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Technical
Glossary of terms
Ballast lumen factor BLF (%)
Refers to the ratio of light output from the lamp on emergency operation to the
nominal light output.
Beam Angle
Indicates how broadly the light is emitted from a reflector lamp. It can be thought of as
an imaginary cone whose apex intersects the lamp face, and the breadth of the cone
extends outwards to the point where luminous intensity has diminished to 50% of the
centre beam value.
Binning
The term binning refers to the variations which occur within a single production batch
of LED’s such as chromaticity, lumen output and forward voltage. It is important that a
specific bin has been identified and selected to ensure a uniform and constantly even
lighting installation is achieved. If all the LED’s were selected from one production
batch and used in the same luminaire or installation, there would be a mix of colour
temperatures and brightness levels. For the lighting manufacturer / designer binning is an
essential part of LED specification.
MacAdam ellipses methodology was created in 1943 for mathematically constructing
ellipses around target points, something which became very useful for the lamp industry.
ANSI C78.377 is now the standard for chromaticity specified by the American National
Standards Institute. ANSI recommends that lamp manufacturers stay within a “4-step”
ellipse. This means that, given a certain target point on the CIE diagram, manufacturers
are given a fairly wide range of perceptible differences.
Candela (cd)
The unit of measurement for luminous intensity, which refers to the quantity of light
emitted in a particular direction. The symbol is cd.
Colour Correlated Temperature (CCT)
An incandescent light bulb is very close to a perfect black-body radiator, so its colour
temperature is basically the temperature of the filament. However many light sources,
such as fluorescent tubes or high intensity discharge lamps, emit light by processes
other than thermal radiation and therefore it is not possible to apply the black-body
spectrum. For these light sources it is possible to assign what is known as a colour
correlated temperature (CCT). The CCT is the colour temperature of a black-body
(Planckian) radiator which most closely matches the colour of the light emitted
from the lamp.
Colour Rendering Index (CRI)
The colour rendering of a light source is an indicator of its ability to realistically
reproduce the colour of an object. The chart illustrates our ability to accurately
determine colour depending on the colour rendering properties of the light source.
The higher the colour rendering index (on a scale of 0 to 100) of the source the better
our ability to perceive differences in colour, which is a considerable aid to highlighting
fashion products and effective display of coloured artworks.
The CIE colour rendering index (CRI) is a method to determine how well a light source’s
illumination of eight standardised colour patches compares to the illumination provided
by a reference source. At Ra (8) the perceived colour shift of eight reference colours is
measured as a percentage and averaged to give one number. However it is currently
understood that due to the spectral power distribution of LED’s that instead of using the
standard Ra8 it is important to include 7 additional colours which include red, yellow,
blue & green and use Ra14 to ensure better results.
Colour Temperature
Colour temperature is a characteristic of visible light that plays a significant role in
lighting applications. The colour temperature of a light source is the temperature of
a perfect black-body radiator that radiates light of a similar appearance to that of the
light source. The colour temperature is measured in units of absolute temperature;
Kelvin (K).
Colour temperature works paradoxically to our cultural associations with colour, red as
hot and blue as cold. On the black-body curve, blue occurs at higher temperatures than
red. A good example is a candle which has a warm red orange appearance but in fact
has a low Kelvin temperature, 1850K. Therefore higher colour temperatures
(5000K more) are called cool colours (blueish white); lower colour temperatures (2700 –
3000K) are called warm colours (yellowish white through red).
0.9
520
700
380
10000
6000
Tc(ºK)
4000
3000 2500
2000 1500
460
470
480
490
0.8
0.7
0.6
0.5
Y
X
Y
Y
0.4
0.3
0.2
0.1
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.30
0.30
0.35
0.40
0.45
6
Ch
M
ex
0.43
0.41
0.42
0.40
Typical application
The Planckian locus shows the chromaticities of black-body light
sources of various colour temperatures and lines of constant
correlated colour temperature shown within the CIE chromaticity
diagram
Warm White 3000K
Neutral White 4000K
0.9
520
700
380
10000
6000
Tc(ºK)
4000
3000 2500
2000 1500
460
470
480
490
0.8
0.7
0.6
0.5
Y
X
Y
Y
0.4
0.3
0.2
0.1
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
0.30
0.35
ANSI C78.3
0.30
0.35
0.40
0.45
400
4500K
5000K
5700K
6500K
+ Special Colours = Ra14
General Colours Ra8
ci l
l rs
Chromaticity range char
MacAdam ellipses 3
Hour
Relative Light Output at Tj
/
ex. 3000K
0.43
0.41
0.42
0.40
0.39
0.38
100%
90%
80%
70%
60%
50%
0
10K 20K
3.2
XX
XX
17.5
1.6
30K
0.41
0.42
0.43
3220K
Chromaticity range
14 Ø
11 Ø
Anode
1A (Ra>90)
1B (90>Ra>80)
2A (80>Ra>70)
2B (70>Ra>60)
3 (60>Ra>40)
4 (40>Ra>20)
Typical application
Accurate
Medical examination, colour
printing inspection, art galleries
Good
Retail, showrooms, restaurants
o ces etc
Moderate
O ces, classrooms, security lighting
supermarkets, manual areas etc
Poor
Street lighting, parking areas etc
Not important
Street lighting
100
90
80
60
40
20
X
X
Y
Y
0.30
0.35
0.40
ANSI C78.377
3-steps Mac-Adam ellipses
0.45
0.50
0.30
0.35
0.40
0.45
2700K
BB Locus
3000K
3500K
4000K
4500K
5000K
5700K
6500K
Chromaticity range chart
MacAdam ellipses 3
Hours
Relative Light Output at Tj
/ 5 / 7 SDCM
ex. 3000K
L80
L70
0.43
0.41
0.42
0.40
0.39
0.38
100%
90%
80%
70%
60%
50%
0
10K 20K
3.2
3.25
18.5
22
XX
11
17.5
1.6
30K 40K 50K 60K 70K
0.41
0.42
0.43
0.44
0.45
0.46
Black Body Locus
2870K
3220K
3045K +/
-
135K
（
5SDCM
）
3045K +/
-
175K
（
7SDCM
）
Chromaticity range of ANSI C78.377 (3000K)
3045K +/
-
70 K
（
3SDCM
）
14 Ø
11 Ø
Anode
Cathode
700
380
000
6000
Tc(ºK)
4000
3000 2500
2000 1500
X
X
X
Y
Y
.2 0.3 0.4 0.5 0.6 0.7
0.30
0.35
0.40
ANSI C78.377
3-steps Mac-Adam ellipses
0.45
0.50
0.30
0.35
0.40
0.45
2700K
BB Locus
3000K
3500K
4000K
4500K
5000K
5700K
6500K
urs = Ra14
rs Ra8
rs
Chromaticity range chart
MacAdam ellipses 3
Hours
Relative Light Output at Tj
/ 5 / 7 SDCM
ex. 3000K
L80
L70
0.43
0.41
0.42
0.40
0.39
0.38
100%
90%
80%
70%
60%
50%
0
10K 20K
3.2
3.25
18.5
22
XX
XX
11
17.5
1.6
30K 40K 50K 60K 70K
0.41
0.42
0.43
0.44
0.45
0.46
Black Body Locus
2870K
3220K
3045K +/
-
135K
（
5SDCM
）
3045K +/
-
175K
（
7SDCM
）
Chromaticity range of ANSI C78.377 (3000K)
3045K +/
-
70 K
（
3SDCM
）
14 Ø
11 Ø
Anode
Cathode
1A (Ra>90)
1B (90>Ra>80)
2A (80>Ra>70)
2B (70>Ra>60)
3 (60>Ra> 0)
4 (40>Ra>20)
Typical application
Accurate
Medical examination, colour
printing inspection, art galleries
Good
Retail, showrooms, restaurants
o ces etc
Moderate
O ces, classrooms, security lighting
supermarkets, manual areas etc
Poor
Street lighting, parking areas etc
Not import nt
Street lighting