Glossary
| Beam Angle | The beam angle is the degree of width that light emanates from a light source. The angle between those points on opposite sides of the beam axis where the intensity drops to 50% of maximum |
| Candela | A very small square of semic conduction material. Also known as a “die”, it is the “active” light-emitting component of an LED. |
| Color Rendering Index | The color rendering index (CRI), sometimes called color rendition index, is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in color-critical applications such as photography and cinematography |
| Colour Temperature | The color temperature of a light source is the temperature of an ideal black-body radiator that radiates light of comparable hue to that of the light source. Color temperature is only meaningful for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e. those on a line from reddish/orange via yellow and more or less white to bluish white; it does not make sense to speak of the color temperature of e.g. a green or a purple light. Color temperature is conventionally stated in the unit of absolute temperature, the kelvin, having the unit symbol K. |
| Cool white | Cool white light, 4100K – 4200K |
| Daylight | Daylight, cold white light, 5000K – 6500K |
| LED | A light-emitting diode (LED) is a two-lead semiconductor light source. It resembles a basic pn-junction diode, which emits light when activated. |
| LED driver | It is a self-contained power supply that has outputs matched to the electrical characteristics of LEDs. |
| Lightbulb socket (cap, base) | Lamps are usually inserted in lampholder sockets which provide electrical connections to the lamp and support it in the lighting fixture. There are many different standards for these lampholders, created by de facto and by various standards bodies. A general coding system is a letter or abbreviation followed by a number. |
| Lumen | The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. |
| Luminous efficacy | Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total power (electric power, chemical energy, or others) consumed by the source. |
| Warm white | Warm white light, 2700K |
| Watt | The watt (symbol W) is a derived unit of power in the International System of Units (SI), named after the Scottish engineer James Watt. The unit, defined as one joule per second, measures the rate of energy conversion or transfer. |