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Specification-Grade LED Lighting Terminology: The Terms that Matter

Specification-Grade LED Lighting Terminology: The Terms that Matter

Every industry has its own special terminology. In the fast evolving lighting industry, the technical jargon can sometimes be confusing even to industry insiders.

In a never ending battle to promote the advantages and technical superiority of their new LED products, some manufacturers turn their efforts to pouring on the technical jargon in their product specification sheets. The idea is to impress specifiers with advanced technology. Some of this jargon is valid and impressive, and some are just over-hyped synonyms for existing technology.  There are also time-honored catch phrases that exist in every lighting catalog but are rarely understood.


Photometric Optimization – When fixture manufacturers engineer lamp positions, reflectors and/or louver profiles ensure that the maximum amount of light leaving the lamp(s) will end up in the task area, as opposed to being trapped inside the fixture or bouncing uselessly around the room.

LPW – refers to the Lumen Per Watt ratio. Just as an automobile’s fuel efficiency is measured in miles per gallon, light bulb efficiency is measured in terms of lumens per watt—the amount of light produced for each watt of electricity consumed. More lumens per watt means more light for less electricity.

Troffer – As the name implies, troffers are trough-shaped recessed ceiling fixtures (the term is derived from the terms “trough” and “coffer.” LED Troffers are fast replacing troffers with fluorescent lamps. A parabolic troffer refers to a recessed fixture that has a louver with a parabolic cross section. The parabolic shape redirects light rays from the light source into parallel rays that shine in a controlled fashion into the room.

VCP – Visual Comfort Probability. This is a obsolete fixture rating system that determines how many people would, when viewing this fixture, find it to have low glare and be comfortable to work near. The higher the number or percentage, the better.

See Also

Semi-Specular – This refers to the image one would see in a reflective surface. A true specular reflector would act similar to a mirror where one could clearly see the reflective image. A semi-specular image would produce a more diffuse, less clear and a less glaring image, which is a desirable type of reflector used in a lighting fixture.

Luminaire – A complete lighting fixture.


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