Primary use of outdoor lighting is during night time to illuminate outdoor areas for improved visibility, security, and aesthetics. However, it is important to understand how much of exterior illumination is sufficient enough and how to balance the need for light while minimizing light pollution and increasing energy efficiency. Illumination levels lower or higher than the optimum level reduce visibility and are unable to serve the purpose.
Inappropriate design, use of inefficient lamps and poor operation of outdoor lighting not only results in wastage of light and poor illumination quality, but also contributes to high electricity consumption. This in turn contributes to increased operating cost and high levels of greenhouse gas emissions. Outdoor lighting covers a wide range of applications, including building façade illumination, landscape lighting(parks/ sculptures), underwater lighting, floodlight/sports lighting, Street and Roadway lighting, Parking Lot and Garage illumination and Signage lighting. Commonly used outdoor lighting sources are Fluorescent lamps, compact fluorescent lamps, High Pressure Sodium Vapour Lamps, High Pressure Mercury Vapour Lamps, Metal Halides and Light Emitting Diodes. A few lighting techniques used to achieve these applications are as below,
Up Lighting: Up Lighting is achieved by mounting the fixture on the ground and aiming the light upwards on an object creating a dramatic effect. This form of lighting gives an unusual effect which is never seen in nature and is usually reserved for highlighting focal points. This technique’s flair for drama augments large shadows that could be considered design elements in the scene themselves. Wall washing and grazing, large specimen tree lighting and ornamental shrub illumination are all achieved through Up Lighting techniques.
Back Lighting: In addition to down lighting, the other major technique that comes from nature is Backlighting. Silhouetting of plant material or art objects against softly washed walls is a common scene in a professional outdoor lighting.
Downlighting / Security Lighting: Downlighting is the technique of lighting objects and areas from above. Interior lighting involves light fixtures mounted in ceilings for task lighting, artwork lighting and general highlights within a space. Facade lighting involves under canopy lights, wall washers to architectural elements or wall mounted downlights to vertical elements of a building. In exterior landscape areas downlighting imitates nature and creates the most natural effects. Light fixtures mounted within trees can simulate moonlighting as the light filters through leaves and branch structure and cast graceful shadows and outlines on the ground. This technique is very desirable for safety and security lighting.