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INTERNATIONAL ISO
STANDARD 80000-7
Second edition
2019-08
Quantities and units —
Part 7:
Light and radiation
Grandeurs et unités —
Partie 7: Lumière et rayonnements
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction — Special remarks .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
Bibliography .31
Alphabetical index .32
Foreword
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This document was prepared by Technical Committee ISO/TC 12, Quantities and units, in collaboration
with Technical Committee IEC/TC 25, Quantities and units.
This second edition cancels and replaces the first edition (ISO 80000-7:2008), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— the table giving the quantities and units has been simplified;
— some definitions and the remarks have been stated physically more precisely.
A list of all parts in the ISO 80000 and IEC 80000 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www. iso. org/members. html.
iv © ISO 2019 – All rights reserved
Introduction — Special remarks
0.1 Quantities
ISO 80000-7 contains a selection of quantities pertaining to light and other electromagnetic
radiation. Radiometric quantities relating to radiation in general may be useful for the whole range of
electromagnetic radiations, whereas photometric quantities pertain only to visible radiation.
In several cases, the same symbol is used for a trio of corresponding radiant, luminous and photon
quantities with the understanding that subscripts “e” for energetics, “v” for visible and “p” for photon
will be added whenever confusion among these quantities might otherwise occur.
For ionizing radiation, however, see ISO 80000-10.
Several of the quantities in ISO 80000-7 can be defined for monochromatic radiation, i.e. radiation of
a single frequency v only. They are denoted by their reference quantity as an argument like q(v). An
example is speed of light in a medium c(v), or the refractive index in a medium n(v) = c /c(v) Some of
those quantities are derivatives
dqq()λ ()λλ+D −q()λ
q′ λ = = lim
()
dλ Dλ→0 Dλ
of a quantity which are also frequently described as fractions Δq(λ) of a quantity q corresponding to the
radiation with wavelength in the interval λλ, +Dλ divided by the range Δλ of that interval to point to
[]
the physical measurement process behind. Such fractions must be additive so that the integral yields
the overall quantity, e.g. radiance (item 7-6.1) and spectral radiance (item 7-6.2). These derivatives of
quantities are called spectral quantities and are denoted by subscript λ.
On the other hand, some multidimensional quantities like radiant intensity I ()ϑϕ, , irradiance
e
Ex(),y , radiance Lx(),,y ϑϕ, , etc., are quantities that are strictly defined as values of a derivative at
e e
a certain point, a certain direction or at a certain point and direction in space. Hence, the most
fundamental definition according to ISO 80000-2 would be e.g. in case of the most complex term
“radiance” (item 7-6.1):
“at a given point xy, of a real or imaginary surface, in a given direction ϑϕ, ,
() ()
11 11
xx=
¶ ΦΦ()xy,,ϑϕ, ¶
ee
Lx(),,y ϑϕ, = =
e
yy=
¶¶Ax(),cyA⋅⋅osεϑW(),cϕε¶ ⋅⋅os ¶¶W 1
ϑϑ=
ϕϕ=
where Φ ()xy,,ϑϕ, represents the radiant flux transmitted through an area A(x, y) at a given
e
point (x , y ) and propagating in a given direction ϑϕ, , and ε is the angle between the normal
()
1 1
Ax ,y to that area at the given point and the given direction ϑϕ, ”.
() ()
11 11
To ease the use of the table in Clause 3, the simplified definitions (like item 7-6.1 in case of radiance) are
used which assume that fractions of quantities are always isotropic and uniform and continuous. In this
case, the given definitions are equivalent to the fundamental approach given above.
Instead of frequency v, other reference quantities of light may be used: angular frequency ων=2p ,
wavelength in a medium λν=cn/( ) , wavelength in vacuum λν=c / , wavenumber in medium σ = 1/λ,
0 00
wavenumber in vacuum νν==//cnσλ=1/ , etc. As an example, the refractive index may be given as
n(λ = 555 nm) ≈ 1,333.
Spectral quantities corresponding to different reference quantities are related, e.g.
dq==qv()dv qd()ωω==qv()dv qd()λλ=qd()σσ
vvωλ σ
thus
qqνω=⋅2p =qcνλ //=qc⋅=nq σ ⋅nc/
() () () () ()
νω νλ 00 σ 0
From the theoretical point of view, the frequency v is the more fundamental reference quantity, keeping
its value when a light beam passes through media with different refractive index, n. For historical
reasons, the wavelength, λ, is still mostly used as a reference quantity as it had been the most accurately
measured quantity in the past. In this respect, spectral quantities, as the spectral radiance (item 7-6.2),
L λ , have the meaning of spectral “densities” corresponding to the respective integrated quantities
()
e,λ
– i.e. in the case of radiance, L λ (item 7-6.1),
()
e
¶L
e
L =
e,λ
¶λ
0.2 Units
In photometry and radiometry, the unit steradian is retained for convenience.
0.3 Photopic quantities
In the great majority of instances, photopic vision (provided by the cones in the human visual system
and used for vision in daylight) is dealt with. Standard values of the spectral luminous efficiency function
V(λ) for photopic vision were originally adopted by the International Commission on Illumination (CIE)
in 1924. These values were adopted by the International Committee for Weights and Measures (CIPM)
(see BIPM Monograph in Reference [11]).
0.4 Scotopic quantities
For scotopic vision (provided by the rods and used for vision at night), corresponding quantities are
defined in the same manner as the photopic ones (items 7-10 to 7-18), using symbols with a prime.
For the term “spectral luminous efficiency” (item 7-10.2), the remarks would read:
“Standard values of luminous efficiency function V ' λ for scotopic vision were originally adopted
()
[11]
by CIE in 1951. They were later adopted by the CIPM .”
For the term “maximum luminous efficacy” (item 7-11.3), the definition would read:
“ maximum value of the spectral luminous efficacy for scotopic vision”
In the Remark it would read:
vi © ISO 2019 – All rights reserved
“The value is calculated by
−1
683lmW
' −1
K = ≈1700lmW
m
V' λ
()
cd
where V '()λ is the spectral luminous efficiency in terms of wavelength λ for scotopic vision and
λ is the wavelength in air corresponding to the frequency 540·10 Hz given in the definition of
cd
the SI unit candela.”
0.5 Mesopic quantities
For mesopic vision (provided by the rods and cones and used for vision intermediate between photopic
and scotopic vision), corresponding quantities are defined in the same manner as the photopic ones
(items 7-10 to 7-18), using symbols with the subscript “mes”.
For the term “spectral luminous efficiency” (item 7-10.2), the remarks would read:
“Standard values of spectral luminous efficiency functions V λ for mesopic vision depend on
()
mes
[12]
the used adaptation level m and were originally recommended by CIE in 2010 . They are adopted
[11]
by the CIPM .”
For the term “maximum luminous efficacy” (item 7-11.3), the definition would read:
“ adaptation level m dependent maximum value of the spectral luminous effi-
cacy for mesopic vision”
In the Remark it would read:
“The value is calculated by
−1
683lmW
K =
mm,;esm
V λ
()
mesc;m d
where V ()λ is the spectral luminous efficiency for mesopic vision at an adaptation level m
mes;m
and λ is the wavelength in air corresponding to the frequency 540·10 Hz given in the defini-
cd
tion of the SI unit candela.”
INTERNATIONAL STANDARD ISO 80000-7:2019(E)
Quantities and units —
Part 7:
Light and radiation
1 Scope
This document gives names, symbols, definitions and units for quantities used for light and optical
radiation in the wavelength range of approximately 1 nm to 1 mm. Where appropriate, conversion
factors are also given.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
Names, symbols, definitions and units for quantities used in light and optical radiation in the wavelength
range of approximately 1 nm to 1 mm are given in Table 1.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
In the field of light, the CIE maintains the Electronic international lighting vocabulary, available at http:
//eilv .cie .co .at/.
2 © ISO 2019 – All rights reserved
Table 1 — Quantities and units used in light and optical radiation in the wavelength range of approximately 1 nm to 1 mm
Item No. Quantity Unit Remarks
Name Symbol Definition
−1
7-1.1 speed of light in a c phase speed of an electromagnetic wave m s See also ISO 80000-3.
medium at a given point in a medium
The value of the speed of light in a medium can depend
on the frequency, polarization, and direction.
For the definition of the speed of electromagnetic
waves in vacuum, c , see ISO 80000-1.
7-1.2 refractive index n quotient of speed of light in vacuum 1 The value of the refractive index can depend on the
(ISO 80000-1) and speed of light in a frequency, polarization, and direction.
medium (item 7-1.1)
The refractive index is expressed by n = c /c, where
c is the speed of light in vacuum and c is the speed of
light in the medium.
For a medium with absorption, the complex refractive
index n is defined by
n = n + ik
where k is spectral absorption index (IEC 60050-845)
and i is imaginary unit.
The refractivity is expressed by n −1, where n is refrac-
tive index.
7-2.1 radiant energy Q , W, U energy (ISO 80000-5) emitted, trans- J Radiant energy can be expressed by the time integral
e
ferred or received in form of electromag- of radiant flux (item 7-4.1), Φ , over a given duration
2 −2 e
(Q) kg m s
netic waves (ISO 80000-3), Δt
Qt= Φ d
ee∫
Dt
Radiant energy is expressed
...