Ch 19 Lighting Flashcards
Candlepower (cp)
unit of luminous intensity approximately equal to the horizontal light output from a candle
Lumen (lm)
unit of luminous flux equal to the flux in a unit solid angle of one steradian from a uniform point source of 1 candlepower (cp)
Illuminance
the density of luminous flux incident on a surface in lumens per unit area
Luminance
the luminous flux per unit of projected area and unit solid angle leaving a surface, either reflected or transmitted - measurable state of object luminosity
Candela
measures luminance or brightness
Footlambert
measures luminance of brightness
Brightness
like luminance, but measures the physiological sensation of the adaptation of the eye
Direct Glare
when a light source in the field of vision causes discomfort and interference with the visual task - causes by brightness of source, position, background illumination, and adaptation of eye to environment
Visual Comfort Porbability (VCP) Factor
developed to evaluate direct glare by figuring the percentage of people who find a situation acceptable from a particular location and direction
Critical Zone for Direct Glare
the area above a 45 degree angle from the light source
Reflected Glare
occurs when a light source is reflected from a viewed surface into the eye causing a decrease in contrast between the task and its background
Veiling Reflection
when reflected glare interferes with the viewing task caused by a interaction of light sources and can often be remedied by providing general lighting with task lighting that is flexible
Contrast
difference in illumination level between one point and nearby points
Immediate Surroundings Brightness Ratio
3:01
Nearby General Brightness Ratio
5:01
Remote Surroundings Brightness Ratio
10:01
Uniformity
makes a space feel comfortable and pleasant, but can become monotonous and complete uniformity is not always desired for specific tasks
Color of Lighting
an interaction between the color of the light source and the color of the objects that reflect the light
Efficacy
measure of energy efficiency that looks at the ratio of luminous flux emitted to the total power input of the source measured in lumens/watt
Incandescent - Benefits
inexpensive, compact, easy to dim, can be repeatedly restarted without decrease in lamp life, can be easily controlled with reflectors and lenses, and have a warm color rendition
Incandescents - Negatives
low efficacy, short lamp life, and high heat output - not suitable for large, energy efficient installations
Reflector Lamp - Incandescent
has a wide beam spread - (R)
Elliptical Reflector - Incandescent
produces an efficient through of light from a fixture by focusing the light beam at a point slightly in front of the lamp before it spreads out - smaller spread than an R (reflector) lamp - (ER)
Parabolic Aluminized Reflector - Incandescent
focuses light in a narrow spread, with the light rays more parallel because its reflector is a parabola - available in “flood” and “spotlights” - (PAR)
MR-16 - Incandescent
low-voltage, multifaceted mirror reflector with several angle of beam spreads - narrowest beam spread of incandescent
Tungsten-Halogen - Incandescent
increased lamp life due to recurring cycle of tungsten filament, causes low lumen depreciation and more uniform light color, greater efficacy and more compact, but has higher operating temperature putting them more on the blue end of the spectrum
Fluorescent
have high efficacy, relatively low initial cost, long life, and variety of color temperatures – dimmable – best for general illumination due to less ability to easily control them
Measurement of Incandescent and Fluorescent Lamps
done in 1/8” of an inch increment so a 5/8” diameter fluorescent would be a T5 or a R-28 incandescent would be a 4.75” diameter lamp
GU-24 Lamp - Fluorescent
high-efficacy compact fluorescent with a 2-pin base - becoming the most common energy efficient lamp with a variety of color temperatures and a long lamp life - designed to replace the standard Edison screw base
High-Intensity Discharge (HID)
produce light by passing electric current through a gas or vapor under high pressure - all types require time to restart after power failure or being shut off
Mercury-Vapor Lamp (HID)
long lamp life, but poor color rendering and are usually limited to outdoor lighting and industrial applications like warehouses
Metal-Halide Lamp (HID)
has the best combination of HID lamps - with a color rendering between 60 - 90, high efficacy, and relatively long lamp life - but they have a large shift in color temperature over time
Ceramic Metal Halide (HID)
higher temperature to function which gives it an improved color rendering and light control, with better color consistency over lamp life, but it has a higher initial costs, difficult to dim - good for a retail space where long life and high efficacy are needed with point source control and excellent color rendition
High Pressure Sodium (HID)
one of the most efficient lamps available with 80 - 140 lm/W with a lamp life of 10,000 - 24,000 hours, but they produce a very yellow light
Light Emitting Diodes (LED)
very bright, long life (100,000 hours +), and low power consumption, produces no heat, can be controlled by a digital interface, but low efficacy and high costs
Direct Lighting
provides all the light output directly on the task
Semidirect Lighting
puts majority of light down, but puts a small percentage towards the ceiling - must be surface mounted
Direct-Indirect Lighting
distributes light up and down almost equally
Indirect Lighting
directs all the light toward a reflective ceiling where the light illuminates the room by reflectance
Task-Ambient Lighting
common in commercial lighting providing a general background illumination level with a separate light fixture at individual work stations - energy efficient and creates more positive work environment
Color Rendering Index
measure of how well a source renders color compared to the same object lighted with a referenced source of a CRI of 100
Common Office Kelvin Temperature
3,500
Color Temperature of Hazy Blue Sky
9000
Color Temperature of 60 W Incandescent
2790
Color Temperature of 150 W Incandescent
2800
Color Temperature of Tungsten-Halogen
3000
Color Temperature of Cool-White Fluorescent
4300
Color Temperature of Warm-White Fluorescent
3100
Color Temperature of Cool-White Deluxe Fluorescent
4100
Color Temperature of Daylight Fluorescent
6500
Color Temperature of Metal Halide HID
3600-4200
First Step of Lighting Design
determine function of space and require light levels (footcandles) to dictate lighting system type
Step Two of Lighting Design
determine character of space as it relates to lighting needs: uniformity, control of lighting, fixed versus portable luminaires, and visibility of light sources
Third Step of Lighting Design
select lamp type based on color rendition required, economy, control required and select luminaires to accompany lamps to control glare, be cost effective, and provide adjustability as needed
Fourth Step of Lighting Design
the location and number of luminaires are determined based on light level and tasks to be performed
Zonal Cavity Method
used for larger installations where the number and location is calculated using required footcandles and efficacy of the lamp, number of lamps, the coefficient of utilization of the luminaire, and lamp lumen depreciation factor, and conditions the lamp will be used in
Coefficient of Utilization (CU)
a number used to represent how efficient the luminiare distributes the light from the lamps under various degrees of finish reflectivity of the floor, walls, and ceiling
Emergency Lighting
is required for occupants to safely exit a building with means of egress illumination, exit signs, voice communication systems, smoke control systems, etc run on a backup generator or batteries required a 1 fc measured from the floor for a minimum of 90 minutes
Locations required by Codes for Emergency Lighting
exit access corridors and aisles in rooms with 2 or more exits, exit access corridors and stairways in buildings with 2 or more exits, and exit discharge elements, like a lobby, where 50% of the occupants may exit through
