EN ISO/CIE 11664-2:2022

SLOVENSKI STANDARD
01-december-2022
Nadomešča:
SIST EN ISO 11664-2:2011
Kolorimetrija - 2. del: Standardizirana osvetljevala (iluminanti) CIE (ISO/CIE 11664-
2:2022)
Colorimetry - Part 2: CIE standard illuminants (ISO/CIE 11664-2:2022)
Farbmetrik - Teil 2: CIE Normlichtarten (ISO/CIE 11664-2:2022)
Colorimétrie - Partie 2: Illuminants CIE normalisés (ISO/CIE 11664-2:2022)
Ta slovenski standard je istoveten z: EN ISO/CIE 11664-2:2022
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO/CIE 11664-2
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2022
EUROPÄISCHE NORM
ICS 17.180.20 Supersedes EN ISO 11664-2:2011
English Version
Colorimetry - Part 2: CIE standard illuminants (ISO/CIE
11664-2:2022)
Colorimétrie - Partie 2: Illuminants CIE normalisés Farbmetrik - Teil 2: CIE Normlichtarten (ISO/CIE
(ISO/CIE 11664-2:2022) 11664-2:2022)
This European Standard was approved by CEN on 2 August 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/CIE 11664-2:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO/CIE 11664-2:2022) has been prepared by Technical Committee CIE
"International Commission on Illumination" in collaboration with Technical Committee CEN/TC 139
“Paints and varnishes” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2023, and conflicting national standards shall
be withdrawn at the latest by March 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 11664-2:2011.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO/CIE 11664-2:2022 has been approved by CEN as EN ISO/CIE 11664-2:2022 without any
modification.
INTERNATIONAL ISO/CIE
STANDARD 11664-2
First edition
2022-08
Colorimetry —
Part 2:
CIE standard illuminants
Colorimétrie —
Partie 2: Illuminants CIE normalisés
Reference number
ISO/CIE 11664-2:2022(E)
© ISO/CIE 2022
ISO/CIE 11664-2:2022(E)
© ISO/CIE 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester
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Fax: +41 22 749 09 47
Email: copyright@iso.org Email: ciecb@cie.co.at
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Published in Switzerland
ii
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 S c op e . 1
2 Nor m at i ve r ef er enc e s . 1
3 Terms and definitions . 1
4 CIE standard illuminant A . 2
4.1 Definition . 2
4 . 2 T he or e t ic a l b a s i s . 2
5 CIE standard illuminant D65 .3
5.1 D efinition . 3
5.2 E xperimental basis . 3
5.3 C orrelated colour temperature . 3
6 CIE standard illuminant D50 . 3
6.1 Definition . 3
6.2 C orrelated colour temperature . 3
7 S ources for realizing CIE standard illuminants . 4
7.1 S ource for CIE standard illuminant A . 4
7.2 S ources for CIE standard illuminants D65 and D50 . 4
Annex A (informative) Table of relative spectral power distribution of CIE standard
illuminant A . 5
Annex B (normative) Table of relative spectral power distributions of CIE standard
illuminants D65 and D50 .18
Annex C (informative) History of the definition of CIE standard illuminant A .31
Bibliography .32
iii
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by the International Commission on Illumination (CIE) in cooperation
with Technical Committee ISO/TC 274, Light and lighting, in collaboration with the European Committee
for Standardization (CEN) Technical Committee CEN/TC 139, Paints and varnishes, in accordance with
the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This first edition cancels and replaces ISO 11664-2:2007/CIE S 014-2:2006, which has been technically
revised.
The main changes are as follows:
— CIE illuminant D50 has been included as CIE standard illuminant because of its extensive use in the
fields of graphic, arts and photography.
A list of all parts in the ISO/CIE 11664 series can be found on the CIE and ISO websites.
Any feedback or questions on this document should be directed to the CIE Central Bureau or the user’s
national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.
iv
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
Introduction
The illuminants defined in this document are as follows:
a) CIE standard illuminant A
CIE standard illuminant A is intended to represent typical tungsten-filament lighting. Its relative
spectral power distribution is that of a Planckian radiator at a temperature of approximately 2 855,5 K.
CIE standard illuminant A should be used in all applications of colorimetry involving the use of
incandescent lighting, unless there are specific reasons for using a different illuminant. CIE standard
illuminant A is used in photometry as primary reference spectrum for the calibration of photometric
devices.
b) CIE standard illuminant D65
CIE standard illuminant D65 is intended to represent average daylight having a correlated colour
temperature of approximately 6 500 K. CIE standard illuminant D65 should be used in all colorimetric
calculations requiring representative outdoor daylight, unless there are specific reasons for using a
different spectral power distribution. Variations in the relative spectral power distribution of daylight
are known to occur, particularly in the ultraviolet spectral region, as a function of season, time of day
and geographic location. However, CIE standard illuminant D65 is used pending the availability of
additional information on these variations.
c) CIE standard illuminant D50
CIE standard illuminant D50 is intended to represent daylight with a correlated colour temperature of
approximately 5 000 K. CIE standard illuminant D50 should be used in colorimetric calculations where
the use of such a correlated colour temperature is intended.
Values for the relative spectral power distribution of CIE standard illuminants A, D65 and D50 are given
in this document at 1-nm intervals from 300 nm to 830 nm.
The term “illuminant” refers to a defined spectral power distribution, not necessarily realizable or
provided by an artificial source. Illuminants are used in colorimetry to compute the tristimulus values
of reflected or transmitted object colours under specified conditions of illumination. The CIE has also
defined other illuminants, such as illuminant C, other daylight illuminants, and illuminants for LED and
other electric light sources. These illuminants are described in CIE 015, but they do not have the status
of CIE standard illuminants. It is recommended that one of the three CIE standard illuminants defined
in this document be used wherever possible. This will greatly facilitate the comparison of published
results.
In most practical applications of colorimetry, it is sufficient to use the values of CIE standard illuminants
A, D65 and D50 at less frequent wavelength intervals or in a narrower spectral region than specified in
this document. Data and guidelines that facilitate such practice are provided in CIE 015, together with
other recommended procedures for practical colorimetry.
The term “source” refers to a physical emitter of light, such as a lamp or the sun. In certain cases, the CIE
recommends laboratory sources that approximate the spectral power distributions of CIE illuminants.
In all cases, however, the definition of a CIE-recommended source is secondary to the definition of the
corresponding CIE illuminant, because of the possibility that, from time to time, new developments will
lead to improved sources that represent a particular illuminant more accurately or are more suitable
for laboratory use.
CIE standard source A, the practical realization of CIE standard illuminant A, is described in this
document. At present, there are no CIE-recommended sources representing CIE standard illuminants
D65 and D50.
v
© ISO/CIE 2022 – All rights reserved

INTERNATIONAL STANDARD ISO/CIE 11664-2:2022(E)
Colorimetry —
Part 2:
CIE standard illuminants
1 S cope
This document defines three CIE standard illuminants for use in colorimetry: CIE standard illuminant
A for the representation of typical tungsten-filament lighting, CIE standard illuminant D65 for the
representation of average daylight having a correlated colour temperature of approximately 6 500 K and
CIE standard illuminant D50 for the representation of daylight with a correlated colour temperature of
approximately 5 000 K. Values of the relative spectral power distribution of the three illuminants are
included in this document.
2 Normat ive references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
CIE S 017, ILV: International Lighting Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CIE S 017 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
CIE maintains a terminology database for use in standardization at the following address:
— CIE e-ILV: available at http:// cie .co .at/ e -ilv
3.1
illuminant
radiation with a relative spectral power distribution defined over the wavelength range that influences
object colour perception
[SOURCE: CIE S 017:2020, Entry 17-23-018, modified — Notes to entry omitted.]
3.2
CIE standard illuminant
illuminant standardized by the CIE for the purpose of harmonization
[SOURCE: CIE S 017:2020, Entry 17-23-021, modified — Notes to entry omitted.]
3.3
CIE standard source
artificial source specified by the CIE whose radiation approximates a CIE standard illuminant
[SOURCE: CIE S 017:2020, Entry 17-23-022, modified — Notes to entry omitted.]
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
3.4
daylight illuminant
D illuminant
illuminant having the same or nearly the same relative spectral power distribution of the radiant flux
as a phase of daylight
[SOURCE: CIE S 017:2020, Entry 17-23-020, modified — Notes to entry omitted.]
3.5
standard air
dry air at 15 °C and 101 325 Pa, containing 0,045 % by volume of carbon dioxide
[SOURCE: CIE 018:2019, Clause 3]
4 CIE standard illuminant A
4.1 Definition
The relative spectral power distribution of CIE standard illuminant A, S (λ), is defined by Formula (1)
A
over the wavelength range 300 nm to 830 nm.
1,435×10
5 exp −1
 
2 848×560
S ()λ = 100 × (1)
A
 
λ
  1,435×10
exp −1
2 8848 λ
where λ is the wavelength in nanometres and the numerical values in the two exponential terms are
definitive constants originating from the first definition of illuminant A in 1931 (see also Annex C).
This spectral power distribution is normalized to the value 100 (exactly) at the wavelength 560 nm
(exactly).
NOTE Table A.1 in Annex A provides the relative spectral power distribution of CIE standard illuminant A to
six significant digits, at 1-nm intervals. For practical purposes it suffices to use these tabulated values instead of
the values calculated from Formula (1).
Despite the fact that Formula (1) is based on Planck's equation for vacuum, the wavelengths are to be
taken as being in standard air (see 3.5). This makes CIE standard illuminant A compatible with other
CIE colorimetric and photometric data.
4.2 Theoretical basis
Formula (1) is equivalent to and can be derived from Formula (2):
MT(,λ )
e,λ
S ()λ =100 (2)
λ
MT(,560 )
e,λ
where
−1
 
c
 
−5 2
MT(,λλ)e=c xp −1 ;
   
e,λ 1
λT
   
 
λ is the wavelength (in nm);
the quotient c /T is given by 14 350 μm⋅K/2 848 K = (1,435 × 10 /2 848) nm.
Since the numerical value of c cancels out Formula (2), this definition of CIE standard illuminant A
involves no assumptions about the numerical values of c , c and T other than the quotient c /T.
1 2 2
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
The constant c is calculated from h · c/k and its value is 14 387,768 55 … μm·K, using the values of
the Planck constant, h, the speed of light in vacuum, c, and the Boltzmann constant, k, as specified in
[1]
The International System of Units . Using this value for c , the assigned temperature for CIE standard
illuminant A is 2 855,496 . K, thus approximately 2 855,5 K.
NOTE More information regarding the historical changes to the temperature used to define CIE standard
illuminant A can be found in Annex C.
5 CIE standard illuminant D65
5.1 Definition
CIE standard illuminant D65 shall be as defined in Annex B by the relative spectral power distribution
values provided in Column 2 of Table B.1. The values are presented at 1-nm intervals over the wavelength
range from 300 nm to 830 nm; the wavelength values given apply in standard air. If required, other
intermediate values shall be derived by linear interpolation from the published values.
5.2 Experimental basi s
The relative spectral power distribution of CIE standard illuminant D65 is based on experimental
measurements of daylight in the wavelength range 330 nm to 700 nm, with extrapolations to 300 nm
[2]
and 830 nm, as reported by Judd et al. The extrapolated values are believed to be sufficiently accurate
for conventional colorimetric purposes, but are not recommended for non-colorimetric use.
5.3 C orrelated colour temperature
CIE standard illuminant D65 has a nominal correlated colour temperature of 6 500 K.
[3]
NOTE Using the value of c = 14 388 μm·K specified in the International Temperature Scale of 1990, the
definition of correlated colour temperature (CIE S 017, 17–23–068) and the relative spectral power distribution
data of Table B.1, the correlated colour temperature of CIE standard illuminant D65 is found to be 6 502,712 K.
Using the value of c = 14 387,768 775 … μm·K, as shown in 4.2, the definition of correlated colour temperature
(CIE S 017, 17–23–068) and the relative spectral power distribution data of Table B.1, the correlated colour
temperature of CIE standard illuminant D65 is found to be 6 502,608 K. The difference from the nominal
correlated colour temperature of 6 500 K of CIE standard illuminant D65 is judged to be insignificantly small.
6 CIE standard illuminant D50
6.1 Definition
CIE standard illuminant D50 shall be as defined in Annex B by the relative spectral power distribution
values provided in Column 3 of Table B.1. The values are presented at 1-nm intervals over the wavelength
range from 300 nm to 830 nm; the wavelength values given apply in standard air. If required, other
intermediate values shall be derived by linear interpolation from the published values.
6.2 C orrelated colour temperature
CIE standard illuminant D50 has a nominal correlated colour temperature of 5 000 K.
[3]
NOTE Using the value of c = 14 388 μm·K specified in the International Temperature Scale of 1990, the
definition of correlated colour temperature (CIE S 017, 17–23–068) and the relative spectral power distribution
data of Table B.1, the correlated colour temperature of CIE standard illuminant D50 is found to be 5 001,319 K.
Using the value of c = 14 387,768 775 … μm·K, as shown in 4.2, the definition of correlated colour temperature
(CIE S 017, 17–23–068) and the relative spectral power distribution data of Table B.1, the correlated colour
temperature of CIE standard illuminant D50 is found to be 5 001,239 K. The difference from the nominal
correlated colour temperature of 5 000 K of CIE standard illuminant D50 is judged to be insignificantly small.
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
The actual correlated colour temperature of CIE standard illuminant D50 is slightly different from
5 000 K; however, this is judged to be visually insignificant.
7 S ources for realizing CIE standard illuminants
7.1 S ource for CIE standard illuminant A
CIE standard illuminant A can be realized by CIE standard source A, defined as a gas-filled, tungsten-
filament lamp operating at an assigned temperature T = (2 848 K/14 350 μm⋅K) ⋅ c where c is
2, 2
expressed in μm·K. A lamp with a fused-quartz envelope or window is recommended if the spectral
power distribution of the ultraviolet radiation of CIE standard illuminant A is to be realized more
accurately.
The assigned temperature, T, is currently approximated to 2 855,5 K as shown in 4.2.
7.2 S ources for CIE standard illuminants D65 and D50
At present, there are no CIE-recommended standard sources for realizing CIE standard illuminants D65
and D50. The quality of sources intended for laboratory realization of CIE standard illuminant D65 or
[4]
D50 can be assessed by a method described in ISO 23603/CIE S 012.
© ISO/CIE 2022 – All rights reserved

ISO/CIE 11664-2:2022(E)
Annex A
(informative)
Table of relative spectral power distribution of CIE standard
illuminant A
CIE standard illuminant A is defined by Formula (1) in 4.1. Table A.1 is provided for practical use only.
Table A.1 — Relative spectral power distribution of CIE standard illuminant A (wavelengths in
standard air)
λ/nm S (λ)
A
300 0,930 483
301 0,967 643
302 1,005 97
303 1,045 49
304 1,086 23
305 1,128 21
306 1,171 47
307 1,216 02
308 1,261 88
309 1,309 10
310 1,357 69
311 1,407 68
312 1,459 10
313 1,511 98
314 1,566 33
315 1,622 19
316 1,679 59
317 1,738 55
318 1,799 10
319 1,861 27
320 1,925 08
321 1,990 57
322 2,057 76
323 2,126 67
324 2,197 34
325 2,269 80
326 2,344 06
327 2,420 17
328 2,498 14
329 2,578 01
330 2,659 81
331 2,743 55
332 2,829 28
© ISO/CIE 2022 – All rights reserved

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