A term used for the luminous intensity of a light source.The intensity in anyone direction from the standard candle is called one candela (formerly one candlepower; cpl).

Color Rendering Index (CRI)

A measurement of the color shift an object undergoes when illuminated by the light source, as compared to a reference source at the same color temperature. Color rendering is measured on an index from 0-100, with natural daylight and incandescent lighting both equal to 100. Objects and people viewed under lamps with a high color rendering index (CRI) appear more true to life.

Color Temperature

The chromaticity of an ideal "black body" when it is heated to a specific temperature in Kelvin (K). It is the measure of the color of light, not actual temperature.


A unit used in measuring direct illumination. It is defined as the illumination produced from a source of one candela at a point on a surface of one foot away and perpendicular to the source of light. One lumen per square foot.


The result of the use of light, illuminance, the density ofluminous flux on a surface, is usually measured in footcandles.

Inches to Metric Conversion

To calculate the metric equivalent of inches in millimeters (mm) use the following formula: inches x 25.4001 = millimeters.

Instant Start

A circuit used to start specially-designed fluorescent lamps without the aid of a starter. The circuit utilizes higher open circuit voltage than is required for the same length preheat lamps, to strike the arc instantly. This circuit is used today in slimline and cold cathode lamps. Instant start 40-watt bipin lamps are made with a short circuiting device built into the base.

Kilowatt (KW)

A larger unit of power, a thousand watts (watts x 1000 kilowatts).

Kilowatt Hour (KWH)

The measure of electrical usage from which electricity billing is determined. For example, a 100-watt bulb operated for 1000 hours would consume 100 kilowatt hours, (100 watt x 1000 hours = 100 KWH).At a billing rate of $0.10/KWH, this bulb would cost $10.00 (100 KWH x $0.10/KWH) to operate.

Lamp Dimensions

Bulb designations consist of a letter or letters to indicate the approximate diameter in eights of an inch.

Lamp Listing Sequence

Lamps are listed in wattage sequence within their groups.