SIST EN ISO/CIE 11664-1:2019

SLOVENSKI STANDARD
oSIST prEN ISO/CIE 11664-1:2019
01-marec-2019
.RORULPHWULMDGHO6WDQGDUGL]LUDQLEDUYQRPHWULþQLRSD]RYDOHF&,(,62&,()',6

Colorimetry - Part 1: CIE standard colorimetric observers (ISO/CIE/FDIS 11664-1:2019)
Farbmetrik - Teil 1: CIE farbmetrische Normalbeobachter (ISO/CIE/FDIS 11664-1:2019)
Colorimétrie - Partie 1: Observateurs CIE de référence pour la colorimétrie
(ISO/CIE/FDIS 11664-1:2019)
Ta slovenski standard je istoveten z: prEN ISO/CIE 11664-1
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
oSIST prEN ISO/CIE 11664-1:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO/CIE 11664-1:2019
FINAL
INTERNATIONAL ISO/CIE
DRAFT
STANDARD FDIS
11664-1
CIE
Colorimetry —
Secretariat: ISO secretariat
Voting begins on:
Part 1:
2019-01-29
CIE standard colorimetric observers
Voting terminates on:
2019-04-23
Colorimétrie —
Partie 1: Observateurs CIE de référence pour la colorimétrie
Member bodies are requested to consult relevant national interests in ISO/TC
274 before casting their ballot to the e-Balloting application.
ISO/CEN PARALLEL PROCESSING
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 SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/CIE FDIS 11664-1:2019(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO/CIE 2019

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COPYRIGHT PROTECTED DOCUMENT
© ISO/CIE 2019
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
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Published in Switzerland
ii © ISO/CIE 2019 – All rights reserved

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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Specifications . 4
4.1 Colour-matching functions . 4
4.2 Spectral chromaticity coordinates . 5
5 Derivation of the colour-matching functions for the CIE 1931 standard colorimetric
observer . 5
5.1 Experimental basis . 5
5.2 Transformation procedures . 5
5.3 Transformation properties . 6
5.4 Comparison with earlier data . 6
6 Derivation of the colour-matching functions for the CIE 1964 standard colorimetric
observer . 7
6.1 Experimental basis . 7
6.2 Transformation procedures . 7
6.3 Transformation properties . 7
6.4 Comparison with earlier data . 7
7 Practical application of colour-matching functions for CIE standard colorimetric
observers . 8
7.1 Obtaining tristimulus values . 8
7.2 The basis for integration . 8
7.3 Rod activity. 9
7.4 The use of restricted data . 9
7.5 Standard of reflectance . 9
Bibliography .33
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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 11664-1 cancels and replaces ISO 11664-1:2007/CIE S 014-1:2006, 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.
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 2019 – All rights reserved

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Introduction
Colours with different spectral compositions can look alike. An important function of colorimetry is to
determine whether a pair of such metameric colours will look alike. The use of visual colorimeters for
this purpose is handicapped by variations in the colour matches made among observers classified as
having normal colour vision. Visual colorimetry also tends to be time-consuming. For these reasons, it
has long been the practice in colorimetry to make use of sets of colour-matching functions to calculate
tristimulus values for colours: equality of tristimulus values for a pair of colours indicates that the colour
appearances of the two colours match, when they are viewed in the same conditions by an observer
for whom the colour-matching functions apply. The use of standard sets of colour-matching functions
makes the comparison of tristimulus values obtained at different times and locations possible.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/CIE FDIS 11664-1:2019(E)
Colorimetry —
Part 1:
CIE standard colorimetric observers
1 Scope
This document specifies colour-matching functions for use in colorimetry. Two sets of colour-matching
functions are specified.
a) Colour-matching functions for the CIE 1931 standard colorimetric observer.
This set of colour-matching functions is representative of the colour-matching properties of
observers with normal colour vision for visual field sizes of angular subtense from about 1° to
about 4°, for vision at photopic levels of adaptation.
b) Colour-matching functions for the CIE 1964 standard colorimetric observer.
This set of colour-matching functions is representative of the colour-matching properties of
observers with normal colour vision for visual field sizes of angular subtense greater than about
4°, for vision at sufficiently high photopic levels and with spectral power distributions such that no
participation of the rod receptors of the retina is to be expected.
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
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 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
colour stimulus function
φ (λ)
λ
description of a colour stimulus by the spectral distribution of a radiometric quantity, such as radiance
or radiant power, as a function of wavelength
[SOURCE: CIE DIS 017:2016, Term 17-23-003]
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3.2
metameric colour stimuli, pl
metamers, pl
spectrally different colour stimuli that have the same tristimulus values in a specified colorimetric system
Note 1 to entry: The corresponding property is called “metamerism”.
[SOURCE: CIE DIS 017:2016, Term 17-23-008]
3.3
monochromatic stimulus
spectral stimulus
stimulus consisting of monochromatic radiation
[SOURCE: CIE DIS 017:2016, Term 17-23-011]
3.4
equi-energy spectrum
spectrum of radiation whose spectral distribution of a radiometric quantity as a function of wavelength
is constant throughout the visible region
Note 1 to entry: The radiation of the equi-energy spectrum is sometimes regarded as an illuminant, in which case
it is denoted by the symbol E.
[SOURCE: CIE DIS 017:2016, Term 17-23-023, modified — “(φ (λ) = constant)” at the end of the definition
λ
omitted.]
3.5
additive mixture
stimulation that combines on the retina the actions of various colour stimuli in such a
manner that they cannot be perceived individually
[SOURCE: CIE DIS 017:2016, Term 17-23-030]
3.6
colour matching
action of making a colour stimulus appear the same in colour as a given colour stimulus
[SOURCE: CIE DIS 017:2016, Term 17-23-031]
3.7
trichromatic system
system for specifying colour stimuli in terms of tristimulus values, based on matching colours by
additive mixture of three suitably chosen reference colour stimuli
[SOURCE: CIE DIS 017:2016, Term 17-23-036]
3.8
reference colour stimuli, pl
set of three colour stimuli on which a trichromatic system is based
Note 1 to entry: These stimuli are either real colour stimuli or theoretical stimuli which are defined by linear
combinations of real colour stimuli.
Note 2 to entry: In the CIE standard colorimetric systems, the reference colour stimuli are represented by the
symbols [R], [G], [B], [X], [Y], [Z], [R ], [G ], [ ] and [X ], [Y ], [Z ].
10 10 B10 10 10 10
[SOURCE: CIE DIS 017:2016, Term 17-23-037]
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3.9
tristimulus values, pl
amount of the three reference colour stimuli, in a given trichromatic system,
required to match the colour of the stimulus considered
Note 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; R , G , B or X , Y , Z .
10 10 10 10 10 10
[SOURCE: CIE DIS 017:2016, Term 17-23-038]
3.10
colour-matching functions, pl
tristimulus values of monochromatic stimuli of equal radiant flux
[SOURCE: CIE DIS 017:2016, Term 17-23-039, modified — Notes to entry omitted.]
3.11
CIE 1931 standard colorimetric system
X, Y, Z
system for determining the tristimulus values of any spectral power distribution using the set of
reference colour stimuli [X], [Y], [Z], and the three CIE colour-matching functions xyλλ,,z λ
() () ()
adopted by the CIE in 1931
Note 1 to entry: y()λ is identical to V(λ) and hence the tristimulus values Y are proportional to values of
luminance.
Note 2 to entry: The CIE 1931 standard colorimetric system is applicable to centrally viewed fields of angular
subtense between about 1° and about 4° (0,017 rad and 0,07 rad).
Note 3 to entry: The CIE 1931 standard colorimetric system can be derived from the CIE 1931 RGB colorimetric
system using a transformation based on a set of three linear equations. The CIE 1931 RGB system is based on
three real monochromatic reference stimuli.
Note 4 to entry: See also CIE 15 Colorimetry.
[SOURCE: CIE DIS 017:2016, Term 17-23-045]
3.12
CIE 1964 standard colorimetric system
X , Y , Z
10 10 10
system for determining the tristimulus values of any spectral power distribution using the set of
reference colour stimuli [X ], [Y ], [Z ], and the three CIE colour-matching functions
10 10 10
xyλλ,,z λ adopted by the CIE in 1964
() () ()
10 10 10
Note 1 to entry: The CIE 1964 standard colorimetric system is applicable to centrally viewed fields of angular
subtense greater than about 4° (0,07 rad).
Note 2 to entry: When the CIE 1964 standard colorimetric system is used, all symbols that represent colorimetric
measures are distinguished by use of the subscript 10.
Note 3 to entry: See also CIE 15 Colorimetry.
[SOURCE: CIE DIS 017:2016, Term 17-23-046]
3.13
CIE colour-matching functions, pl
functions xyλλ,,z λ in the CIE 1931 standard colorimetric system or xyλλ,,z λ in
() () () () () ()
10 10 10
the CIE 1964 standard colorimetric system
[SOURCE: CIE DIS 017:2016, Term 17-23-047]
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3.14
CIE 1931 standard colorimetric observer
ideal observer whose colour-matching properties correspond to the CIE colour-matching functions
xy()λλ,,() z()λ adopted by the CIE in 1931
[SOURCE: CIE DIS 017:2016, Term 17-23-049]
3.15
CIE 1964 standard colorimetric observer
ideal observer whose colour-matching properties correspond to the CIE colour-matching functions
xyλλ,,z λ adopted by the CIE in 1964
() () ()
10 10 10
[SOURCE: CIE DIS 017:2016, Term 17-23-050, modified — Note 1 to entry omitted.]
3.16
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 is equal to 1, two of them are sufficient to
define a chromaticity.
Note 2 to entry: In the CIE standard colorimetric systems, the chromaticity coordinates are represented by the
symbols x, y, z or x , y , z .
10 10 10
Note 3 to entry: The chromaticity coordinates are a quantity of unit one.
[SOURCE: CIE DIS 017:2016, Term 17-23-053]
3.17
spectral chromaticity coordinates, pl
r(λ), g(λ), b(λ); x(λ), y(λ), z(λ); r (λ), g (λ), b (λ); x (λ), y (λ), z (λ)
10 10 10 10 10 10
chromaticity coordinates of monochromatic stimuli
[SOURCE: CIE DIS 017:2016, Term 17-23-055]
3.18
spectral luminous efficiency
V(λ), ; V′(λ), ; V (λ), ; V (λ), mes;m 10
the CIE 10° photopic photometric observer>; V (λ), M
efficiency function for photopic vision>
quotient of the radiant flux at wavelength λ and that at
m
wavelength λ, such that both produce equally intense luminous sensations for a specified photometric
condition and λ is chosen so that the maximum value of this quotient is equal to 1
m
[SOURCE: CIE DIS 017:2016, Term 17-21-035, modified — Notes to entry omitted.]
3.19
perfect reflecting diffuser
ideal isotropic diffuser with a reflectance equal to unity
4 Specifications
4.1 Colour-matching functions
The colour-matching functions xyλλ,,z λ of the CIE 1931 standard colorimetric observer are
() () ()
defined by the values given in Table 1, and those xyλλ,,z λ of the CIE 1964 standard
() () ()
10 10 10
colorimetric observer are defined by the values given in Table 2. The values are given at 1 nm wavelength
intervals from 360 nm to 830 nm. If values are required at closer wavelength intervals than 1 nm, they
should be derived by linear interpolation.
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4.2 Spectral chromaticity coordinates
Tables 1 and 2 also give values for the spectral chromaticity coordinates, x(λ), y(λ), z(λ); x (λ), y (λ),
10 10
z (λ); these have been derived from the appropriate colour-matching functions by forming the ratios
10
according to Formulae (1) to (6):
x λ
()
x ()λ = (1)
xyλλ+ +z λ
() () ()
y λ
()
y λ = (2)
()
xyλλ+ +z λ
() () ()
z λ
()
z λ = (3)
()
xyλλ+ +z λ
() () ()
and
x λ
()
10
x λ = (4)
()
10
xyλλ+ +z λ
() () ()
10 10 10
y λ
()
10
y λ = (5)
()
10
xyλλ+ +z λ
() () ()
10 10 10
z λ
()
10
z λ = (6)
()
10
xyλλ+ +z λ
() () ()
10 10 10
NOTE All wavelengths are for standard air.
5 Derivation of the colour-matching functions for the CIE 1931 standard
colorimetric observer
5.1 Experimental basis
The CIE 1931 colour-matching functions, xyλλ,,z λ , were derived from experimental work
() () ()
[1] [2]
carried out by Wright and Guild in which a total of 17 observers matched the monochromatic
stimuli of the spectrum, over the range of about 400 nm to 700 nm, with additive mixtures of red, green
and blue lights, using observing fields of 2° angular subtense.
5.2 Transformation procedures
The experimental results were converted into those that would have been obtained if the matching had
been carried out using, as reference colour stimuli, monochromatic radiations of wavelengths 700 nm
for the red [R], 546,1 nm for the green [G] and 435,8 nm for the blue [B], measured in units such that
equal quantities of [R], [G] and [B] were required to match the equi-energy spectrum.
The results for the 17 observers were averaged and then slightly adjusted so that by adding together
suitable proportions of the [R], [G], [B] colour-matching functions rgλλ,,b λ it was possible to
() () ()
obtain a function identical to that of the CIE spectral luminous efficiency, V(λ); the proportions used
were in the ratios of 1,000 0 to 4,590 7 to 0,060 1, and these were then the relative luminances of unit
quantities of [R], [G] and [B]. The CIE 1931 colour-matching functions were then determined by
Formulae (7) to (9):
 
xrλλ= 0,490+ ,,31gbλλ+ 020 n (7)
() () () ()
 
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 
yrλλ= 0,176 97 + 0,,812 40gbλλ+ 0 01063 n (8)
() () () ()
 
 
zrλλ= 0,000+ ,,01gbλλ+ 099 n (9)
() () () ()
 
where
n is a normalizing constant given by Formula (10).
V λ
()
n= (10)
0,176 97rgλλ+ 0,,812 40 + 0 01063b λ
() () ()
n is a constant, not a function of wavelength, because the coefficients 0,176 97, 0,812 40, and 0,010 63
are in the same ratios to one another as the ratio of 1,000 0 to 4,590 7 to 0,060 1; n is equal to For-
mula (11).
1,000 0 ++ 4,590 7 0,060 1
= 55,650 8 (11)
0,176 97 ++ 0,812 40 0,010 63
The values of xyλλ,,z λ given in Table 1 from 360 nm to 400 nm and from 700 nm to 830 nm are
() () ()
extrapolations.
5.3 Transformation properties
The transformation given in Formulae (7) to (9) was chosen to achieve the following objectives:
1. The y λ function is identical to the V(λ) function.
()
2. The values of xyλλ,,z λ are all positive for all wavelengths of the spectrum (unlike
() () ()
rgλλ,,b λ , one of which is negative at most wavelengths because of the need to desaturate
() () ()
spectral stimuli when matching them with red, green and blue reference stimuli).
3. The values of z λ are zero for wavelengths longer than 650 nm.
()
4. The values of x λ are nearly zero at wavelengths around 505 nm.
()
5. The values of x λ and y λ are small at the short-wavelength end of the spectrum.
() ()
6. The equi-energy spectrum is specified by equal amounts of X, Y and Z.
Because the y λ function is identical to the V(λ) function, the Y tristimulus value is proportional to
()
luminance.
5.4 Comparison with earlier data
The values of xyλλ,,z λ given in Table 1 for the spectral range of 380 nm to 780 nm at 5 nm
() () ()
intervals, when rounded to four decimal places, agree closely with those originally published in 1931.
There are only three minor differences: at λ = 775 nm the new value of x λ is 0,000 1 instead of 0,000 0;
()
at λ = 555 nm, y λ = 1,000 0 instead of 1,000 2 and at λ = 740 nm, y λ = 0,000 2 instead of 0,000 3.
() ()
These changes are considered insignificant in most colorimetric computations.
When the relative luminances of unit quantities of [R], [G] and [B] are deduced from the data of Table 1,
the values obtained are 1,000 0 to 4,588 8 to 0,060 3 instead of 1,000 0 to 4,590 7 to 0,060 1, the relative
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radiances being 71,893 8 to 1,374 7 to 1,000 0 instead of 72,096 2 to 1,379 1 to 1,000 0. These changes
are also considered insignificant in practice.
The values given in CIE 15 at 5 nm intervals agree exactly with those given in Table 1.
6 Derivation of the colour-matching functions for the CIE 1964 standard
colorimetric observer
6.1 Experimental basis
The CIE 1964 colour-matching functions xyλλ,,z λ were derived from experimental work
() () ()
10 10 10
[3] [4]
carried out by Stiles and Burch and by Speranskaya in which a total of 67 observers matched
monochromatic stimuli of the spectrum from approximately 390 nm to 830 nm with additive mixtures
of red, green, and blue lights, using observing fields of 10° angular subtense (but ignoring the central
4° or so).
6.2 Transformation procedures
The experimental results were converted into those that would have been obtained if the matching had
been carried out using, as reference colour stimuli, monochromatic radiations of wavenumbers
−1 −1 −1
15 500 cm for the red [R ], 19 000 cm for the green [G ] and 22 500 cm for the blue [B ],
10 10 10
corresponding approximately to wavelengths 645,2 nm, 526,3 nm and 444,4 nm, respectively. The
units used for the quantities of [R ], [G ] and [B ] were such that equal amounts were required to
10 10 10
match the equi-energy spectrum. A weighted average of the results for the 67 observers was used to
provide a set of colour-matching functions rgνν,,b ν . The CIE 1964 colour-matching
() () ()
10 10 10
functions were then derived using Formulae (12) to (14):
xrνν=0,,341080 +0 189145gbνν+0,387529 (12)
() () () ()
10 10 10 10
yrνν=0,,139058 +0 837460gbνν+0,073316 (13)
() () () ()
10 10 10 10
zrνν=0,,000000 +0 039553gbνν+2,026200 (14)
() () () ()
10 10 10 10
In Table 2, the CIE 1964 colour-matching functions xyλλ,,z λ are given on a wavelength
() () ()
10 10 10
basis and were obtained by interpolation from the frequency-based functions given in Formulae (12) to
(14). The values in the range of 360 nm to 390 nm are extrapolations.
6.3 Transformation properties
The transformation given in Formulae (12) to (14) was chosen to achieve a colorimetric system (X ,
10
Y , Z ) having a coordinate system broadly similar to that of the CIE 1931 (X, Y, Z) system. However, in
10 10
the 1964 system, the data were not constrained to fit the CIE V(λ) spectral luminous efficiency function,
and the Y tristimulus value is not proportional to luminance calculated using the V(λ) function.
10
6.4 Comparison with earlier data
The values given in CIE 15 at 5 nm intervals agree exactly with those given in Table 2.
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7 Practical application of colour-matching functions for CIE standard
colorimetric observers
7.1 Obtaining tristimulus values
The data given in Tables 1 and 2 provide the tristimulus values and chromaticity coordinates of all
monochromatic stimuli directly or by interpolation. For stimuli consisting of radiation of various
wavelengths, the tristimulus values X, Y, Z and X , Y , Z are calculated by integration over the
10 10 10
spectral range 360 nm to 830 nm using Formul
...