prEN ISO/CIE 11664-2
(Main)Colorimetry - Part 2: CIE standard illuminants (ISO/CIE DIS 11664-2.2:2021)
Colorimetry - Part 2: CIE standard illuminants (ISO/CIE DIS 11664-2.2:2021)
Farbmetrik - Teil 2: CIE Normlichtarten (ISO/CIE DIS 11664-2.2:2021)
Dieses Dokument definiert drei CIE-Normlichtarten zur Anwendung in der Farbmetrik: CIE-Normlichtart A für die Repräsentation einer typischen Beleuchtung mit Wolfram-Glühfaden, CIE-Normlichtart D65 für die Repräsentation von durchschnittlichem Tageslicht mit einer korrelierten Farbtemperatur von etwa 6 500 K und CIE-Normlichtart D50 für die Repräsentation von Tageslicht mit einer korrelierten Farbtemperatur von etwa 5 000 K. Dieses Dokument enthält Werte für die Strahlungsfunktion der drei Lichtarten.
Colorimétrie - Partie 2: Illuminants CIE normalisés (ISO/CIE DIS 11664-2.2:2021)
Kolorimetrija - 2. del: Standardizirana osvetljevala (iluminanti) CIE (ISO/CIE DIS 11664-2.2:2021))
General Information
RELATIONS
Standards Content (sample)
SLOVENSKI STANDARD
oSIST prEN ISO/CIE 11664-2:2021
01-december-2021
Kolorimetrija - 2. del: Standardizirana osvetljevala (iluminanti) CIE (ISO/CIE DIS
11664-2.2:2021))Colorimetry - Part 2: CIE standard illuminants (ISO/CIE DIS 11664-2.2:2021)
Farbmetrik - Teil 2: CIE Normlichtarten (ISO/CIE DIS 11664-2.2:2021)
Colorimétrie - Partie 2: Illuminants CIE normalisés (ISO/CIE DIS 11664-2.2:2021)
Ta slovenski standard je istoveten z: prEN ISO/CIE 11664-2
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
oSIST prEN ISO/CIE 11664-2:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------oSIST prEN ISO/CIE 11664-2:2021
---------------------- Page: 2 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
DRAFT INTERNATIONAL STANDARD
ISO/CIE DIS 11664-2.2
CIE Secretariat: CIE
Voting begins on: Voting terminates on:
2021-10-22 2021-12-17
Colorimetry —
Part 2:
CIE standard illuminants
Colorimétrie —
Partie 2: Illuminants CIE normalisés
ICS: 17.180.20
Member bodies are requested to consult relevant national interests in ISO/TC
274 before casting their ballot to the e-Balloting application.
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/CIE DIS 11664-2.2:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO/CIE 2021
---------------------- Page: 3 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/CIE 2021
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.ISO copyright office CIE Central Bureau
CP 401 • Ch. de Blandonnet 8 Babenbergerstraße 9/9A
CH-1214 Vernier, Geneva A-1010 Vienna, Austria
Phone: +41 22 749 01 11 Phone: +43 1 714 3187
Email: copyright@iso.org Email: ciecb@cie.co.at
Website: www.iso.org Website: www.cie.co.at
Published in Switzerland
ii © ISO/CIE 2021 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
Contents
Foreword ................................................................................................................................................................iv
Introduction ........................................................................................................................................................... v
1 Scope .......................................................................................................................................................... 1
2 Normative references .......................................................................................................................... 1
3 Terms and definitions .......................................................................................................................... 1
4 CIE standard illuminant A ................................................................................................................... 2
4.1 Definition .................................................................................................................................................. 2
4.2 Theoretical basis .................................................................................................................................... 2
5 CIE standard illuminant D65 ............................................................................................................. 3
5.1 Definition .................................................................................................................................................. 3
5.2 Experimental basis ................................................................................................................................ 3
5.3 Correlated colour temperature ........................................................................................................ 3
6 CIE standard illuminant D50 ............................................................................................................. 4
6.1 Definition .................................................................................................................................................. 4
6.2 Correlated colour temperature ........................................................................................................ 4
7 Sources for realizing CIE standard illuminants .......................................................................... 4
7.1 Source for CIE standard illuminant A ............................................................................................. 4
7.2 Sources 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 .................................................................................................................... 9
Annex C (informative) History of CIE standard illuminant A ............................................................ 17
Bibliography ....................................................................................................................................................... 18
© ISO/CIE 2021 – All rights reserved iii---------------------- Page: 5 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(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
ISO/TC 274 “Light and Lighting”.This first edition of ISO/CIE 11664-2 cancels and replaces ISO 11664-2:2007/CIE S 014-2:2006, which
has been technically revised.The main changes compared to the previous edition are as follows:
— CIE illuminant D50 has been included as CIE standard illuminant in this document 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 ISO website and CIE website.
Any feedback or questions on this document should be directed to the CIE Central Bureau or to the user’s
national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.
iv © ISO/CIE 2021 – All rights reserved---------------------- Page: 6 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(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 D65CIE 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 D illuminants, and illuminants for LED and other
electric light sources. These illuminants are described in Publication 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 defined in this
document. Data and guidelines that facilitate such practice are provided in Publication 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 sky. 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.© ISO/CIE 2021 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
---------------------- Page: 8 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
DRAFT INTERNATIONAL STANDARD ISO/CIE DIS 11664-2.2:2021(E)
Colorimetry — Part 2: CIE standard illuminants
1 Scope
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 Normative 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 VocabularyISO 23603/CIE S 012, Standard method of assessing the spectral quality of daylight simulators for visual
appraisal and measurement of colourBIPM The International System of Units (SI), 9 edition, published on May 20, 2019
3 Terms and definitionsFor the purposes of this document, the terms and definitions given in CIE S 017 and the following apply.
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/
3.1
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]
3.2
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 2021 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
3.3
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]
3.4
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]
3.5
standard air
dry air at 15 °C and 101 325 Pa, containing 0,045 % by volume of carbon dioxide
Note 1 to entry: This definition is intended for this document only.
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)
over the wavelength range 300 nm to 830 nm.1,435×10
exp −1
560 2848×560
S (λ ) 100 × (1)
A
1,435×10
exp −1
2848λ
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 1 Table A.1 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).Note 2 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 the expression
MT(,λ )
e,λ
S (λ )= 100 , (2)
MT(560, )
e,λ
where
2 © ISO/CIE 2021 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
c
−5 2
M (λ ,T ) c λ exp−1 , (3)
e,λ 1
λ T
λ is the wavelength (in nm),
and the quotient c /T is given by
c 14 350 μm⋅×K 1,435 10
nm . (4)
T 2 848 K 2 848
Since the numerical value of c cancels out of 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 defined in
1 2Formula (4).
With the value of c as defined in (BIPM, The International System of Units (SI), 9th edition), 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 B.5 CIE standard illuminant D65
5.1 Definition
CIE standard illuminant D65 is defined 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 basis
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 and
830 nm, as reported by Judd, MacAdam, and Wyszecki (Judd et al., 1964). The extrapolated values are
believed to be sufficiently accurate for conventional colorimetric purposes, but are not recommended for
non-colorimetric use.5.3 Correlated colour temperature
CIE standard illuminant D65 has a nominal correlated colour temperature of 6 500 K.
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, specified in the International System of Units (SI), 9th edition (2019), 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.© ISO/CIE 2021 – All rights reserved 3
---------------------- Page: 11 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
6 CIE standard illuminant D50
6.1 Definition
CIE standard illuminant D50 is defined 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 Correlated colour temperature
CIE standard illuminant D50 has a nominal correlated colour temperature of 5 000 K.
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, specified in the International System
of Units (SI), 9th edition (2019), 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.
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 Sources for realizing CIE standard illuminants
7.1 Source 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 temperature2 848 K⋅c
T= (7)
14 350 μm⋅K
on a radiation temperature scale specified by a given value of the second radiation constant c 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 value of c is 14 387,768 775 … µm·K and thus the assigned temperature of CIE standard source A is
given by14 387,768 775 ... μm⋅K
T ×=2 848 K 2 855,496 ... K≈ 2 855,5 K (8)
14 350 μm⋅K
7.2 Sources 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
D50 can be assessed by a method described in ISO 23603/CIE S 012.4 © ISO/CIE 2021 – All rights reserved
---------------------- Page: 12 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(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)S (λ) S (λ) S (λ) S (λ)
λ/nm λ/nm λ/nm λ/nm
A A A A
300 0,930 483 334 3,006 78 368 7,462 92 402 15,273 6
301 0,967 643 335 3,098 61 369 7,640 66 403 15,561 6
302 1,005 97 336 3,192 53 370 7,821 35 404 15,853 0
303 1,045 49 337 3,288 57 371 8,005 01 405 16,148 0
304 1,086 23 338 3,386 76 372 8,191 67 406 16,446 4
305 1,128 21 339 3,487 12 373 8,381 34 407 16,748 4
306 1,171 47 340 3,589 68 374 8,574 04 408 17,053 8
307 1,216 02 341 3,694 47 375 8,769 80 409 17,362 8
308 1,261 88 342 3,801 52 376 8,968 64 410 17,675 3
309 1,309 10 343 3,910 85 377 9,170 56 411 17,991 3
310 1,357 69 344 4,022 50 378 9,375 61 412 18,310 8
311 1,407 68 345 4,136 48 379 9,583 78 413 18,633 9
312 1,459 10 346 4,252 82 380 9,795 10 414 18,960 5
313 1,511 98 347 4,371 56 381 10,009 6 415 19,290 7
314 1,566 33 348 4,492 72 382 10,227 3 416 19,624 4
315 1,622 19 349 4,616 31 383 10,448 1 417 19,961 7
316 1,679 59 350 4,742 38 384 10,672 2 418 20,302 6
317 1,738 55 351 4,870 95 385 10,899 6 419 20,647 0
318 1,799 10 352 5,002 04 386 11,130 2 420 20,995 0
319 1,861 27 353 5,135 68 387 11,364 0 421 21,346 5
320 1,925 08 354 5,271 89 388 11,601 2 422 21,701 6
321 1,990 57 355 5,410 70 389 11,841 6 423 22,060 3
322 2,057 76 356 5,552 13 390 12,085 3 424 22,422 5
323 2,126 67 357 5,696 22 391 12,332 4 425 22,788 3
324 2,197 34 358 5,842 98 392 12,582 8 426 23,157 7
325 2,269 80 359 5,992 44 393 12,836 6 427 23,530 7
326 2,344 06 360 6,144 62 394 13,093 8 428 23,907 2
327 2,420 17 361 6,299 55 395 13,354 3 429 24,287 3
328 2,498 14 362 6,457 24 396 13,618 2 430 24,670 9
329 2,578 01 363 6,617 74 397 13,885 5 431 25,058 1
330 2,659 81 364 6,781 05 398 14,156 3 432 25,448 9
331 2,743 55 365 6,947 20 399 14,430 4 433 25,843 2
332 2,829 28 366 7,116 21 400 14,708 0 434 26,241 1
333 2,917 01 367 7,288 11 401 14,989 1 435 26,642 5
© ISO/CIE 2021 – All rights reserved 5
---------------------- Page: 13 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
S (λ) S (λ) S (λ) S (λ)
λ/nm λ/nm λ/nm λ/nm
A A A A
436 27,047 5 480 48,242 3 524 75,127 5 568 105,741
437 27,456 0 481 48,796 3 525 75,790 3 569 106,462
438 27,868 1 482 49,353 3 526 76,455 1 570 107,184
439 28,283 6 483 49,913 2 527 77,121 7 571 107,906
440 28,702 7 484 50,476 0 528 77,790 2 572 108,630
441 29,125 3 485 51,041 8 529 78,460 5 573 109,354
442 29,551 5 486 51,610 4 530 79,132 6 574 110,078
443 29,981 1 487 52,181 8 531 79,806 5 575 110,803
444 30,414 2 488 52,756 1 532 80,482 1 576 111,529
445 30,850 8 489 53,333 2 533 81,159 5 577 112,255
446 31,290 9 490 53,913 2 534 81,838 6 578 112,982
447 31,734 5 491 54,495 8 535 82,519 3 579 113,709
448 32,181 5 492 55,081 3 536 83,201 7 580 114,436
449 32,632 0 493 55,669 4 537 83,885 6 581 115,164
450 33,085 9 494 56,260 3 538 84,571 2 582 115,893
451 33,543 2 495 56,853 9 539 85,258 4 583 116,622
452 34,004 0 496 57,450 1 540 85,947 0 584 117,351
453 34,468 2 497 58,048 9 541 86,637 2 585 118,080
454 34,935 8 498 58,650 4 542 87,328 8 586 118,810
455 35,406 8 499 59,254 5 543 88,021 9 587 119,540
456 35,881 1 500 59,861 1 544 88,716 5 588 120,270
457 36,358 8 501 60,470 3 545 89,412 4 589 121,001
458 36,839 9 502 61,082 0 546 90,109 7 590 121,731
459 37,324 3 503 61,696 2 547 90,808 3 591 122,462
460 37,812 1 504 62,312 8 548 91,508 2 592 123,193
461 38,303 1 505 62,932 0 549 92,209 5 593 123,924
462 38,797 5 506 63,553 5 550 92,912 0 594 124,655
463 39,295 1 507 64,177 5 551 93,615 7 595 125,386
464 39,796 0 508 64,803 8 552 94,320 6 596 126,118
465 40,300 2 509 65,432 5 553 95,026 7 597 126,849
466 40,807 6 510 66,063 5 554 95,733 9 598 127,58
467 41,318 2 511 66,696 8 555 96,442 3 599 128,312
468 41,832 0 512 67,332 4 556 97,151 8 600 129,043
469 42,349 1 513 67,970 2 557 97,862 3 601 129,774
470 42,869 3 514 68,610 2 558 98,573 9 602 130,505
471 43,392 6 515 69,252 5 559 99,286 4 603 131,236
472 43,919 2 516 69,896 9 560 100,000 604 131,966
473 44,448 8 517 70,543 5 561 100,715 605 132,697
474 44,981 6 518 71,192 2 562 101,430 606 133,427
475 45,517 4 519 71,843 0 563 102,146 607 134,157
476 46,056 3 520 72,495 9 564 102,864 608 134,887
477 46,598 3 521 73,150 8 565 103,582 609 135,617
478 47,143 3 522 73,807 7 566 104,301 610 136,346
479 47,691 3 523 74,466 6 567 105,020 611 137,075
6 © ISO/CIE 2021 – All rights reserved
---------------------- Page: 14 ----------------------
oSIST prEN ISO/CIE 11664-2:2021
ISO/CIE DIS 11664-2.2:2021(E)
S (λ) S (λ) S (λ) S (λ)
λ/nm λ/nm λ/nm λ/nm
A A A A
612 137,804 656 169,203 700 198,261 744 223,826
613 138,532 657 169,895 701 198,884 745 224,361
614 139,260 658 170,586 702 199,506 746 224,893
615 139,988 659 171,275 703 200,125 747 225,423
616 140,715 660 171,963 704 200,743 748 225,951
617 141,441 661 172,650 705 201,359 749 226,477
618 142,167 662 173,335 706 201,972 750 227,000
619 142,893 663 174,019 707 202,584 751 227,522
620 143,618 664 174,702 708 203,195 752 228,041
621 144,343 665 175,383 709 203,803 753 228,558
622 145,067 666 176,063 710 204,409 754 229,073
623 145,790 667 176,741 711 205,013 755 229,585
624 146,513 668 177,419 712 205,616 756 230,096
625 147,235 669 178,094 713 206,216 757 230,604
626 147,957 670 178,769 714 206,815 758 231,110
627 148,678 671 179,441 715 207,411 759 231,614
628 149,398 672 180,113 716 208,006 760 232,115
629 150,117 673 180,783 717 208,599 761 232,615
630 150,836 674 181,451 718 209,189 762 233,112
631 151,554 675 182,118 719 209,778 763 233,606
632 152,271 676 182,783 720 210,365 764 234,099
633 152,988 677 183,447 721 210,949 765 234,589
634 153,704 678 184,109 722 211,532 766 235,078
635 154,418 679 184,770 723 212,112 767 235,564
636 155,132 680 185,429 724 212,691 768 236,047
637 155,845 681 186,087 725 213,268 769 236,529
638 156,558 682 186,743 726 213,842 770 237,008
639 157,269 683 187,397 727 214,415 771 237,485
640 157,979 684 188,050 728 214,985 772 237,959
641 158,689 685 188,701 729 215,553 773 238,432
642 159,397 686 189,350 730 216,120 774 238,902
643 160,104 687 189,998 731 216,684 775 239,370
644 160,811 688 190,644 732 217,246 776 239,836
645 161,516 689 191,288 733 217,806 777 240,299
646 162,221 690 191,931 734 218,364 778 240,760
647 162,924 691 192,572 735 218,920 779 241,219
...
SLOVENSKI STANDARD
oSIST prEN ISO/CIE 11664-2:2020
01-april-2020
Kolorimetrija - 2. del: Standardizirana osvetljevala (iluminanti) CIE (ISO/CIE DIS
11664-2:2020)Colorimetry - Part 2: CIE standard illuminants (ISO/CIE DIS 11664-2:2020)
Farbmetrik - Teil 2: CIE Normlichtarten (ISO/CIE DIS 11664-2:2020)
Colorimétrie - Partie 2: Illuminants CIE normalisés (ISO/CIE DIS 11664-2:2020)
Ta slovenski standard je istoveten z: prEN ISO/CIE 11664-2
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
oSIST prEN ISO/CIE 11664-2:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------oSIST prEN ISO/CIE 11664-2:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
DRAFT INTERNATIONAL STANDARD
ISO/CIE DIS 11664-2
CIE Secretariat: CIE
Voting begins on: Voting terminates on:
2020-02-13 2020-05-07
Colorimetry —
Part 2:
CIE standard illuminants
Colorimétrie —
Partie 2: Illuminants CIE normalisés
ICS: 17.180.20
Member bodies are requested to consult relevant national interests in ISO/TC
274 before casting their ballot to the e-Balloting application.
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/CIE DIS 11664-2:2020(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO/CIE 2020
---------------------- Page: 3 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/CIE 2020
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.ISO copyright office CIE Central Bureau
CP 401 • Ch. de Blandonnet 8 Babenbergerstraße 9/9A
CH-1214 Vernier, Geneva A-1010 Vienna, Austria
Phone: +41 22 749 01 11 Phone: +43 1 714 3187
Fax: +41 22 749 09 47 Fax: +41 22 749 09 47
Email: copyright@iso.org Email: ciecb@cie.co.at
Website: www.iso.org Website: www.cie.co.at
Published in Switzerland
ii © ISO/CIE 2020 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
Contents
Foreword ......................................................................................................................................................................... iv
Introduction..................................................................................................................................................................... v
1 Scope .................................................................................................................................................................... 1
2 Normative references .................................................................................................................................... 1
3 Terms and definitions.................................................................................................................................... 1
4 CIE standard illuminant A ............................................................................................................................ 4
4.1 Definition ............................................................................................................................................................ 4
4.2 Theoretical basis ............................................................................................................................................. 4
4.3 Supplementary notes ..................................................................................................................................... 5
5 CIE standard illuminant D65 ....................................................................................................................... 5
5.1 Definition ............................................................................................................................................................ 5
5.2 Experimental basis ......................................................................................................................................... 6
5.3 Correlated colour temperature .................................................................................................................. 6
6 CIE standard illuminant D50 ....................................................................................................................... 6
6.1 Definition ............................................................................................................................................................ 6
6.2 Correlated colour temperature .................................................................................................................. 6
7 Sources for realizing CIE standard illuminants .................................................................................... 7
7.1 Source for CIE standard illuminant A ....................................................................................................... 7
7.2 Sources for CIE standard illuminants D65 and D50 ............................................................................ 7
Annex A (normative) Table of relative spectral power distributions of CIE standard
illuminants A, D65 and D50 ......................................................................................................................... 8
Bibliography ................................................................................................................................................................. 15
© ISO/CIE 2020 – All rights reserved iii---------------------- Page: 5 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(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
ISO/TC 274.This first edition of ISO/CIE 11664-2 cancels and replaces ISO 11664-2:2007/CIE S 014-2:2006, of which
it constitutes a minor revision, incorporating minor editorial updates.A list of all parts in the ISO/CIE 11664 series can be found on the ISO website and CIE website.
Any feedback or questions on this document should be directed to the CIE Central Bureau or to the user’s
national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.
iv © ISO/CIE 2020 – All rights reserved---------------------- Page: 6 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(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 2 856 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 D65CIE 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 and other D illuminants. These illuminants are described
in Publication 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 defined in this
document. Data and guidelines that facilitate such practice are provided in Publication 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 sky. 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.For laboratory realizations of CIE standard illuminant A, a CIE standard source, the CIE standard source
A, is described in this document. At present, there are no CIE recommended sources representing CIE
standard illuminants D65 and D50.© ISO/CIE 2020 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
---------------------- Page: 8 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
Colorimetry — Part 2: CIE standard illuminants
1 Scope
This document specifies 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 Normative 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
ISO 23603/CIE S 012 Standard method of assessing the spectral quality of daylight simulators for
visual appraisal and measurement of colourBIPM The International System of Units (SI), 9 edition, published on May 20, 2019
3 Terms and definitionsFor the purposes of this document, the terms and definitions given in CIE S 017 and the following
apply.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/
3.1
chromaticity coordinates, pl
coordinates expressing the ratios of each of a set of three tristimulus values to their sum
Note 1 to entry: As the sum of the three chromaticity coordinates equals 1, two of them are sufficient to
define a chromaticity.Note 2 to entry: In the CIE 1931 and 1964 standard colorimetric systems, the chromaticity coordinates are
represented by the symbols x, y, z and x , y , z .10 10 10
Note 3 to entry: The chromaticity coordinates are a quantity of unit one.
© ISO/CIE 2020 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
[SOURCE: CIE S 017:– , entry 17-23-053]
3.2
chromaticity diagram
plane diagram in which points specified by chromaticity coordinates represent the chromaticities
of colour stimuliNote 1 to entry: In the CIE standard colorimetric systems y is normally plotted as ordinate and x as abscissa,
to obtain an x, y chromaticity diagram.[SOURCE: CIE S 017:– , entry 17-23-054]
3.3
CIE standard illuminant
illuminant standardized by the CIE for the purpose of harmonization
[SOURCE: CIE S 017:– , entry 17-23-021, modified – notes to entry omitted]
3.4
CIE standard source
artificial source specified by the CIE whose radiation approximates a CIE standard illuminant
[SOURCE: CIE S 017:– , entry 17-23-022, modified – notes to entry omitted]3.5
CIE 1976 uniform chromaticity scale diagram
CIE 1976 UCS diagram
uniform chromaticity scale diagram produced by plotting in rectangular coordinates v against u,
quantities defined by the equationsu = 4 X / (X + 15 Y + 3 Z) = 4 x / (−2 x + 12 y + 3)
v = 9 Y / (X + 15 Y + 3 Z) = 9 y / (−2 x + 12 y + 3)
where X, Y, Z are the tristimulus values in the CIE 1931 or 1964 standard colorimetric systems,
and x, y are the corresponding chromaticity coordinates of the colour stimulus considered
Note 1 to entry: The CIE 1976 uniform-chromaticity-scale diagram is a modification of, and supersedes, the
CIE 1960 UCS diagram in which v was plotted against u in rectangular coordinates. The relationships
between the two pairs of coordinates are: u = u; v = 1,5 v.[SOURCE: CIE S 017:– , entry 17-23-073]
3.6
colour temperature
temperature of a Planckian radiator whose radiation has the same chromaticity as that of a given
stimulusNote 1 to entry: The colour temperature is expressed in kelvin (K).
[SOURCE: CIE S 017:– , entry 17-23-067]
Under preparation. Stage at the time of publication: CIE DIS 017:2016
2 © ISO/CIE 2020 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
3.7
correlated colour temperature
CCT
temperature of a Planckian radiator having the chromaticity nearest the chromaticity associated
with the given spectral distribution on a modified 1976 UCS diagram where u, 2/3v are the
coordinates of the Planckian locus and the test stimulusNote 1 to entry: The concept of correlated colour temperature should not be used if the chromaticity of the
test source differs more than from the Planckian radiator, whereΔC = u −u + v −v =510
( ) ( )
t p t p
uv, refer to the test source, uv, to the Planckian radiator.
tt pp
Note 2 to entry: Correlated colour temperature can be calculated by a simple minimum search computer
program that searches for that Planckian temperature that provides the smallest chromaticity difference
between the test chromaticity and the Planckian locus, or e.g. by a method recommended by Robertson, A.R.
“Computation of correlated color temperature and distribution temperature”, J. Opt. Soc. Am. 58, 1528-
1535, 1968.(Note that the values in some of the tables in this reference are not up-to-date).
Note 3 to entry: The correlated colour temperature is expressed in kelvin (K).[SOURCE: IEC 60050-845:– , Term 17-23-068]
3.8
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:– , entry 17-23-020]
3.9
illuminant
radiation with a relative spectral power distribution defined over the wavelength range that
influences object colour perception[SOURCE: CIE S 017:– , entry 17-23-018, Note 1 to entry omitted.]
3.10
Planckian radiator
blackbody
ideal thermal radiator that absorbs completely all incident radiation, whatever the wavelength,
the direction of incidence or the polarizationNote 1 to entry: A Planckian radiator has, for any wavelength and any direction, the maximum spectral
distribution of radiance for a thermal radiator in thermal equilibrium at a given temperature.
[SOURCE: CIE S 017:– , entry 17-24-004]Under preparation. Stage at the time of publication: IEC CDV 60050-845:2018.
Under preparation. Stage at the time of publication: CIE DIS 017:2016
© ISO/CIE 2020 – All rights reserved 3
---------------------- Page: 11 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
3.11
Planckian locus
locus of points in a chromaticity diagram that represents chromaticities of the radiation of
Planckian radiators at different temperatures[SOURCE: CIE S 017:– , entry 17-23-059]
3.12
tristimulus values, pl
amounts of the three reference colour stimuli, in a given trichromatic system, required to match
the colour of the stimulus consideredNote 1 to entry: In the CIE standard colorimetric systems, the tristimulus values are represented, for
example, by the symbols R, G, B; X, Y, Z; R10, G10, B10;or X10, Y10, Z10.[SOURCE: CIE S 017:– , entry 17-23-038]
4 CIE standard illuminant A
4.1 Definition
When CIE standard illuminant A is referred, the relative power distribution values provided in
Table A.1 shall be used. If required, other intermediate values may be derived by linear
interpolation from the published values. The relative spectral power distribution of CIE standard
illuminant A, S (), is defined by the equation1,43510
exp −1
560 2 848 560
S ()=100 (1)
A
1,43510
exp −1
2 848
where 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. This spectral
power distribution is normalized to the value 100 (exactly) at the wavelength 560 nm (exactly).
CIE standard illuminant A is defined over the 300 nm to 830 nm spectral region.Note 1 Table A.1 provides the relative spectral power distribution of CIE standard illuminant A between
300 nm and 830 nm to six significant digits, at 1 nm intervals. For all practical purposes it suffices to use
these tabulated values instead of the values calculated from Equation (1).Note 2 Despite the fact that Equation (1) is based on Planck's equation for vacuum, the wavelengths are
to be taken as being in standard air (dry air at 15 ºC and 101 325 Pa, containing 0,03 % by volume of carbon
dioxide). This makes CIE standard illuminant A compatible with other CIE colorimetric and photometric
data.4.2 Theoretical basis
Equation (1) is equivalent to and can be derived from the expression
S() = 100 M (,T) / M (560, T), (2)
e, e,
where
Under preparation. Stage at the time of publication: CIE DIS 017:2016
4 © ISO/CIE 2020 – All rights reserved
---------------------- Page: 12 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
−5 −1
M (,T) = c [exp(c / T) − 1] , (3)
e, 1 2
is the wavelength (in nm),
and the ratio c /T is given by
c /T = 1,435 10 / 2 848 nm. (4)
Since the numerical value of c cancels out of Equation (2), this definition of CIE standard
illuminant A involves no assumptions about the numerical values of c , c , and T other than the
1 2ratio defined in Equation (4).
4.3 Supplementary notes
CIE standard illuminant A was originally defined in 1931 (CIE, 1931) as the relative spectral
power distribution of a Planckian radiator of temperatureT = 2 848 K, (5)
CIE 1931
the value of the second radiation constant c then being taken as
c = 14 350 µm·K. (6)
2, CIE 1931
The form of definition as given in Equation (1) was carefully chosen to ensure that CIE standard
illuminant A was defined as a relative spectral power distribution and not as a function of
temperature. As explained in 4.2 above, the definition of the relative spectral power distribution
has not changed since 1931 and Equation (1) simply expresses it in a general form.
What has changed is the temperature assigned to this distribution. The value of c given in
Equation (6) and used by the CIE in 1931 is different from the respective values that were assigned
to this constant in the International Temperature Scales (ITS) or International Practical
Temperature Scales (IPTS) of 1927 (c = 14 320 µmK), 1948 (c = 14 380 µm·K), 1968
2,ITS-27 2,IPTS-48and 1990 (c = c = 14 388 µm·K). The revised International System of Units (SI) (BIPM,
2,IPTS-68 2,ITS-90The International System of Units (SI), 9th edition) has fixed the value of the Planck constant,
which changes the value of c to 1,438 776 877 5.. 10 m·K. Although this has had no effect on
the relative spectral power distribution of CIE standard illuminant A, the correlated colour
temperatures of sources recommended for laboratory realizations have been different over the
years, depending on the values of c used.As may be seen from Equation (4), the colour temperatures associated with CIE standard
illuminant A on the various international temperature scales referred to above were T =
ITS-272 842 K, T = 2 854 K, and T = T = 2 856 K, respectively (see also 7.1). The assigned
IPTS-48 IPTS-68 ITS-90temperature for CIE standard illuminant A is 2855,496 K, thus proximately 2855,5 K.
5 CIE standard illuminant D655.1 Definition
When CIE standard illuminant D65 is referred, the relative spectral power distribution values
provided in Table A.1 shall be used. 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 may be derived by linear interpolation from the published
values. 5Information on the procedure used to derive D65 values is given in CIE 15.
© ISO/CIE 2020 – All rights reserved 5
---------------------- Page: 13 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
5.2 Experimental basis
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 and 830 nm, as reported by Judd, MacAdam, and Wyszecki (Judd et al., 1964). The
extrapolated values are believed to be sufficiently accurate for conventional colorimetric
purposes, but are not recommended for non-colorimetric use.5.3 Correlated colour temperature
CIE standard illuminant D65 has a nominal correlated colour temperature of 6 500 K. The exact
value depends on the convention used to assign a correlated colour temperature to a stimulus
whose chromaticity, as in this case, does not fall precisely on the Planckian locus.
NOTE 1 Using the value of c = 14 388 m·K, specified in the International Temperature Scale of 1990,
the definition given in 0, and the relative spectral power distribution data of Table A.1, the correlated colour
temperature of CIE standard illuminant D65 is found to be 6 503,616 K . The difference from the nominal
correlated colour temperature of 6 500 K of CIE standard illuminant D65 is judged to be visually
insignificant.NOTE 2 In the case when, instead of the data represented in Table A.1, a calculation method as
recommended in CIE 015 is chosen, the correct rounding of the constants used in the calculations to
reproduce the tabulated data is important.6 CIE standard illuminant D50
6.1 Definition
When CIE standard illuminant D50 is referred, the relative power distribution values provided in
Table A.1 shall be used. 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 may be derived by linear interpolation from the published values.
6.2 Correlated colour temperatureCIE standard illuminant D50 has a nominal correlated colour temperature of 5 000 K. The exact
value depends on the convention used to assign a correlated colour temperature to a stimulus
whose chromaticity, as in this case, does not fall precisely on the Planckian locus.
NOTE 1 Using the value of c = 14 388 m·K specified in the International Temperature Scale of 1990,
the definition given in 0, and the relative spectral power distribution data of Table A.1, the correlated colour
temperature of CIE standard illuminant D50 is found to be 5 002,782 K. The difference from the nominal
correlated colour temperature of 5 000 K of CIE standard illuminant D50 is judged to be visually
insignificant.NOTE 2 In the case when, instead of the data represented in Table A.1, a calculation method as
recommended in CIE 015 is chosen, the correct rounding of the constants used in the calculations to
reproduce the tabulated data is important.6 © ISO/CIE 2020 – All rights reserved
---------------------- Page: 14 ----------------------
oSIST prEN ISO/CIE 11664-2:2020
ISO/CIE DIS 11664-2:2020(E)
7 Sources for realizing CIE standard illuminants
7.1 Source 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 a correlated colour temperature2 848 Kc
T = (7)
14 350 μmK
on a radiation temperature scale specified by a given value of the second radiation constant c in
m·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 value of c is 14 387,768 775 … µm·K and thus the correlated colour temperature of CIE
standard source A is given by14 387,768 775 ... μmK
TK= 2 848 K= 2 855,496 ... 2 855,5 K (8)
14 350 μmK
Sources related to earlier temperature scales may have to be recalibrated.
7.2 Sources 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 D50 can be assessed b...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.