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Definition
visually evaluated radiant energy.
white light is produced when a source emits approx. equal quantities of energy over the entire visible spectrum |
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Definition
| unit of luminous intensity approx. equal to the horizontal output from an ordinary wax candle. in the metric system, called the candela |
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Term
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Definition
| unit of luminous flux equal to the flux in a unit solid angle of one steradian from a uniform pint source of one candlepower. on a unit sphere )1-foot radius), an area of 1 square foot will subtend an angle of one steradian. |
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Definition
| density of luminous flux incident on a surface in lumens per unit area. one lumen uniformly incident on 1 sq. foot of area produces an illuminance of 1 footcandle. in si units, the measurement is lux. |
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Term
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Definition
luminous flux per unit of projected (apparent) area and unit solid angle leaving a surface, either reflected or transmitted.
by definition, si measurement, is the candela per square meter, also called the nit.
luminance takes into account the reflectance and transmittance properties of materials and the direction in which they are viewed.
100 lux, striking a 1 sq. meter surface with 50% reflectance, would result in 50 candelas per sq. meter.
luminance is sometimes called brightness, although brightness includes the physiological sensation of the adaptation of the eye, wheras luminance is the measurable state of object luminosity |
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Definition
| solid angular flux density in a given direction measured in candlepower or candelas. |
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| variables involved with lighting |
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Definition
| nature of the task itself, age of the person performing the task, reflectances of the room, and the demand for speed and accuracy in performing the task. |
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| various areas and activities are assigned an illuninance category from A to I |
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Definition
| A represents the lowest values for general lighting in noncritical areas, and I represents requirements for specialized and difficult visual tasks. |
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Definition
1) direct glare-results when a light source in the field of vision causes discomfort and interference with the visual task. extent of the problem depends on the brightness of the source, its position, background illumination, and adaptation of the eye to the environment. to evaluate direct glare, the VCP factor was developed (visual comfort probability). factor is the percentage of people, who, when viewing from a specified location and in a specified direction, will find the situation acceptable in terms of discomfort glare. for most situations, the critical zone is in the area above a 45-degree angle from the light source.
many direct glare problems can be solved by using a luminaire with a 45-degree cutoff angle or by moving the luminaire out of the offending field of view. |
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Definition
occurs when a light source is reflected from a viewed surface into the eye. if it interferes with the viewing task, it is also called veiling reflection.
ie.-strong light on paper with pencil writing can bounce off the relatively reflective graphite, mkaing it almost as bright as the paper, and effectively obliterate the writing. |
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Definition
are a complex interaction of light source and brightness, position of the task, reflectivity of the task, and the position of the eye.
one of the simplest solutions is to move the position of the task or the light source. easy to calculate, because, for light, the angle of teh incidence is equal to the angle of reflection. |
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| difference in the illumination level between one point and nearby points. |
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Definition
should be limited to 3:1 between the task adn immediate surroundings.
uniformity of lighting affects a person's perception of space as being comfortable and pleasant to be in.
color in lighting is an interaction between the color of the light source adn the color of the objects that reflect the light. |
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Term
| three types of light sources in addition to natural light |
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Definition
1. incandescent
2. flourescent
3. high-intensity discharge |
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Term
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Definition
| ratio of luminous flux emitted to the total power input of the source and is measured in lumens per watt. important measure of the energy efficiency of a light source. |
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Definition
consists of a tungsten filament placed within a sealed bulb containing an inert gas. when electricity flows throught the lamp, the filament grows, producing light.
designated by their shpare followed by a number that indicates the diameter in eigths of an inch at the widest point. Thus, an R-38 is a reflector lamp with a diameter of 4 3/4" (38/8") |
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Term
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Definition
* R lamp-standard reflector lamp and has a wide beam spread.
* ER, or elliptical reflector, provides a more efficient throw of light from a fixture by focusing the light beam at a point slightly in front of the lamp before it spreads out. spread is slightly smaller than the R lamp.
* PAR-parabolic aluminized reflector, focuses the light in a tighter spread with the light rays more parallel because its reflector is a parabola with the filament at the focus at the parabola. available (as well as the R), in flood spreads and spotlights.
* MR-16-low-voltage, multi-faceted mirror reflector. several angles of beam spread are available, from a very narrow spot, to a medium-wide spread. Generally have the narrowest beam spread of the four lamp types, next being the PAR.
incandescents are inexpensive, compact, easy to dim, can be repeatedly started without a decrease in lamp life, and have a warm color rendition. their light output can easily be controlled with reflectors and or lenses.
disadvantages: low efficacy, short lamp life, hight heat output. makes them undesirable for large, energy-efficient installations. |
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Term
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Definition
type of incandescent lamp.
light is produced by the incandescence of the filiment, but there is a small amount of halogen, such as iodine or bromine, in the bulb, with the inert gas. part of the tungsten filament is burned off as the lamp operates, but it mixes with the halogen and is redeposited on the filament instead of on the wall of the bulb. results in longer lamp life, low lumen depreciation over time, and more uniform light color.
because it burns under high pressure and temperature, bulb is made from quartz, adn much smaller than a standard incandescent. often referred to as a quartz-halogen.
in addition, greater efficacy rate than standar incandescents, compact, & higher operating temperature give more light in the blue end of the spectrum, resulting in a light that looks whiter.
also, becuase at such high temps, high explosive rate, so inclosed in another bulb or are covered with a piece of glass or a screen. |
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Term
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Definition
another class of incandescent.
operate at a lower voltage than 120 volts, usually 12 volts. however, they operate at higher current, so their filaments have to be thicker to carry the added current. because of this, they are also more compact, resulting in smaller lamps adn lamps with better beam control.
often used where small luminaries are required or where narrow beam spreads are needed. narrow beam spread makes low-voltage lamps energy efficient when lighting small objects or larger objects at a distance. main disadvantage is a transformer is required to step down the line voltage. resulting in bulkier luminaire and higher initial cost. |
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Term
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Definition
| contain a mixture of an inert gas adn low-pressure mercury vapor. when lamp is energized, mercury arc is formed that creates ultraviolet light. |
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Term
| three types of flourescent light |
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Definition
1. preheat-lamps which have been supplanted by rapid start types
2. rapid start
3. instant start
all flourescent lamps have a ballast, which supplies the proper starting and operating voltages to the lamp as well as limiting the current |
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Term
| flourescent lamps are designated according to: |
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Definition
their type, wattage, diameter, color, and type of starting circuitry.
*An F40T12WW/RS describes a flourescent lamp, 40 watts, tubular, 12/8 of an inch in diameter (1 1/2"),warm white color, with a rapid start circuit.
size is designated in eitgths of an inch.
variety of lengths, 4' being most common. Lengths of 2, 3, and 8' also available. |
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Term
| standard flourescent lamps have: |
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Definition
high efficacy, relatively low initial cost adn long life, and are available in a variety of color temperatures. They can also be dimmed, although flourescent dimmers are more expensive.
because larger than incandescent, more difficult to control them precisely, so they are usually more suitable for general illumination.
many standard T12's are being replaced by smaller and lower wattage T8 & T5, and incandescent lamps are being replaced by compact flourescent lamps.
primary advantage to both is the energy savings realized by getting the same light level for less power input. |
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| T8 & T5 are becoming more popular |
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Definition
| because of their higher efficacy rate, better color rendition, as well as the smaller diameter lamps make it possible to design smaller luminaires and more efficiently control the light. |
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Term
| compact flourescent lamps |
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Definition
(CF) consist of T4 or T5 tubes bent in a U shape with the pins in one end of the lamp.
various configurations, using 2, 3, or 4 bends.
in addition to energy savings, they have a much longer life than the standard incandescent lamps they can replace. |
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Term
| High intensity discharge (HID) lamps |
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Definition
| produce light by passing an electric current through a gas or vapor under high pressure. include mercury vapor, metal-halide, and high-pressure sodium. |
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Term
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Definition
electric arc is passed through high-pressure mercury vapor, which causes the lamp to produce both ultraviolet light, and visible light, primarily in the blue-green spectra band.
have long lamp life but poor color rendering. generally limited to outdoor lighting and industrial applications such as warehouses. |
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Term
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Definition
similar to mercury vapor, except that halides of metals are added to the arc tube. this increases efficacy and improves color rendition. relatively long life.
main disadvantage is they experience a large shift in apparent color temperatures over their life.
Like all HID lamps, have an outer bulb to protect arc tube and to protect people from dangerous uv light.
three types of outer bulbs
1. clear-used when optical control is required
2. phosphor-coated-better for color renditions
3. diffuse-specified in recessed downlight fixtures installed in low ceilings. |
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Term
| high pressure sodium (HPS) lamps |
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Definition
produce light by passing an electric arc through hot sodium vapor.
arc tube must be made of a special ceramic material to resist attack by hot sodium.
most effficient lamps available, extremely long life
unfortunately, produce a very yellow light. is possible for some interior applications, with color rendition. |
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Term
| HID lamps provide many advantages, however... |
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Definition
| they all require time to restart after being shut off or in case of a power failure. lamp must first cool adn then it takes time to warm up. |
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Term
| in addition to the three basic types of lamps there are neon and cold-cathode lamps |
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Definition
neon-can be formed into an unlimted number of shapes and are used for sign and specialty accent lighting. variety of colors.
cold-cathode-similar to neon in that they can produce in long runs of thin tubing bent to shape, but they have a higher efficacy, slightly larger, can produce several shades of white as well as many colors. |
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| types of lighting systems |
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Definition
1. direct
2. semidirect
3. indirect |
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Term
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Definition
| provide all light output on the task. ie. a recessed flourescent luminaire. |
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Term
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Definition
| put a majority of the light down and a small portion on the ceiling. obviously, must be surface mounted or suspended. |
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Definition
| distribute light up and down about equally. |
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Term
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Definition
| direct all light toward a reflective ceiling where the light illuminates the room by reflection. |
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Term
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Definition
common commercial lighting system. provides back-ground illumination level with separate light fixtures used at an individual workstations or wherever it is needed.
done with desk lamps or directed spotlights, or by locating more fixtures near the tasks requiring more illumination.
energy-efficient, respond to individual lighting needs, and create more pleasant work environments. |
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Term
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Definition
among most commonly used.
luminaire is directly attached to the finished surface of the ceiling, directing all or a majority of the light into the space.
used where there is not sufficient space above the ceiling to recess a fixture or where fixtures are added after the ceiling has been constructed.
include incandescent, flourescent, or HID lights, as well as various track. |
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Term
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Definition
residential recessed is usually limited to incandescent downlights because they can be located in limited space or between floor or ceiling joists.
commercial-when entire ceiling is made up of lighting, a luminous ceiling is formed.
can be general downlights for overall illumination or wallwashers, which direct light in one direction only. |
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Term
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Definition
luminaires dropped below the level of the ceiling. can include direct incandescent or flourescent, track lighting, indirect systems, chandeliers, and other types of specialty lights.
suspended is required for indirect lighting systems. fixture must be located far enough below the ceiling to allow for the proper spread of light to bounce off the surface. |
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Term
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Definition
| can provide direct, indirect, direct-indirect. sconces most direct toward the ceiling. |
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Definition
| common with taks-ambient systems. individual lights are built into the furniture above the worksurface to provide sufficient task illumination, while uplighting is provided by lights either built into the upper portion of the furniture or as freestanding elements. |
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Definition
most common-floor lamps
freestanding lights that direct most of their output to the ceiling are called torcheres. |
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Definition
| includes table lights, reading lamps, and fixtures that are intended for strictly decorative lighting rather than for task or ambient. |
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Definition
color of any object we see is dependent on both the color of the object as well as the color of the light striking it.
ie. incandescent light striking a blue object will tend to grey out the object, while the object will be enhanced if viewed under daylight. |
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Term
| spectral energy distribution |
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Definition
measure of the energy output at different wavelengths, or colors.
light sources are given a single number rating of their dominant color based on the temperature in degrees Kelvin to which a blackbody radiator would have to be heated to produce color.
technically, only incandescent sources can have a color temperature designation, buan an apparent color temperature is often used to describe the degree of whiteness of flourescent lamps and outher sources. |
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Term
| the lower the color temperature |
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Definition
the warmer the light
as temperature increases, the light becomes more blue and white |
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Term
| color rendering index (CRI) |
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Definition
measure of how well one source renders the color of an object when compared with the same object lighted with a reference source of similar chromaticity whose CRI is 100.
index is a number between 1 and 100, many cases, the reference source closely resembles a common incandescent lamp.
most interior applications, color temp ranges from 2700 K to 5000K.
most office 3500K |
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Term
| using a lamp with a high compliment of blue and violet will |
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Definition
| make finishes and furniture with warmer colors appear dull, gray, and washed out. |
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Term
| first step in lighting design |
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Definition
determine the function of teh space and the visual task to be performed.
determining light levels, whether the space will be single or multiple use, special conditions that might dictate a particular kind of lighting solution.
existing conditions such as daylight distribution, ceiling height, ceiling construction, size of the room, and other physcial limitations. |
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Term
| additional considerations |
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Definition
degree of uniformity of lighting, light control, fixed lighting versus portable lamps, and the visibility of light sources.
lamp type selection is based on color rendition required, overall economy, type of control required. |
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Term
| concurrent with lamp selection |
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Definition
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Term
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Definition
number and location of luminaires.
for larger installs, number and location should be calc'd according to the zonal cavity method developed by the IES. which, determines number of luminaires required to provide a given footcandle level by using efficacy of the lamp, number of lamps in teh luminaire, and coefficient of utilization of teh luminaire, gradual loss of light output of the lamps over time (lamp lumen depreciation factor), conditions, which affects the amount of dirt collected on the lamps over time. |
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Term
| Coefficient of Utilization (CU) |
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Definition
| number used in these calcs that represents how efficiently teh luminaire distributes the light from the lamps under various degrees of finish refelctivity of the floor, walls, and ceiling. |
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Term
| providing number of fixtures to provide a certain footcandle level isn't enough |
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Definition
| add lighting may be required to minimize dark wall surfaces, to highlight certain areas, and to provide interest and contrast to the overall design. |
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Term
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Definition
technical drawing located in the same orientation as teh floor plan and drawn at the same scale.
in add to showing construction of ceiling adn location of air diffusers, smoke detectors, adn other objects in the ceiling, it shows the location of all the built-in lighting. switching may also be shown.
larger projects, designer may develop rcp with only luminaire locations, while electrical engineer consult develops a lighting plan that includes switching and circuiting. |
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Term
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Definition
designer should decide how lights in a space should be switched.
based on function of lighting, how muc individual control is required, where the switches would best be located, energy conservation needs, and maximum electrical load requirements on any one circuit. |
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Term
| circuiting of lights also dependent on |
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Definition
type of control required.
many lights connected to a dimmer switch must be on their own circuit.
both incan. and flour. can be dimmed, but flour. dimmers are more expensive adn special fixtures are required to minimize flicker as they are dimmed. |
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Term
| incand. should be on a circuit separate from |
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Definition
flourescent. often mandatory in commercial b/c incandescent are on 120 volt circuits adn flour are on 277 volt circuits.
277 volt are more efficient. |
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Term
| lights can also be switched by |
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Definition
| low-voltage relay switching, automatic time clocks, and by proximity devices that sense when people enter or leave a room |
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Term
| number of switches also depends on |
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Definition
electrical load limitations.
determined by the electrical engineer consult.
electrical building codes limit total wattage that can be connected to any one circuit, so a large space with a great deal of light will have several switches. |
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Term
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Definition
| vertically glazed area placed between two different roof levels to admit light. |
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| help minimize energy costs |
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Definition
using daylight as much as possible, selecting high-efficacy lamps, using efficient luminaires, minimizing unneeded ambient illumination, providing task lighting only where it is needed, and selecting high-reflectance ceiling, wall, and floor surfaces to reduce the number of fixtures required to light a space.
also, auto switching and return air luminaires, auto switching shuts off lights in an unoccupied room, and return air fixtures move exhaust air over the lamps, keeping them cooler and helping them operate more efficiently. |
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Term
| emegency lighting is required |
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Definition
exit stairs and corridors as well as in certain occupancies such as places of assembly, educational facilities, hazardous locations, and other places where occupancy loads exceed a given number.
must be an exit sign at each door, each door leading to an exitway, and directional exit sighns at corridor intersections or where a corridor changes direction so that it is always evident to teh occupants where the exits are |
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