Outdoor Lighting Glossary
Come across a lighting word you aren't sure of? Completely new to the world of lighting? We feel your pain! Here you will find a collection of terms and concepts that should help to make your life easier.
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Select the first letter of the word from the list above to jump to appropriate section of the glossary.
Dark Adaptation - The process by which the retina becomes adapted to a luminance of less than 0.01 footlamberts.
Diffuser - A translucent piece of glass or plastic sheet that shields the light source in a fixture. The light transmitted throughout the diffuser will be redirected and scattered.
Diffusion - The scattering, spreading or redirection of light in an even manner, by a lens, to achieve some intended effect such as reduced glare.
Dimming Ballast - Special fluorescent lamp ballast, which when used with a dimmer control, permits varying light output.
Direct Current (DC) - Flow of electricity continuously in one direction from positive to negative.
Direct Glare - Glare resulting from high brightness or insufficiently shielded light sources in the field of view. It usually is associated with bright areas, such as luminaires, ceilings and windows which are outside the visual task or region being viewed.
Disability Glare - Glare resulting in reduced visual performance and visibility . Often accompanied by discomfort glare.
Discharge Lamp - A lamp in which light (or radiant energy near the visible spectrum) is produced by the passage of an electric current through a vapor or a gas.
Discomfort Glare - Glare producing discomfort. It does not necessarily interfere with visual performance or visibility.
Distribution Panel - Box containing circuit breakers or fuses where power is distributed to branch circuits.
Downlight - A type of ceiling luminaires usually fully recessed, where most of the light is directed downward. May feature an open reflector and/or shielding device, can be recessed, surface mounted, or suspended.
