Birch & Willow has compiled three glossaries: Lamp and Luminary Design Glossary; Light Bulb Glossary; and Eco-Glossary. Our lighting business is an interdisciplinary undertaking. We hope the information provided in these glossaries will help you better understand the intersecting worlds of lighting design, technology and environmental responsibility where the development and creation of Birch & Willow products takes place. The glossaries include information from many sources as well as some of our own. Please contact us with any questions or suggestions
| Term |
| Definition |
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| A-Lamps (General Service Bulbs) |
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The standard incandescent bulb for most common uses. |
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| Average rated life |
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The time expressed in hours that half of a given number of test lamps burnt out in. The life span of individual bulbs purchased will almost always be slightly above or below this time. |
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| Amperes |
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Typically referred to as amps. A measure of electrical current. In incandescent lamps, the current is related to voltage and power as follows: Watts (power) = Volts x Amps (current). |
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| Ballast |
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A ballast transforms electrical energy used to provide current for the start up of fluorescent, mercury, metal halide, and low and high pressure lamps, and then control the current to regulate their operation. |
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| Base of socket |
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The socket is the receptacle connected to the electrical supply; the base is the end of the lamp that fits into the socket. There are many types of bases used in lamps, screw bases being the most common for incandescent and HID lamps, while bi-pin bases are common for linear fluorescent lamps. The lamp base mechanically holds the lamp in place in the application. The lamp base directly or indirectly (via a cable or lead-in wires) conducts electricity from the circuit to the lamp and can be designed to dissipate heat. Lamp bases should be operated within specified temperature range. |
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| Bayonet Base |
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A style of bulb base that uses keyways or bi-pins instead of threads to connect the bulb to the fixture base. The bulb is locked in place by pushing it down and turning it clockwise. |
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| Bulb |
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The everyday term for an incandescent lamp. Bulb refers to the outer glass bulb containing the light source. The lighting industry technical term is lamp. |
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| Bulb Size and Shape |
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Bulbs or lamps are marked with the shape followed by the size. The maximum diameter of the bulb is noted in eighths of an inch. Compact Fluorescent bulbs are "S", "D", "T", or "Q" shapes (denoting single, double, triple and quad sizes.) The code also includes a reference such as T4 to represent the size of the tube. |
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| Color rendering index (CRI) |
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An international system used to measure the effect a light source has to render the color of objects and surfaces. High CRI lights make virtually all colors look natural and vibrant which helps objects and persons illuminated to appear more true to life.. Low CRI causes some colors to appear washed out or even to take on a completely different hue. |
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| Color Temperature |
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The appearance of white light in terms of warmth or coolness. Yellowish-white ("warm") sources, like incandescent lamps, have lower color temperatures in the 2700K-3000K range; white and bluish-white ("cool") sources, such as cool white (4100K) and natural daylight (6000K), have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will appear. |
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| Compact fluorescent lamps (CFL) |
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The general term applied to fluorescent lamps that are single-ended and have small diameter tubes that can be bent to form a compact shape. This allows production of a wide variety of configurations, increasing the applications for fluorescent lighting and offering innovative energy efficient lighting solutions. Some CFLs have integral ballasts and medium or candelabra screw bases for easy replacement of incandescent lamps The CFL bulbs can be used as an alternative to incandescent bulbs. |
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| Cool White |
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A general term used to denote a color temperature of around 4100 K. The Cool White (CW) designation is used specifically for T12 and other fluorescent bulbs. |
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| Correlated Color temperature (CCT) |
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This specifies the color that a given bulb appears when it is in use. (Whether it looks ‘hot’ ‘warm’ or ‘cold’). It is compared in degrees Kelvin (K), to a source of reference at a given temperature. |
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| Decorative Bulbs (D) |
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Light bulbs that come in many assorted and unusual shapes; and are different in appearance from the standard A-lamps. |
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| Filament |
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A wire coil made of tungsten that produces light when heated by an electric current. Lamp filaments are offered in a variety of designs optimized for specific applications.
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| Fluorescent lamp |
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A high efficiency lamp that uses an electric discharge through low-pressure mercury vapor to produce ultra-violet (UV) energy. A fluorescent lamp has no filament running through it. Instead, cathodes (coiled tungsten filaments coated with an electron-emitting substance) at each end send current through mercury vapors sealed in the tube. Ultraviolet radiation is produced as electrons from the cathodes knock mercury electrons out of their natural orbit. |
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| Foot-Candle |
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This is the common measurement of the total light reaching a surface (level of light) used in the United States. One foot-candle is one lumen on one square-foot of a surface. |
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| G-Lamp |
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Globular shaped light bulbs.
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| GU-24 Bulbs/Sockets |
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The GU-24 socket and base system is designed to replace the Edison socket and base in energy efficient lighting fixtures. The GU-24 Light Bulb does not have the usual screw base, but instead has two bayonets protruding from the base (bi-pins). These insert into matching holes in the fixture's socket, and twist to lock into place. Twist and pull and the bulb come right out of the socket. |
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| Luminance |
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The luminous power incident per unit area of a surface. One lumen per square meter is one lux. One lumen per square foot is one foot-candle. |
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| Incandescent lamps |
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Light produced by the electrical heating of a material. |
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| Candela/ candlepower (cd) |
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The unit of measure indicating the luminous intensity (candlepower) of a light source in a specific direction; any given light source will have much different intensity, depending upon the direction considered. |
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| Kelvin |
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A measure of color temperature. |
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| Kilowatt |
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A measure of electrical usage. One thousand watts of electrical usage is equivalent to one kilowatt. |
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| Lamp |
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The terms lamp and bulb are often used interchangeably. Lamp is the lighting industry technical term for the commonly used term light bulb. A lamp is a glass enclosure containing gas or a filament or coating that glows when a contact is made with a source of electricity. |
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| Lamping |
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A technical term referring to the designer or manufacturer recommended wattage and lamp bulb type for a specific lamp or fixture or lighting application. |
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| LCL (Light Center Length) |
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The length, usually in inches, from a given point on the base of a lamp to its light center. |
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| LED |
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A light-emitting diode is a semiconductor diode that emits incoherent narrow-spectrum light. A LED is usually a small area light source, often with optics added to the chip to shape its radiation pattern and assist in reflection. |
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| Lumens |
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The actual quantity of light produced by a lamp or other source. A unit of luminous flux; overall light output; quantity of light, expressed in lumens. It is expressed as the rate light falls on one square foot of surface area from a distance of one foot from the light source to the surface. |
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| Luminous Flux |
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The amount of light flowing over a given area in a period of time.
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| Lux |
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The international standard unit for measuring light levels (as oppose to Foot-Candle in the U.S.A). It is one lumen per square meter. |
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| Maximum overall length (MOL) |
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The total length of a lamp, from top of bulb to bottom of base, typically expressed in inches. |
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| PAR Lamps |
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This stands for Parabolic Aluminized Reflector. These are extremely bright bulbs that can be used for the accurate controlling of light levels. Since the parabola shaped reflector is excellent at reflecting and focusing all the light produced in a beam in a chosen direction. |
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| R Lamp or Reflector Lamps |
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Reflector lamps are made of ‘soft’ glass as oppose to the ‘hard’ glass of a PAR lamp. This distinction concerns the glass structure and ability to deal with higher temperatures. They also differ in usually having their reflector source as an aluminum or silvery coating on the bulb itself. |
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| T-Lamps |
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A lamp that is tubular in shape. |
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| Transformer |
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A device used in CFL and other low voltage lamps to raise or lower electrical voltage. |
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| Types of Bulbs |
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A letter or letters are used to designate the shape of bulbs. A number is used to indicate the bulb size. In the United States, light bulbs are measured in eighths of an inch around their maximum diameter. |
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| U-Lamp |
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A fluorescent lamp with two ends that is shaped like the letter ‘u’. |
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| Voltage |
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A measurement of the pressure of electricity going through a wire. |
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| Watt |
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A unit of electrical power. Lamps are rated in watts to indicate power consumption. |
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