'???x1=10?EUR??,,????'???), therefore place fixtures 10 feet apart.
table courtesy of Kichler Lighting

To most accurately determine beam spread for nonspot lamps (lamps with no internal reflectors) and fixtures with reflective surfaces, an isofootcandle chart is used that shows the lighting footprints of the fixture at varying distances. This chart is similar to a topographical map displaying concentric shapes that each represent an area of equal light level.

Photometric cone charts usually have distance and footcandles along the vertical axis and distance from center on the horizontal axis. The nonshaded area of the cone indicates the area of illumination. The designer selects a distance along the vertical axis, and notes where the edge of the cone intersects that value. From that point, the designer goes vertically down and reads the beam spread as distance from center on the horizontal axis. The footcandles are read at the same vertical level as the distance.

For example, a designer plans to install a tree light with a 35W 24????? MR-16 lamp, 28 ft. from the ground. Using the photometric chart for that lamp, the designer finds that at 28 ft., the light intensity will be 4.8 footcandles, and the beam spread will be about 7 ft. from center. However there are a few considerations, the hood on the tree light and reflections inside the hood may alter the lighting footprint. Ideally a isocandle chart for that fixture will be consulted. Also, these numbers apply to lighting a flat surface that is perpendicular to direction of the light. Since the light is angled, the footprint will be stretched depending upon that angle. (There are also charts for angles, but we won?EUR??,,????'???t go into those here!) Still, using the lamp or fixture photometric charts will give a good estimate of light levels and a good designer will combine these calculations with on-the-job experience to select the right fixtures and to meet the codes.

Note: There are software programs that allow you to create, edit, repair, report and compare luminaire photometric data, such as AGI32.com.