Landscape lighting is one of the most artistic lighting design disciplines. Its primary purpose is ambience—to make nighttime spaces aesthetic and inviting. On a more practical level, it can extend the usable hours of a site, facilitate wayfinding, improve safety and provide a sense of security.
Despite using many of the same techniques, landscape lighting is very different than interior lighting, though it has much in common with theatrical lighting. Interior lighting often requires soft and uniform general lighting, with higher brightness contrast used to establish focal points. With landscape lighting, the idea is to light only what needs to be lit, treating what isn’t illuminated—what’s kept in the dark within the lighted field and outside it—as a design element of equally important consideration.
Shadows can conceal while adding texture and drama to what is seen with light. Additionally, they can create safety and security hazards by concealing, for example, stairs, changes in elevation and criminals. Part of achieving the right contrast is to avoid high levels of brightness unless required. In landscape lighting, we typically deal with very low light levels compared to a building interior. We also often favor point sources, which produce stronger shadows.
The Illuminating Engineering Society (IES-RP-39) defines three major landscape lighting applications: traverse lighting (for walking); converse lighting (for walking and talking, requiring light that enables people to see each other’s facial expressions); and task lighting (for doing things like grilling on a barbecue). Each application has its own needs in terms of light level and optimal light distribution. For all, the designer must make avoiding glare a top priority, and, again, light should only be placed where it is needed, avoiding stray and spill light emitted into the sky or onto neighboring property.
Serving these applications is a toolbox of techniques.
Decorative lighting provides ambient or task lighting. It is commonly used for pathways. The luminaire itself is a decorative element in the field of view.
Accent lighting is a powerful directional lighting technique that highlights architecture and landscape features we want people to see, such as sculptures and trees, creating focal points in the field of view. Typical luminaires include in-ground uplights and above-ground bullet luminaires.
Backlighting is an interesting technique that lights an object from behind and often from above. It can silhouette an object or be used with frontal lighting to model the object and make it visually pop against its background. Typical luminaires include uplights and downlights, such as floodlights and bullet luminaires.
Frontal lighting is a general technique involving lighting an object’s front side from one or more angles. One type of frontal lighting is grazing. A luminaire is placed close to an object or surface and lights it from the top or bottom, creating rich shadows in textured material such as rock and brick. The closer the luminaire is placed to the material, the stronger the shadows, providing artistic choices. Wall washing using diffuse sources (like fluorescent), and placed to produce uniform illumination, can be used to highlight the object or surface while concealing texture. To avoid scallops (patches of dark between the luminaire light patterns), place the luminaires closer together.
Downlighting, also called moonlighting, involves mounting luminaires in a tree and aiming them at the ground. The result is a soft pattern of light and shadow on the ground that produces a pleasing moonlight effect. Higher mounting heights will enrich the effect and reduce light levels on the ground. One method is to place a single luminaire at the top and center of the tree and aim it straight down. For larger trees, additional luminaires may be mounted closer to the outside of the tree. Another method is to mount multiple luminaires at varying heights close to the center of the tree and aim them down and out at various angles. The angled light may be aimed at nearby smaller trees, shrubs and foliage. Another method is to aim a single luminaire out from the rear of the tree, but be sure not to place luminaires too close together. While luminaires can be aimed during the day, adjustment and tuning should occur at night. When mounting in trees, account for tree growth, and use the right equipment.
The result of these techniques is a series of potentially dramatic effects. Modeling involves striking an object from the front with a key light and then adding dimension by striking it with fill light from at least two directions. Silhouetting involves backlighting to render the object as a dark outline against a luminous background. Shadowing involves striking objects such as plants with light, projecting shadows onto a wall, while uplighting can be used for dramatic accent lighting, including backlighting.
Landscape lighting design is an art and science that can enrich the nighttime environment. To learn more, consult RP-39, published by the Illuminating Engineering Society.