|
Quantity |
Symbol |
Unit |
Formula
/
Reference |
Definition |
|
Luminous
intensity |
I |
candela
(cd) |
I
=
Φ/ω |
Quotient
of luminous flux in the element of a solid angle in a given
direction, by the element of the solid
angle. |
|
Illuminance |
E |
lux
(lx) |
E
=
Φ/A |
Quotient
of luminous flux incident on an element of a surface, by the
area of that element. |
|
Luminance
(light
density) |
L |
|
L =
I/A
(L=I/Acosα) |
Quotient
of luminous intensity of a light emitted or reflected in a
given direction from a surface element, by projected area of
that element. |
|
Luminous
flux |
Φ |
lumen
(lm) |
Φ
=
Iω |
Quantity
derived from the radiant flux by evaluating the radiation
according to its action upon the CIE standard photometric
observer,
(Vx-curved) |
|
Design
lumen
(Design
lumen) |
Φta
250C |
lumen |
|
Luminous
flux from a light source (e.g.T5) at ambient temperature of
25ºC measured under reference
conditions.
The
luminous flux can differ from the maximum flux of the light
source. |
|
Light
output ratio working
(of
a luminaire) |
ηw |
|
|
Ratio
of the luminous flux of the luminaire, measure under specified
practical conditions with its own lamps and equipment to the
sum of the individual luminous fluxes of the same lamps when
operating outside the luminaire with reference ballast, under
specified conditions. |
|
Ballast
Lumen Factor |
BLF |
- |
- |
Is
the ratio of the light output of the same lamps measured with
a commercial ballast and measured under reference conditions
both at an ambient temperature of
25ºC. |
|
Colour
temperature |
K |
kelvin |
CIE
17.4 |
The
temperature of a Planckian radiator whose radiation has the
same chromatically as that of a given
stimulus. |
|
Colour
rendering |
Ra |
Ra-index |
CIE
17.4 |
The
effect of an illuminant on the colour appearance of an object
by conscious or subconscious comparison with their colour
appearance under a reference
illuminant. |
|
Luminous
efficacy
-
of a light source |
|
(lm/W) |
η=Φ/P |
Quotient
of the luminous flux emitted by the power consumed by the
light source. |
|
Luminous
efficacy
–
light source + ballast |
|
(lm/W) |
η=Φ/P |
Quotient
of he luminous flux emitted by the power consumed by the light
source including ballast losses. |
|
Glare |
|
|
CIE
- 31,
112,
117 |
Condition
of which there is to see discomfort or reduction in ability to
see detail objects, caused by an unsuitable distribution or
range of luminance or to an extreme
contrasts.
Glare
is normally subdivided into disability or discomfort glare,
-
disability glare (TI/GR) – impairs the vision of objects with
necessarily causing discomfort.
-
discomfort glare (UGR/NB) – causes discomfort without
necessarily impairing the vision of
objects. |
|
Uniformity
-
Illuminance uniformity
-
Luminance uniformity |
|
|
