1st Generation T8s (also called 700 series or basic grade)

Full wattage T8 lamps with CRI in the 70s and not the best lumens. F32T8s have about 2800catalog or photopic lumens.

2nd Generation T8s

Mid-grade 800 series T8 lamps. Typically these F32T8s have 2950 – 3000 catalog or photopic lumens.

3rd Generation T8s (also called high performance or super)

Also called high performance, super and high lumen 800 series T8 lamps. F32T8s that typically have 3100 catalog or photopic lumens.

735, 841, 850, etc.

Nomenclature for many fluorescent lamps. First digit stands for CRI. 7 means CRI in the 70s. 8 means CRI in the 80s. Last two digits stand for Kelvin. 35 means 3500K. 41 means 4100K. 50 means 5000K.

800 Series

Fluorescent lamps with CRI in the 80s.


Typical household incandescent light bulb. A stands for arbitrary. 19/8” (2 3/8”) is diameter.

Ambient Lighting

General lighting typically from ceiling mounted lighting fixtures.


Material used in some fluorescent lamps to improve light output in cold and hot temperatures.


Required to operate fluorescent and HID lamps. There are both magnetic and electronic ballasts.

Beam Spread (beam angle)

Angle of reflector lamps listed in degrees or terms, like spot and flood.

BEF (Ballast Efficacy Factor)

Way to compare how efficient ballasts are driving the same number of same type of lamps. BEF = BF x 100 / system wattage.

BF (Ballast Factor)

How hard a ballast drives a lamp. Higher BF means more light and more wattage. Lower BF means less light and less wattage. Lamp lumen and wattage ratings in lamp catalogs based on 1.0 reference ballast.


Typically 2’ long narrow U-bend fluorescent lamp


Light intensity in a direction. Mainly for reflector lamps.

CBCP (Center Beam Candlepower)

Only for reflector lamps. Intensity (candela) at center of beam.

CCT (Correlated Color Temperature)

Blackbody temperature in Kelvin degrees that looks like light source. (For example as a piece of iron is heated it turns red, then yellow, white and then bluish white.) Look at Kelvin.

CEM (Certified Energy Manager)

AEE’s certification for qualified energy managers.

CLEP (Certified Lighting Efficiency Professional)

AEE’s certification for qualified lighting professionals.

CMH (Ceramic Metal Halide)

MH with very high CRI. Also called ceramic pulse start metal halide.

Cold Cathode CFL

Type of CFL that has about double lamp life compared to typical CFLs.

Color Quality Scale

This may replace CRI, because it better with LEDs.


One of the three photoreceptors in the human eye. Responsible for color discrimination. Photopic function.

CEE (Consortium of Energy Efficiency)

Lists high performance T8 lamps and ballasts, which many rebate programs use. www.cee1.org

CRI (Color Rendition Index)

How natural do colors look. Daylight and incandescents are considered to have a perfect 100.

CW (Cool White)

Most common CRI and Kelvin type for T12 lamps. 60 CRI & 4100K.


With regard to rated lamp life. Typically 3 hours on, 20 minutes off, 3 hours on, etc. for fluorescents. Typically 10 hours on, 20 minutes off, 3 hours on, etc. for HID

Design Lumens (or mean lumens)

Lumens at 40% of lamp life.


Equivalent of a ballast for LEDs.


This is fancy term for efficiency. Lumens per watt. (like miles per gallon)

Energy Saving F32T8s (or reduced wattage T8s)

These include 25, 28 and 30 watt lamps. There are several limitations with these lamps.

EOL (End Of Life)

This can be used for EOL lumens.


Fluorescent 17 watt Tubular 8/8” (1”) diameter lamp (2’ long).


Fluorescent 32 watt Tubular 8/8” (1”) diameter lamp (4’ long).


Fluorescent 34 watt Tubular 12/8” (1.5”) diameter lamp (4’ long) (used to be called energy saving F40T12 lamps).


Fluorescent 54 watt Tubular 5/8” diameter High Output lamp (almost 4’ long).


Fluorescent 96” long Tubular 12/8” (1.5”) diameter lamp (For some lamps, especially ones longer than 4’, the number after F stand for length instead of wattage).

FC (Foot Candles)

The amount of light that hits a target. What light meters measure. Horizontal fc are usually measured 30” above floor, which would be like putting light meter on a desk. Vertical fc are measured vertically like on a wall.


Also known as lighting fixture or luminaire.

Fixture Efficiency

Percentage of light that gets out of the fixture compared to light emitted by lamp(s).


Lamp family that the interior phosphor coating transforms UV energy into visible light.

Full Spectrum Lighting

Often a marketing hype term to sell lamps and bulbs at outrageous prices.

GEB (General Electronic Ballast)

Not extra efficient ballast.


Incandescent lamp type with higher efficacy than common incandescents.

Halogen Infrared

Higher efficacy than standard halogen.

Hibay (High Bay)

Interior lighting fixtures often considered at least 25’ high. Typical kind of lighting fixture in gyms and warehouses. Very similar to lowbay.

High Performance

This typically relates to Consortium of Energy Efficiency’s approved T8 lamps and ballasts.

HID (High Intensity Discharge)

This lamp category includes MH (metal halide), HPS (high pressure sodium) and mercury vapor. Lamp catalogs often also include LPS (low pressure sodium).

HPS (High Pressure Sodium)

This high intensity discharge lamp type provides a yellow color that has about a 22 CRI.

Human Centric Lighting

Lighting which can improve circadian rhythms, alertness, sleep, mood, visual acuity, performance, etc. http://humancentriclighting.com/


This is density of light on a surface. It is measured in footcandles.


Fluorescent lamp type without cathodes, so really nothing to wear out. Typically 100,000 hour rated lamp life. Some lamp manufacturers include in HID section.


Lamp type that the heated filament glows. Typical residential lamp type.

Initial Lumens

For lamps the amount of lumens after 100 hours of operations

IS ballast (Instart Start)

Mainly for T8s. Ballast does not preheat lamp cathodes before starting lamp(s). Parallel wired so if one lamp burns out, remaining lamp(s) function normally. Most popular type of ballast for T8 lamps, because of lower cost, higher efficiency and fewer wires. But can shorten lamp life.


Temperature used to indicate correlated color temperature of a light source. Kelvin uses the same degree size as Centigrade, zero for Kelvin is –273 degrees C.

KW (kilowatt)

1000 watts.

KWH (kilowatt hour)

This is what the majority of utility electric bills are based on. Examples of 1 KWH are running a 1000W light bulb for 1 hour and running a 10W light bulb for 100 hours.



Rated life of LED products, when have 70% of initial lumens.

Lamp life (rated life)

Rated lamp life is middle of a bell shape curve when half of the lamps have burned out and half are still working under laboratory conditions. Look at cycles for more info.

LC (lighting certified) Certification by the NCQLP is the closest thing that the lighting industry

has to PE (professional engineer) certification in the engineering realm. www.ncqlp.org

LED (light emitting diode)

One type of solid state lighting.


Interior lighting fixtures similar to hibay, but often considered less than 25’ high. Typical kind of lighting fixture in gyms and warehouses.

Low voltage

Typically 12V.


LM-79 establishes testing methodology to create a level field for product evaluation. It looks at 25C ambient, power supply, stabilization, orientation, electrical instruments, and testing equipment. LM-79 defines what information is required; total light output, voltage, current, power, calculates efficacy, lumen distribution, CCT, CRI, spectral distribution, testing lab, and equipment used. LM-79 requires that solid state lighting products be tested to “Absolute Photometry.” Conventional HID/Fluorescent uses “Relative Photometry.” Absolute Photometry is lumen output of LED based luminaires and is dependent on the chip, thermal management, drive current, and optical system. LED based luminaires and lamps must be tested as a complete unit or system. Only DOE recognized CALiPER testing laboratories results should be utilized.


Measuring lumen depreciation of LED light sources, arrays and modules. It does not include complete products. It does not define or provide complete product life.

LPS (low pressure sodium)

Ugly yellow light. Zero CRI. Common for exterior pole lighting in cities like San Jose and San Diego that have nearby observatories. Sometimes considered an HID.


Amount of light that a light source generates in all directions. This is listed in lamp catalogs.

Lumen Depreciation

Decrease in lumen output as lamp ages.


Can be considered as brightness of an object or surface.


Fancy name for lighting fixture. Complete lighting unit consisting of housing, lamp sockets, lamp(s), ballast(s), and applicable reflector(s), louver(s) and lens(es).


About 10 lux equals 1 footcandle.

MBCP (maximum beam candlepower)

Same as CBCP.

Mean lumens (also design lumens)

Lumens at 40% of lamp life.

Mercury Vapor

An HID lamp. Half as efficient as HPS and MH. Half as efficient Only good application is lighting pine trees.

MH (metal halide)

Good white light lamp in HID group. Includes standard/probe start, quartz PS start & ceramic PS (CMH).


Multi Reflector 16/8” (2”) diameter. 12V, which is low voltage.

NCQLP (National Council on Qualifications for the Lighting Professions)


Occupancy Sensor

Control that automatically turns lights off based on no occupancy. Can also be set to automatically turn lights on.

PAR (Parabolic Aluminized Reflector)

Typical for PAR38 and PAR30 halogen spots through floods.

Parabolic or Parabolic Louver

Often 4” x 4” openings that bare lamp can be seen through. Most common fixture type is 2’ x 4’ 18 parabolic cell troffer.

PCBs (polychlorinated biphenyls)

Very toxic substance in ballasts manufactured before 1980.


Cone response in human eye.


Common term for 5, 7, 9 or 13W two-pin one-loop CFLs. PL is originally a Philips term. GE calls them BX. Sylvania calls them CF. Generic term is CFT(wattage)W/GX23/8XX.

Probe Start MH

Same as standard MH.

PS Ballast (program start or programmed start)

Also called programmed rapid start. Improved version of rapid start. Preheats lamp cathodes, before starting lamp(s). Usually series wired, so if one lamp burns out, other lamps also dim or turn off. More expensive and less efficient than IS ballasts.

Photometry (photometrics)

Measuring visible light or computer generated fc layouts.

PS MH (pulse start MH)

MH with starter in the lamp. Includes both quartz PS MH and ceramic PS MH (CMH).

Pupil Lumens

Lumens based on scotopically or spectrally enhanced lighting.

Color Quality Scale

May replace CRI, because includes bright or saturated colors.


Most common type of this incandescent lamp is 300W double ended, which is shaped like a pencil.

Quartz PS MH (quartz pulse start metal halide)

One of the two types of pulse start metal halide.

R (reflector)

The R is code for reflector lamps.


Amount of red in LEDs

Restrike Time

This is the time that a hot lamp requires to turn back on after it has been turned off. This can be 15 minutes for many MH lamps. Fluorescents have no restrike times.


This is one of the three photoreceptors in the human eye. Scotopic function.

RS ballast (rapid start)

Ballast that preheats lamp cathodes before starting lamp(s). Usually series wired, so if one lamp burns out, other lamps also dim or turn off. Being phased out and replaced with program start ballasts.


Rod response in human eye. Peak response in blue portion of the visible spectrum.

S/P (scotopic/photopic)

This ratio is available from lamp manufacturers. GE lists them in their paper and web catalogs.

SPD (spectral power distribution)

Graph of the radiant power emitted by a light source as a function of wavelength. SPDs provide a ‘finger print’ of the color characteristics throughout the visible part of the spectrum.

Spectrally Enhanced Lighting

Older name was scotopically enhanced lighting. Lighting with more blue content, which increases perceived brightness and acuity.

Standard MH (or probe start)

This older type of MH is also called probe start metal halide, which has the starter in the lamp.

Super T8s

Same as high performance, high lumen and 3rd generation T8s.

Suspended Indirect Fixture

Suspended or pendant fixture that provides significant to all uplight. This is very popular in new and remodeled office buildings

T5, T5HO, T8, T12, etc.

For these linear fluorescent lamps, T stands for tubular and the number stands for how many eights of an inch in diameter. HO stands for high output.

Task Ambient Lighting

Combination of task lighting and ambient lighting. With the task lighting, the ambient lighting amount is reduced.

Task Lighting

Lighting directed at desk or other specific surface or area to illuminate certain tasks like reading. Most common task light application is under cabinet in module office cubicles.

Task Modified Lumens

Lumens based on scotopically or spectrally enhanced lighting. Three classifications are brightness, paper tasks and computer tasks.


IES’ Technical Memorandum-24-13, which is about the benefits of high Kelvin lighting.

Triple Looper CFL

4 pin compact fluorescent lamp with three loops. Most common are 18, 26, 32 and 42W.


Long recessed lighting fixture that bottom is usually flush with ceiling. Most common type is 2’ wide by 4’ long that are very typical in offices.


Dimming and warm to cool white color or complete color changing. Also called dimming and Kelvin changing or shifting.

W (watt)

Unit of electrical power. Lamps and ballasts are rated in watts to show the rate they consume energy.

Warm Up Time

The time it takes for a cold lamp to reach at least 90% of maximum light output. This can be quite long for some HID lamps.

This glossary was written and is provided by:

Stan Walerczyk, HCLP, CLEP, LC

Principal of Lighting Wizards

Chair of Human Centric Lighting Committee

Various white papers and other documents are also available on those websites.

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