The A… of A Vocabulary List

Last fall I took, and passed, the Lighting Certification exam offered by the NCQLP ( I even got a handsome little lapel pin!

Preparing for the exam involved a good deal of memorizing, as it is rather broad in scope and replete in detailed questions. So while studying I created a vocabulary list, which grew to 76 pages of words related to the physics of light and various techniques for describing light, measuring light, and determining how much of what kind of light to use where and when.

The list included a lot of words with descriptions that ranged from well-worded and informative to seemingly nonsensical phrases, which actually did made sense to me. So I decided that being as how I is a a certified technical writer, having all the learnings needed and what not, I would go back and edit the vocabulary list and make it available to anyone who happened upon my internet presence. This proved to be more time-consuming than I imagined, although I have made it through to D after a few days work spread out over a month.

Yesterday I sat down to convert the Word document into a .pdf, but wouldn’t you know Windows 10 and Adobe have to work out some relationship issues. So rather than a nice .pdf of letters A through D, I am posting letter A, right here in this post.

Oh, BTW, for any technical writers who might glance at this, I have not yet decided the format I am using for citations.



Above finished Floor (AFF)

Is the area of a room that is above the finished floor. It is a concept used in determining the room cavity ratio for lumen method calculations.

Absorptance (A or α)

Is the effectiveness of a material at absorbing light, or the extent to which a material does not reflect or transmit light. The formula for absorptance is the amount of absorbed light divided by the amount of incident light:


Describes a substance that responds to light of short wavelengths, usually in the UV category causing a photochemical reaction. The retina, rods, and cones of the eye are actinic and can be damaged from prolonged exposure to UV wavelengths.

Action Spectra

Is the rate of a physiological activity plotted against wavelength of light. It shows which wavelength of light is most effectively used in a specific chemical reaction. (Wikipedia 2-18-2016) Action Spectra is a term used when discussing the effects of various electromagnetic wavelengths on the circadian rhythms in humans, that is blue light versus amber light.

Adaptation Luminance

Is the range of luminance of and background objects in the field of view. The adaptation luminance affects the threshold at which changes in brightness are perceived by the human eye. High adaptation luminance is when the range of luminance in the field of view is small, so very slight changes in light level are registered. Low adaptation luminance is when the range of luminance in the field of view is large, so only more extreme change sin light level are registered.

Adaptation luminance is measured and considered in lighting for tasks areas, roadways and other places where performance of vision based tasks is important.
(IES Handbook Ver. 10)

Aging Vision

When the eyes age the following things happens:

  • The cornea yellows, so that at about 50 years old there is a 40% reduction in transmission.
  • The pupil gets smaller, letting in less light.
  • The lens loses resiliency and cannot be focused as easily.

Ambient Light Layer

Is the light layer that provides illumination for walking around a space and recognizing people and things. The ambient light layer is often a combination of direct luminance and reflectance.

American National Standards Institute (ANSI)

Is a standards organization.

As the voice of the U.S. standards and conformity assessment system, the American National Standards Institute (ANSI) empowers its members and constituents to strengthen the U.S. marketplace position in the global economy while helping to assure the safety and health of consumers and the protection of the environment.

The Institute oversees the creation, promulgation and use of thousands of norms and guidelines that directly impact businesses in nearly every sector: from acoustical devices to construction equipment, from dairy and livestock production to energy distribution, and many more. ANSI is also actively engaged in accreditation – assessing the competence of organizations determining conformance to standards. (, 2-18-2016)

Americans with Disabilities Act (ADA)

Is a federal statute that ensures provision of certain accommodations for disabled person, such as that light switches and sconces at certain levels.

Ampere (Amp)

Is the unit of the flow rate of electrical charges in terms of the number of charged particles passing a point, or the amount of charge of each particle. If the number of charged particles, or the amount of charge in the particles, passing the point increases there are more amperes and therefore higher amperage.


Is a process that uses a combination of chemical baths and electrolytic processes to develop an oxide layer on the surface of a metal, thus increasing the metal’s durability and resistance to corrosion.


Is the standard energy code for all buildings except low-rise residential buildings. It is a set of standards agreed upon by the three ANSI, ASHRAE and IESNA.

Arc Tube

An arc tube is the inner bulb in gas discharge lamp. It houses the two cathodes which, when connected by voltage, create a light source.

Architectural Lighting

Is lighting that is part of the construction of the building itself and is incorporated into the other building systems, as opposed to portable lighting installed by occupants.

Architectural Lighting Design

Is a field within architecture, interior design, and electrical engineering that is concerned with the design of lighting systems, including natural light, electric light, or both, to serve human needs. (Wikipedia 8-16-15.)

America Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)

ASHRAE, founded in 1894, is a global society advancing human well-being through sustainable technology for the built environment. The Society and its members focus on building systems, energy efficiency, indoor air quality, refrigeration and sustainability within the industry. Through research, standards writing, publishing and continuing education, ASHRAE shapes tomorrow’s built environment today. ASHRAE was formed as the American Society of Heating, Refrigerating and Air-Conditioning Engineers by the merger in 1959 of American Society of Heating and Air-Conditioning Engineers (ASHAE) founded in 1894 and The American Society of Refrigerating Engineers (ASRE) founded in 1904. (ASHRAE website 2-18-2016)


Is a general term that describes reduction in the strength of a signal, whether digital or analog. Attenuation is also referred to as signal loss and extinction. It is a natural consequence of signal transmission over long distances. Attenuation is considered when planning power and control cable distances for luminaires.

Authority Having Jurisdiction (AHJ)

Is the agency or person with the authority to approve electrical installations and construction. The AHJ could be the fire marshal, the electrical inspector, the building inspector, or a party designated by the building team. The AHJ inspection is part of commissioning.

Average Exitance

Is the mean surface density of emitted luminous flux (light) passing through, or reflected off, a material or surface. Exitance is measured in lm/ ft2 or lm/m2. NOTE: There are also Radiant Exitance, Spectral Exitance.

Average Illuminance

Is the mean surface density of incident flux (light) onto a surface. Illuminance is measured in footcandles (lm/ ft2) or lux (lm/ m2).

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