®
Technical Support
PS
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3213
7
013-14935B
The following graphic of precise metrics for lighting has
images showing Luminous Flux, Luminous Intensity, Illu
-
minance, and Luminance.
Luminous Flux is the quantity of the energy of the light
emitted per second in all directions. In photometry, Lumi
-
nous Intensity is a measure of the wavelength-weighted
power emitted by a light source in a particular direction
per unit solid angle, based on the luminosity function, a
standardized model of the sensitivity of the human eye.
Illuminance is the amount of luminous flux per unit area.
The luminosity function (or luminous efficiency function)
describes the average spectral sensitivity of human
visual perception of brightness. It is based on subjective
judgments of which of a pair of different-colored lights is
brighter, to describe relative sensitivity to light of differ
-
ent wavelengths. In photometry, Illuminance is the total
luminous flux incident on a surface, per unit area. It is a
measure of how much the incident light illuminates the
surface, wavelength-weighted by the luminosity function
to correlate with human brightness perception. Lumi
-
nance is the intensity of light emitted from a surface per
unit area in a given direction.
UVA: Ultraviolet A is ultraviolet radiation with wave
-
lengths between 315 and 400 nm.
UVB: Ultraviolet B is ultraviolet radiation with wave
-
lengths between 290 and 320 nm, comprising less than
1 per cent of the ultraviolet radiation that reaches the
earth.
UV Index: The UV index is effectively a rough measure
of the amount of harmful ultraviolet radiation in the sun
-
light reaching the Earth's surface at a given location. The
index is a scale used to estimate the risk for sunburn in
midday sunlight, with a low number meaning less risk
than a high number.
PAR: (Photosynthetically Active Radiation) This desig
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nates the spectral range (wave band) of solar radiation
from 400 to 700 nm that photosynthetic organisms are
able to use in the process of photosynthesis. This spec
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tral region corresponds more or less with the range of
light visible to the human eye.
Illuminance: This is the total luminous flux incident on a
surface, per unit area. It is a measure of how much the
incident light illuminates the surface,
Irradiance: In radiometry, irradiance is the radiant flux
(power) received by a surface per unit area. The SI unit
of irradiance is the watt per square meter (W/m²).
Sample Data
The graph shows the measurement of light intensity ver
-
sus distance using the PS-3213 Wireless Light Sensor
Luminous
Intensity
(candelas)
Luminous
Flux
(lumens)
Illuminance
(lux = lumens/m²)
Luminance
(candelas/m²)
Precise Metrics for Lighting: Luminous Flux (lumens), Luminous Intensity (candelas), Illuminance (lux = lumens/m²). and Luminance (candelas/m²)
