SIST EN ISO/CIE 11664-4:2019

Colorimetry - Part 4: CIE 1976 L*a*b* colour space (ISO/CIE 11664-4:2019)

This document specifies a method of calculating the coordinates of the CIE 1976 L*a*b* colour space,
including correlates of lightness, chroma and hue. It includes two methods for calculating Euclidean
distances in this space to represent the perceived magnitude of colour differences.
This document is applicable to tristimulus values calculated using colour-matching functions of the
CIE 1931 standard colorimetric system or the CIE 1964 standard colorimetric system. This document
can be used for the specification of colour stimuli perceived as belonging to a reflecting or transmitting
object, where a three-dimensional space more uniform than tristimulus space is required.
This document does not apply to colour stimuli perceived as belonging to an area that appears to be
emitting light as a primary light source, or that appears to be specularly reflecting such light.
This document is applicable to self-luminous displays, such as cathode ray tubes, if they are being used
to simulate reflecting or transmitting objects and if the stimuli are appropriately normalized.
Calculating the reverse transformation is shown in Annex A.

Farbmetrik - Teil 4: CIE 1976 L*a*b* Farbenraum (ISO/CIE 11664-4:2019)

Dieses Dokument legt das Verfahren zum Berechnen der Koordinaten des L*a*b*-Farbenraums CIE 1976 fest, Korrelate von Helligkeit, Buntheit und Buntton eingeschlossen. Sie legt zwei Verfahren zum Berechnen euklidischer Abstände in diesem Farbenraum fest, die der empfindungsgemäßen Größe der Farbabstände entsprechen.
Dieses Dokument gilt für Farbwerte, die nach den Spektralwertfunktionen des Normvalenzsystems CIE 1931 oder des Normvalenzsystems CIE 1964 berechnet sind. Dieses Dokument kann angewendet werden für die Festlegung von Farbreizen, die als zu einem reflektierenden oder transmittierenden Objekt zugehörig empfunden wurden, wenn ein dreidimensionaler Farbenraum, der gleichabständiger ist als der Farbenraum der Farbwerte, benötigt wird.
Dieses Dokument ist nicht anwendbar auf Farbreize, die als zu einer Fläche zugehörig empfunden wurden, die Licht als eine primäre Lichtquelle zu emittieren oder solches Licht gerichtet zu reflektieren scheint.
Dieses Dokument gilt auch für selbstleuchtende Displays, wie Kathodenstrahlröhren, wenn sie dazu verwendet werden, reflektierende oder transmittierende Objekte zu simulieren, und wenn die Farbreize in geeigneter Weise normiert sind.
Die Berechnung der Rücktransformation wird in Anhang A dargestellt.

Colorimétrie - Partie 4: Espace chromatique L*a*b* CIE 1976 (ISO 11664-4:2008)

Le présent document fixe une méthode de calcul des coordonnées de l'espace chromatique L*a*b* CIE 1976 ainsi que des correspondants de clarté, de chroma et de teinte. Il donne deux méthodes de calcul de la distance euclidienne dans cet espace, représentant la valeur perçue des différences de couleur.
Le présent document est applicable aux composantes trichromatiques calculées en utilisant les fonctions colorimétriques du système colorimétrique CIE 1931 normalisé ou du système colorimétrique CIE 1964 normalisé. Le présent document peut être utilisé pour la spécification de stimulus de couleur se rapportant à des objets qui réfléchissent ou qui transmettent la lumière, pour lesquels un espace chromatique tridimensionnel plus uniforme que le système trichromatique est nécessaire.
Le présent document ne s'applique pas à des stimulus de couleur se rapportant à des surfaces qui paraissent émettre de la lumière comme le font les sources primaires de lumière ou qui apparaissent réfléchir spéculairement de telles lumières.
Le présent document est applicable aux afficheurs auto-lumineux, tels que des tubes cathodiques, quand ils sont utilisés pour simuler des objets réfléchissants ou transparents, à condition que les stimulus soient convenablement normalisés.
Le calcul de la transformation inverse est présenté dans l'Annexe A.

Kolorimetrija - 4. del: Barvni prostor CIE 1976 L*a*b* (ISO/CIE 11664-4:2019)

Ta dokument določa metodo za izračun koordinat barvnega prostora CIE 1976 L*a*b*, vključno s korelacijo svetlobe, barv in odtenka. Vključuje dve metodi za izračun evklidskih razdalj v tem prostoru za označitev magnitude teh barvnih razlik.
Ta dokument se uporablja za tristimulusne vrednosti, izračunane z uporabo barvno skladnih funkcij kolorimetričnega sistema v skladu s standardom CIE 1931 ali kolorimetričnega sistema v skladu s standardom CIE 1964. Ta dokument se lahko uporablja za specifikacijo barvnih stimulov, dojetih kot refleksni ali oddajni predmeti, pri čemer se zahteva tridimenzionalni prostor, enotnejši od tristimulusnega prostora.
Ta dokument se ne uporablja za barvne dražljaje, zaznane, da pripadajo območju, za katerega je videti, da oddaja svetlobo kot primarni svetlobni vir, ali za katerega je videti, da sijajno odseva takšno svetlobo.
Ta dokument se uporablja za samosvetilne zaslone, kot so katodne cevi, če se uporabljajo za simulacijo predmeta, ki odbija ali oddaja svetlobo, in če so dražljaji ustrezno normalizirani. Izračun povratne pretvorbe je prikazan v dodatku A.

General Information

• Status: Published
• Public Enquiry End Date: 30-Apr-2019
• Publication Date: 18-Aug-2019
• ICS: 17.180.20 - Colours and measurement of light
• Technical Committee: IBLP - Paints and varnishes
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 24-Jul-2019
• Due Date: 28-Sep-2019
• Completion Date: 19-Aug-2019
• Ref Project: EN ISO/CIE 11664-4:2019 - Colorimetry - Part 4: CIE 1976 L*a*b* colour space (ISO/CIE 11664-4:2019)

Relations

• Replaces: SIST EN ISO 11664-4:2011 - Colorimetry - Part 4: CIE 1976 L*a*b* Colour space (ISO 11664-4:2008)
• Effective Date: 01-Sep-2019

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO/CIE 11664-4:2019
01-september-2019
Nadomešča:
SIST EN ISO 11664-4:2011
Kolorimetrija - 4. del: Barvni prostor CIE 1976 L*a*b* (ISO/CIE 11664-4:2019)
Colorimetry - Part 4: CIE 1976 L*a*b* colour space (ISO/CIE 11664-4:2019)
Farbmetrik - Teil 4: CIE 1976 L*a*b* Farbenraum (ISO/CIE 11664-4:2019)
Colorimétrie - Partie 4: Espace chromatique L*a*b* CIE 1976 (ISO 11664-4:2008)
Ta slovenski standard je istoveten z: EN ISO/CIE 11664-4:2019
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
SIST EN ISO/CIE 11664-4:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO/CIE 11664-4:2019

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SIST EN ISO/CIE 11664-4:2019


EN ISO/CIE 11664-4
EUROPEAN STANDARD

NORME EUROPÉENNE

July 2019
EUROPÄISCHE NORM
ICS 17.180.20 Supersedes EN ISO 11664-4:2011
English Version

Colorimetry - Part 4: CIE 1976 L*a*b* colour space
(ISO/CIE 11664-4:2019)
Colorimétrie - Partie 4: Espace chromatique L*a*b* CIE Farbmetrik - Teil 4: CIE 1976 L*a*b* Farbenraum
1976 (ISO/CIE 11664-4:2019) (ISO/CIE 11664-4:2019)
This European Standard was approved by CEN on 8 June 2019.

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, Turkey 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
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/CIE 11664-4:2019 E
worldwide for CEN national Members.

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SIST EN ISO/CIE 11664-4:2019
EN ISO/CIE 11664-4:2019 (E)
Contents Page
European foreword . 3

2

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SIST EN ISO/CIE 11664-4:2019
EN ISO/CIE 11664-4:2019 (E)
European foreword
This document (EN ISO/CIE 11664-4:2019) has been prepared by Technical Committee CEI
"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 January 2020, and conflicting national standards shall
be withdrawn at the latest by January 2020.
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 11664-4:2011.
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, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO/CIE 11664-4:2019 has been approved by CEN as EN ISO/CIE 11664-4:2019 without any
modification.


3

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SIST EN ISO/CIE 11664-4:2019

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SIST EN ISO/CIE 11664-4:2019
INTERNATIONAL ISO/CIE
STANDARD 11664-4
First edition
2019-06
Colorimetry —
Part 4:
CIE 1976 L*a*b* colour space
Colorimétrie —
Partie 4: Espace chromatique L*a*b* CIE 1976
Reference number
ISO/CIE 11664-4:2019(E)
©
ISO/CIE 2019

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SIST EN ISO/CIE 11664-4:2019
ISO/CIE 11664-4:2019(E)

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
CP 401 • Ch. de Blandonnet 8 Babenbergerstraße 9/9A
CH-1214 Vernier, Geneva A-1010 Vienna, Austria
Phone: [phone] Phone: [phone]
Fax: [phone] Fax: [phone]
Email: [e-mail] Email: [e-mail]
Website: www.iso.org Website: www.cie.co.at
Published in Switzerland
ii © ISO/CIE 2019 – All rights reserved

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SIST EN ISO/CIE 11664-4:2019
ISO/CIE 11664-4:2019(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Calculation method . 2
5.1 Basic coordinates . 2
5.2 Correlates of lightness, chroma and hue. 4
5.3 Colour differences . 4
Annex A (informative) Reverse transformation . 7
Bibliography . 8
© ISO/CIE 2019 – All rights reserved iii

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SIST EN ISO/CIE 11664-4:2019
ISO/CIE 11664-4:2019(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.
This first edition of ISO/CIE 11664-4 cancels and replaces ISO 11664-4:2008 | CIE 11664-4:2007, of
which it constitutes a minor revision. The document has been editorially revised as per current ISO
rules and the references have been updated.
A list of all parts in the ISO 11664 and ISO/CIE 11664 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO/CIE 2019 – All rights reserved

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SIST EN ISO/CIE 11664-4:2019
ISO/CIE 11664-4:2019(E)

Introduction
The three-dimensional colour space produced by plotting CIE tristimulus values (X, Y, Z) in rectangular
coordinates is not visually uniform, nor is the (x,y,Y) space nor the two-dimensional CIE (x,y)
chromaticity diagram. Equal distances in these spaces do not represent equally perceptible differences
between colour stimuli. For this reason, in 1976, the CIE introduced and recommended two new
spaces (known as CIELAB and CIELUV) whose coordinates are nonlinear functions of X, Y and Z. The
recommendation was put forward in an attempt to unify the then very diverse practice in uniform
[1][2]
colour spaces and associated colour-difference formulae . Both these more-nearly uniform colour
spaces have become well accepted and widely used. Numerical values representing approximately the
magnitude of colour differences can be described by simple Euclidean distances in the spaces or by
more sophisticated formulae that improve the correlation with the perceived size of differences.
The purpose of this document is to define procedures for calculating the coordinates of the
CIE 1976 L*a*b* (CIELAB) colour space and the Euclidean colour difference values based on these
coordinates. This document does not cover more sophisticated colour-difference formulae based on
[3] [4] [5]
CIELAB, such as the CMC formula , the CIE94 formula , the DIN99 formula , and the CIEDE2000
[6][7] [8]
formula , nor does it cover the alternative uniform colour space, CIELUV .
© ISO/CIE 2019 – All rights reserved v

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SIST EN ISO/CIE 11664-4:2019

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SIST EN ISO/CIE 11664-4:2019
INTERNATIONAL STANDARD ISO/CIE 11664-4:2019(E)
Colorimetry —
Part 4:
CIE 1976 L*a*b* colour space
1 Scope
This document specifies a method of calculating the coordinates of the CIE 1976 L*a*b* colour space,
including correlates of lightness, chroma and hue. It includes two methods for calculating Euclidean
distances in this space to represent the perceived magnitude of colour differences.
This document is applicable to tristimulus values calculated using colour-matching functions of the
CIE 1931 standard colorimetric system or the CIE 1964 standard colorimetric system. This document
can be used for the specification of colour stimuli perceived as belonging to a reflecting or transmitting
object, where a three-dimensional space more uniform than tristimulus space is required.
This document does not apply to colour stimuli perceived as belonging to an area that appears to be
emitting light as a primary light source, or that appears to be specularly reflecting such light.
This document is applicable to self-luminous displ
...

SLOVENSKI STANDARD
oSIST prEN ISO 11664-4:2019
01-april-2019
Kolorimetrija - 4. del: Barvni prostor CIE 1976 L*a*b* (ISO/CIE/FDIS 11664-4:2019)
Colorimetry - Part 4: CIE 1976 L*a*b* Colour space (ISO/CIE/FDIS 11664-4:2019)
Farbmetrik - Teil 4: CIE 1976 L*a*b* Farbenraum (ISO/CIE/FDIS 11664-4:2019)
Colorimétrie - Partie 4: Espace chromatique L*a*b* CIE 1976 (ISO/CIE/FDIS 11664-
4:2019)
Ta slovenski standard je istoveten z: prEN ISO 11664-4
ICS:
17.180.20 Barve in merjenje svetlobe Colours and measurement of
light
oSIST prEN ISO 11664-4:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 11664-4:2019

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oSIST prEN ISO 11664-4:2019
FINAL
INTERNATIONAL ISO/CIE
DRAFT
STANDARD FDIS
11664-4
CIE
Colorimetry —
Secretariat: ISO secretariat
Voting begins on:
Part 4:
2019-02-11
CIE 1976 L*a*b* colour space
Voting terminates on:
2019-05-06
Colorimétrie —
Partie 4: Espace chromatique L*a*b* CIE 1976
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 11664-4:2019(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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oSIST prEN ISO 11664-4:2019
ISO/CIE FDIS 11664-4:2019(E)

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
CP 401 • Ch. de Blandonnet 8 Babenbergerstraße 9/9A
CH-1214 Vernier, Geneva A-1010 Vienna, Austria
Phone: [phone] Phone: [phone]
Fax: [phone] Fax: [phone]
Email: [e-mail] Email: [e-mail]
Website: www.iso.org Website: www.cie.co.at
Published in Switzerland
ii © ISO/CIE 2019 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST prEN ISO 11664-4:2019
ISO/CIE FDIS 11664-4:2019(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Calculation method . 2
5.1 Basic coordinates . 2
5.2 Correlates of lightness, chroma and hue. 4
5.3 Colour differences . 4
Annex A (informative) Reverse transformation . 7
Bibliography . 8
© ISO/CIE 2019 – All rights reserved iii

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oSIST prEN ISO 11664-4:2019
ISO/CIE FDIS 11664-4:2019(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.
This first edition of ISO/CIE 11664-4 cancels and replaces ISO 11664-4:2008 | CIE 11664-4:2007, of
which it constitutes a minor revision. The document has been editorially revised as per current ISO
rules and the references have been updated.
A list of all parts in the ISO 11664 and 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

---------------------- Page: 6 ----------------------
oSIST prEN ISO 11664-4:2019
ISO/CIE FDIS 11664-4:2019(E)

Introduction
The three-dimensional colour space produced by plotting CIE tristimulus values (X, Y, Z) in rectangular
coordinates is not visually uniform, nor is the (x,y,Y) space nor the two-dimensional CIE (x,y)
chromaticity diagram. Equal distances in these spaces do not represent equally perceptible differences
between colour stimuli. For this reason, in 1976, the CIE introduced and recommended two new
spaces (known as CIELAB and CIELUV) whose coordinates are nonlinear functions of X, Y and Z. The
recommendation was put forward in an attempt to unify the then very diverse practice in uniform
[1][2]
colour spaces and associated colour-difference formulae . Both these more-nearly uniform colour
spaces have become well accepted and widely used. Numerical values representing approximately the
magnitude of colour differences can be described by simple Euclidean distances in the spaces or by
more sophisticated formulae that improve the correlation with the perceived size of differences.
The purpose of this document is to define procedures for calculating the coordinates of the
CIE 1976 L*a*b* (CIELAB) colour space and the Euclidean colour difference values based on these
coordinates. This document does not cover more sophisticated colour-difference formulae based on
[3] [4] [5]
CIELAB, such as the CMC formula , the CIE94 formula , the DIN99 formula , and the CIEDE2000
[6][7] [8]
formula , nor does it cover the alternative uniform colour space, CIELUV .
© ISO/CIE 2019 – All rights reserved v

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oSIST prEN ISO 11664-4:2019

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oSIST prEN ISO 11664-4:2019
FINAL DRAFT INTERNATIONAL STANDARD ISO/CIE FDIS 11664-4:2019(E)
Colorimetry —
Part 4:
CIE 1976 L*a*b* colour space
1 Scope
This document specifies a method of calculating the coordinates of the CIE 1976 L*a*b* colour space,
including correlates of lightness, chroma and hue. It includes two methods for calculating Euclidean
distances in this space to represent the perceived magnitude of colour differences.
This document is applicable to tristimulus values calculated using colour-matching functions of the
CIE 1931 standard colorimetric system or the CIE 1964 standard colorimetric system. This document
can be used for the specification of colour stimuli perceived as belonging to a reflecting or transmitting
object, where a three-dimensional space more uniform than tristimulus space is required.
This document does not apply to colour stimuli perceived as belonging to an area that appears to be
emitting light as a primary light source, or that appears to be specularly reflecting such light.
This document is applicable to self-luminous displays, such as cathode ray tubes, if they are being used
to simulate reflecting or transmitting objects and if the stimuli are appropriately normalized.
Calculating the reverse transformation is shown in Annex A.
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/CIE 11664-1:2018, Colorimetry Part 1 — CIE Standard Colorimetric Observers
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CIE S 017 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/
© ISO/CIE 2019 – All rights reserved 1

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oSIST prEN ISO 11664-4:2019
ISO/CIE FDIS 11664-4:2019(E)

4 Symbols and abbreviated terms
X, Y, Z tristimulus values of test stimulus calculated using the colour-matching functions of
the CIE 1931 standard colorimetric system (also known as the CIE 2° standard colori-
metric system)
X , Y , Z tristimulus values of a specific white colour stimulus calculated using the colour-matching
n n n
functions of the CIE 1931 standard c
...