PDX_23_Lighting Vocabulary Flashcards
The direct light that falls on a service
Incident light
Electromagnetic radiation wavelength seen by the human eye
Light
Light that passes through a surface, all other is reflected or absorbed
Transmitted
Material that allows for an image to pass through (glass)
Transparent
Material that changes an image while allowing it to pass through (lens)
Refraction
Material that allows light to pass through, but not an image (frosted glass)
Translucent
Material that bounces a light off
Reflective
Material that reflects or absorbs all light
Opaque
The ratio of the total transmitted like to the total incident like represented as a percentage
Coefficient of transmission
The ratio of total reflected light to total incident light expressed as a percentage
Reflectance coefficient
Light bouncing off a material
Reflection
Results from a smooth polished surface like a mirror. The angle of incidence equals the angle of reflection.
Specular reflection
Results from a uniformly rough surface. It appears uniformly birth and the image of the source cannot be seen.
Diffuse reflection
Makes surface appear to be brighter at the point where the source is shining than in surrounding areas
Combined specular
The measure of light in terms of perceived brightness to the human eye
Photometry
The amount of light put out by a source
Intensity (I)
The measurement for the intensity of a source, and approximately equal to the horizontal output from a single candle
Candlepower (CP)
SI unit of luminous flux, a measurement of the total amount of visible light admitted by a source.
One unit of luminous flux uniformly cast on one square foot of area creates an illuminate of one footcandle.
Lumen (L)
The flow of light from a source into space
Flux (F)
The amount of light arriving at a surface
Illumination (E)
The calculated amount of illumination on a surface
Footcandle (FC)
The measurement of how bright light leaving an illuminated surface is… It depends on reflectivity or transmittance
Luminance
The density of limitless energy expressed as lumens per unit area
Illuminance
Unit of luminance or brightness
Lambert
Ratio between lumens reaching the working plane in a specific space and the lumens. Typically provided by the luminaire manufacturer, it’s an indication of the effectiveness of the luminaire in delivering light in a given space.
Coefficient of utilization (CU)
Ratio of fixture lumen output per wall of lamp input
Luminaire efficacy rating (LER)
Effect of temperature and voltage variations, dirt accumulation on luminaires and room services, lamp output depreciation, maintenance conditions.
Light loss factor (LLF)
The amount of light produced versus the power input (lumens/watt)
Efficacy
Difference and illumination level between one point and nearby points.
Contrast
Theoretical sphere surrounding an object being illuminated with light, cast evenly and illuminating any shadows and reflected bright spots
Equivalent spiracle illumination (ESI)
Measure of the effectiveness of the stores to make colors “right” to the viewer. The best possible rating is 100. 85+ is good
Color rendering index (CRI)
A characteristic of visible light where it’s color reveals its temperature.
Color temperature (K)
Intensity (I) / distance (d) ^2
Illumination (E)
Controls the amount of brightness admitted
Iris
Sensing device
Retina
Sense color
Cones
Since black-and-white
Rods
Visible light has a wavelength of about:
380–740 nm
The dormant wavelength determines
The perceived color
At the lower end of the visible light spectrum
Infrared
At the higher range of the visible light spectrum
Ultraviolet
Color temperature is when a light absorbing body is heated, it first glows …
First close to Fred, and orange, until it becomes blue/white hot.
Clear glass has a coefficient of transmission level of
85%
Frosted glass has a coefficient of transmission level of
70-85%
Contrast and brightness ratio:
Task to adjacent surroundings
1:1/3
Contrast and brightness ratio:
Task to more remote darker surfaces
1:1/5
Contrast and brightness ratios:
Task to more remote lighter surfaces
1:10
Sunlight footcandles:
10,000 footcandles
Full daylight footcandles
1000 footcandles
Overcast day footcandles
100 foot candles
Very dark day footcandles
10 footcandles
Twilight footcandles
One footcandle
Full moon footcandle
.01 footcandles
Minimum footcandles for emergency egress
One footcandle
General office work footcandles
50 foot candles
Footcandles for intricate tasks
150 foot candles
Candles for medium contrast tasks
Drafting
75 footcandles
If you surface will exhibit uniform brightness the spacing between light sources does not exceed approximately__their distance from the material.
1.5 times their distance from the material
Photometric readings are usually taken at the height of:
The working plane because this approximate height to typical visual tasks
Permanent supplementary artificial lighting of interiors (PSALI)
Begins with natural light, does that amount varies during the day, illumination levels vary within a room. Blending daylight and artificial light retains most of the physiological advantages, so lamps should match natural light color.
A method of calculating illumination for services not perpendicular to the source. Good for a single fixture or small number of fixtures. Takes into account orientation in distance but ignore surrounding reflection.
Point grid method
Used to calculate uniform illuminance in the space, based on the uniform distribution of a large number of fixtures. Takes into account reflectivity this space.
Zonal cavity method
Factors included in the zonal cavity method:
Light loss factors: Lamp lumen depreciation Ballast factor Luminaire dirt depreciation Room surface dirt depreciation
