Light+Vocabulary

 a light source containing an arc (see above). Also called a discharge lamp, or an arc discharge lamp. Candlepower Distribution Curve: a graphical presentation of the distribution of light intensity of a light source, usually a reflector lamp or luminaire. **Eccentricity (Maximum):** in High Intensity Discharge lamps the Bulb to Arc Angle is the angle oof of center between electrodes and bulb. The Bulb to Base Angle is the angle oof of center that the bulb is from the base. **Efficacy:** a measurement of how effective the light source is in converting electricla energy to lumens of visible light. Expressed in lumens-per-watt this measure gives more weight to the yellow region of the spectrum and less weight to the blue and red region where the eye is not as sensitive. **Electromagnetic Ballast:** a ballast used with discharge lamps that consists primarily of transformer-like copper windings on a steel or iron core. **Field Angle:** the angular dimension of the cone of light from reflectorized lamps encompassing the central part of the beam out to the angle where the intensity is 10% of maximum. **Filament:** metal tungsten wire heated by the passage of electrical current, used to emit light in incandescent lamps. In fluorescent lamps the filament is coated with emission mix and emits electrons when heated. **Flicker:** the period variation in light level caused by AC operation that can lead to strobe effects. **Flood:** used to refer to the beam pattern of a reflector lamp, which disperses the light over a wide beam angle, typically 20 degrees or more. **Floodlight:** a luminaire used to light a scene or object to a level much brighter than its surroundings. Usually floodlights can be aimed at the object or area of interest. **Glare:** visual discomfort caused by excessive brightness is called discomfort glare. If task performance is affected it is called disability glare. Glare con be direct or indirect. **Harmonic:** an integral multiple of the fundamental frequency that becomes a component of the current. **Harmonic Distortion:** distortion of an AC waveform caused by multiples of the fundamental frequency. Odd triplet harmonics may result in large currents on the neutral line in a four-wire Wye three-phase system. **High-Bay Lighting:** lighting designed for industrial locations with a ceiling height of 35 feet and above. High Efficiency (Energy Saving) Electromagnetic Ballast: ballast with core & coils,designed to minimize ballast losses compared to the "standard" ballast. **Integral:** a popular term for a compact fluorescent lamp which includes a built-in ballast. **Inverse Square Law:** formula stating that if you double the distance from the light source, the light goes down by a factor of 4, if you triple the distance, it goes down by a factor of 9, and so on. <span style="font-family: Arial,Helvetica,sans-serif;">**Light Loss Factor:** the product of all factors that contribute to lowering the illumination level including reflector degradation, dirt, lamp depreciation over time, voltage fluctuations, etc. <span style="font-family: Arial,Helvetica,sans-serif;">mercury and High Pressure Sodium lamps may be operated in any burn position and will still maintain their rated performance specifications. Metal Halide and Low Pressure Sodium lamps, however, are optimized for performance in specific burn positions, or may be restricted to certain burn positions for safety reasons. <span style="font-family: Arial,Helvetica,sans-serif;">this measurement accounts for the fact that of the two light sensors in the retina, rods are more sensitive to blue light (scotopic vision) and cones to yellow light (photopic vision). The scotopic/photopic (S/P) ratio is an attempt to capture the relative strengths of these two responses. S/P is calculated as the ration of scotopic lumens to photopic lumens for the light source on an ANSI reference ballast. Cooler sources (higher color temperatures lamps) tend to have higher values of the S/P ratio compared to warm sources. <span style="font-family: Arial,Helvetica,sans-serif;">**Seal Temperature (Maximum):** the maximum operating temperature of the seal of the lamp in Celsius. <span style="font-family: Arial,Helvetica,sans-serif;">**Spot:** a colloquial term referring to a reflector lamp with a tight beam of light, typically around 10 degrees or less. It comes from the fact that such a lamp produces a narrow spot of light as opposed to a wide flood of light. <span style="font-family: Arial,Helvetica,sans-serif;">**Task Lighting:** supplemental lighting provided to assist in performing a localized task, e.g. a table lamp for reading or an inspection lamp for fabric inspection. <span style="font-family: Arial,Helvetica,sans-serif;">**Ultra:** a common way of referring to high efficiency GE T8 family of lamps that perform better than standard T8 lamps. Also refers to the system. <span style="font-family: Arial,Helvetica,sans-serif;">**Valance Lighting:** lighting from light sources on a wall typically above eye level, shielded by horizontal panels. The light may be upward or downward directed. <span style="font-family: Arial,Helvetica,sans-serif;">**Veiling Reflection:** effective reduction in contrast between task and its background caused by the reflection of light rays; sometimes called "reflected glare." You might have dealt with veiling reflections when you have to tilt a shiny magazine to avoid glare so as to read it, or struggled with reading a computer monitor because of the reflection of a window or a light fixture. <span style="font-family: Arial,Helvetica,sans-serif;">**Visual Task:** the task associated with seeing; objects and details that must be seen to perform an activity. <span style="font-family: Arial,Helvetica,sans-serif;">**Warm White:** refers to a color temperature around 3000K, providing a yellowish-white light. <span style="font-family: Arial,Helvetica,sans-serif;">**Wattage Indicator Reduced:** indicates that this is a reduced wattage option for lamps normally used in this application. Be sure to check wattage, lumens and life to determine which lamp is best suited to your needs. <span style="font-family: Arial,Helvetica,sans-serif;">**Wavelength:** the distance between two neighboring crests of a traveling wave. The wavelength of light is between 400 and 700 nanometers.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Arc Lamp: **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Arc Length: **<span style="font-family: Arial,Helvetica,sans-serif;">in High Intensity Discharge lamps this is the distance between the electrode tips, which represents the physical length of the electrical discharge.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Baffle: **<span style="font-family: Arial,Helvetica,sans-serif;">in lighting this is usually a grooved surface that deflects and controls the “flow” of light to soften it and minimize reflected glare. Baffle trims (sometimes called step baffle trims or stepped baffle trims), made of plastic or metal, are often integral parts of recessed downlights. They are often colored a flat black to absorb some of the light but can have other finishes such as flat white, brushed copper, or brushed nickel.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Ballast: **<span style="font-family: Arial,Helvetica,sans-serif;">an auxiliary piece of equipment required to start and to properly control the flow of current to gas discharge light sources such as fluorescent and high intensity discharge (HID) lamps. Typically, magnetic ballasts (also called electromagnetic ballasts) contain copper windings on an iron core while electronic ballasts are smaller and more efficient and contain electronic components.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Bayonet: **<span style="font-family: Arial,Helvetica,sans-serif;">a style of bulb base which uses keyways 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.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Beam Angle: **<span style="font-family: Arial,Helvetica,sans-serif;"> the angular dimension of the cone of light from reflectorized lamps encompassing the central part of the beam out to the angle where the intensity is 50% of maximun. The beam angle sometimes called "beam spread" is often part of the ordering code for the reflectorized lamps.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Beam Lumens: **<span style="font-family: Arial,Helvetica,sans-serif;">the total lumens present within the portion of the beam contained in the beam angle.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Black Light: **<span style="font-family: Arial,Helvetica,sans-serif;"> a popular term referring to a light source emitting mostly mear UV (320 to 400 nm) and very little visible light.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Bulb: **<span style="font-family: Arial,Helvetica,sans-serif;">a loose way of referring to a lamp. The outer glass bulb containing the light source.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Bulb Material or Coating: **<span style="font-family: Arial,Helvetica,sans-serif;"> the type of glass used in the glass envelope surrounding the light source. The material can also have coatings applied to achieve particular performances.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Candlepower: **<span style="font-family: Arial,Helvetica,sans-serif;">initial mean spherical candlepower at the design voltage. Mean spherical candlepower is the generally accepted method of rating the total light output of miniature lamps. To convert this rating to lumens, multiply it by 12.57.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Cathode: **<span style="font-family: Arial,Helvetica,sans-serif;">metal filaments that emit electrons in a fluorescent lamp. Negatively charged free electrons emitted by the cathode are attracted to the positive electrode (anode), creating an electric current between the electrodes.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Cathode Resistance: **<span style="font-family: Arial,Helvetica,sans-serif;">resistance of the cathode in a fluorescent lamp. It is measured "cold" before the lamp is turned on (Rc) or "hot" after the lamp is turned on (Rh). The ratio of the hot resistance to the cold resistance is also measured (Rh/Rc).
 * <span style="font-family: Arial,Helvetica,sans-serif;">Coil: **<span style="font-family: Arial,Helvetica,sans-serif;">windings of copper or aluminum wire surrounding the steel core in ballast. Also refers to the entire assembly comprising the inductor or transformer.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Color Rendering Indicator: **<span style="font-family: Arial,Helvetica,sans-serif;"> draws attention to the fact that this is a lamp with high color rendering, which helps objects and persons illuminated to appear more true to life. A number indicating the degree of "yellowness" or "blueness" of a white light source. Measured in kelvins, CCT represents the temperature an incandescent object (unlike filament) must reach to mimic the color of the lamp. 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 and natural daylight, have higher color temperatures. The higher the color temperature the whiter, or bluer, the light will be.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Core: **<span style="font-family: Arial,Helvetica,sans-serif;">component of electromagnetic ballast that is surrounded by the coil. Core is comprised of steel laminations or solid ferrite material
 * <span style="font-family: Arial,Helvetica,sans-serif;">Daylight Lamp: **<span style="font-family: Arial,Helvetica,sans-serif;">a lamp resembling the color of daylight, typically with a color temperature of 5500K to 6500K.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Diamond Precise: **<span style="font-family: Arial,Helvetica,sans-serif;"> is the GE trade name for its line-voltage MR16 halogen lamp.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Dichroic reflector: **<span style="font-family: Arial,Helvetica,sans-serif;"> a reflector or filter that reflects one region of the spectrum while allowing the other region to pass though. A reflector lamp with a dichroic reflector will have a "cool beam", most of the heat has been removed from the beam by allowing it to pass though the reflector while the light has been reflected.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Light Pollution: **<span style="font-family: Arial,Helvetica,sans-serif;">light that is directed to areas where it is not needed, and thereby interferes with some visual act. Light pollution directed or reflected into the sky creates a "dome" of wasted light and makes it difficult to see stars above cities.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Light Trespass (Spill Light): **<span style="font-family: Arial,Helvetica,sans-serif;"> light that is not aimed properly or shielded effectively can spill out at into areas that don't want it: it can be directed towards drivers, pedestrians or neighbors. It is distracting and annoying and can sometimes be disabling.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Lumens: **<span style="font-family: Arial,Helvetica,sans-serif;">ameasure of the luminous flux or quantity of light emitted by a source. For example, a dinner candle provides about 12 lumens. A 60-watt Soft White incandescent lamp provides about 840 lumens.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Maximum Overall Length (M.O.L.): **<span style="font-family: Arial,Helvetica,sans-serif;">the end-to-end measurement of a lamp, expressed in inches or millimeters.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Medium Base: **<span style="font-family: Arial,Helvetica,sans-serif;">usually refers to the screw base typically used in household incandescent lamps. There is also the medium bipin base commonly used in T12 and T8 fluorescent lamps.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Monochromatic Light: **<span style="font-family: Arial,Helvetica,sans-serif;">light with only one wavelength (i.e. color) present.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Mounting Height: **<span style="font-family: Arial,Helvetica,sans-serif;">distance from the bottom of the fixture to either the floor or work plane, depending on usage.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Operating Position or Burn Position: **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Parallel Lamp Operation: **<span style="font-family: Arial,Helvetica,sans-serif;">refers to ballasts that employ multiple output current paths from a single ballast to allow lamps to operate independent of one another, allowing other lamps operated by the ballast to remain lit should companion lamp(s) fail.
 * <span style="font-family: Arial,Helvetica,sans-serif;">PAR Lamp: **<span style="font-family: Arial,Helvetica,sans-serif;">PAR is an acronym for parabolic aluminized reflector. A PAR lamp, which may utilize either an incandescent filament, a halogen filament tube or a HID arc tube, is a precision pressed-glass reflector lamp. PAR lamps rely on both the internal reflector and prisms in the lens for control of the light beam.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Photopic: **<span style="font-family: Arial,Helvetica,sans-serif;">vision for which the cones in the eye are responsible; typically at high brightness and in the foveal or central region.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Power Factor: **<span style="font-family: Arial,Helvetica,sans-serif;">measurement of the relationship between the AC source voltage and current. High power factor ballasts require less AC operating current at the same wattage than an equivalent low power factor ballast.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Preheat Circuit: **<span style="font-family: Arial,Helvetica,sans-serif;">a type of fluorescent lamp-ballast circuit used with the first commercial fluorescent lamp products. A push button or automatic switch is used to preheat the lamp cathodes to a glow state. Starting the lamp can then be accomplished using simple "choke" or reactor ballasts.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Quartz: **<span style="font-family: Arial,Helvetica,sans-serif;">a name for fused silica or melted sand from which many high-temperature containers are fashioned in the lighting industry. Quartz looks like glass but can withstand the high temperatures needed to contain high intensity arc discharges.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Scotopic: **<span style="font-family: Arial,Helvetica,sans-serif;">vision where the rods of the retina are exclusively responsible for seeing, typically like the light levels in the countryside on a moonless, starlit night.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Scotopic/Photopic (S/P) Ratio: **