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4.1 Variable Definitions
English
Abbreviation
Duv
UV distance between CIE1960 plane coordinate(s) and Planck’s blackbody
radiation with the same color temperature. A value close to 0 indicates the
color temperature and color are closer to that of the blackbody radiation. A
positive value indicates it is above the blackbody radiation, while a negative
value indicates it is below the blackbody radiation.
Δx
X difference between CIE1931 plane coordinates and Planck’s blackbody
radiation with the same color temperature.
Δy
Y difference between CIE1931 plane coordinates and Planck’s blackbody
radiation with the same color temperature.
Δu'
U' difference between CIE1976 plane coordinates and Planck’s blackbody
radiation with the same color temperature.
Δv'
V’ difference between CIE1976 plane coordinates and Planck’s blackbody
radiation with the same color temperature.
fc
Non-SI unit of illuminance defined as lumens per square foot (lm/ft
2
).
Purity
Percent of the dominant wavelength in the standard illuminant. The closer
the color purity is to 100%, the closer it is to the dominant wavelength.
IRR
Flux of radiant energy per unit area within the range of a specified
wavelength.
PPFD
Number of photons per unit area per unit of time (Photon Flux Density, or
PFD) for photosynthetically-active radiation (400~700nm wavelength range).
PPFD-R
PFD in the 600~700 nm wavelength range.
PPFD-G
PFD in the 500~600 nm wavelength range.
Full Name
CIE1960 UV Color Coordinate Difference
CIE1931 Color Coordinate Difference
CIE1931 Color Coordinate Difference
CIE1976 Color Coordinate Difference
CIE1976 color coordinate difference
Foot-candle
Color Purity
Irradiance
Photosynthetic Photon Flux Density
PFD in Red Field
PFD in Green Field
Unit
fc
%
W/m
2
µmol m
-2
s
-1
µmol m
-2
s
-1
µmol m
-2
s
-1
- 17 -
4.1 Variable Definitions
Abbreviation
PPFD-B
PFD in the 400~500 nm wavelength range.
PFD-UV
PFD in the 380~400 nm wavelength range.
PFD-FR
PFD in the 700~780 nm wavelength range.
Full Name
PFD in Blue Field
PFD in UV Field
PFD in FR Field
Unit
µmol m
-2
s
-1
µmol m
-2
s
-1
µmol m
-2
s
-1
