Paper and board — Determination of colour by diffuse reflectance — Part 3: Indoor illumination conditions (D50/2°)

This document specifies a method for measuring the colour of paper and board by the diffuse reflectance method with the elimination of specular gloss. This document is primarily intended for measuring the colour of paper and board to be used in the graphic arts industry, where that industry specifies the measurement of colour under D50/2° conditions in accordance with ISO 13655. This method differs from ISO 13655, in that the UV content of the illumination is adjusted to a different level. The method can be used to determine the colour of papers or boards that contain fluorescent whitening agents, provided the UV content of the illumination on the test piece has been adjusted to conform to that in the CIE illuminant C, using a fluorescent reference standard that fulfils the requirements for international fluorescent reference standards of level 3 (IR3) as prescribed by ISO 2469 with an assigned ISO brightness value provided by an authorized laboratory, as described in ISO 2470‑1. This document is not applicable to coloured papers or boards that incorporate fluorescent dyes or pigments.

Papier et carton — Détermination de la couleur par réflectance diffuse — Partie 3: Conditions d'éclairage intérieur (D50/2°)

Le présent document spécifie une méthode pour mesurer la couleur du papier et du carton par la méthode de la réflectance diffuse avec élimination du brillant spéculaire. Le présent document a pour principal objectif de mesurer la couleur du papier et du carton à utiliser dans l’industrie des arts graphiques, lorsque cette industrie spécifie le mesurage de la couleur dans les conditions D50/2° selon l’ISO 13655. Cette méthode diffère de l’ISO 13655 en ce que la teneur en UV de l’éclairage est réglée à un niveau différent. La méthode peut être utilisée pour déterminer la couleur des papiers et cartons contenant des agents d’azurage fluorescents, sous réserve que la teneur en UV de l’éclairage sur l’éprouvette ait été ajustée de manière à être conforme à celle de l’illuminant CIE C, à l’aide d’un étalon de référence fluorescent satisfaisant aux exigences applicables aux étalons de référence fluorescents internationaux de niveau 3 (IR3), comme spécifié dans l’ISO 2469, présentant un degré de blancheur ISO dont la valeur a été attribuée par un laboratoire agréé, comme décrit dans l’ISO 2470-1. Le présent document n’est pas applicable aux papiers et cartons colorés qui contiennent des colorants ou des pigments fluorescents.

General Information

Status
Published
Publication Date
18-Jul-2022
Current Stage
6060 - International Standard published
Due Date
06-Jan-2023
Completion Date
19-Jul-2022
Ref Project

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NORME ISO
INTERNATIONALE 5631-3
Quatrième édition
2022-07
Papier et carton — Détermination de
la couleur par réflectance diffuse —
Partie 3:
Conditions d'éclairage intérieur
(D50/2°)
Paper and board — Determination of colour by diffuse reflectance —
Part 3: Indoor illumination conditions (D50/2°)
Numéro de référence
ISO 5631-3:2022(F)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 5631-3:2022(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2022

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---------------------- Page: 2 ----------------------
ISO 5631-3:2022(F)
Sommaire Page

Avant-propos .............................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ..................................................................................................................................................................................1

3 Termes et définitions ...................................................................................................................................................................................... 1

4 Principe.......................................................................................................................................................................................................................... 3

5 Appareillage .............................................................................................................................................................................................................. 3

6 Échantillonnage et conditionnement ............................................................................................................................................. 4

7 Préparation des éprouvettes .................................................................................................................................................................. 4

8 Mode opératoire ................................................................................................................................................................................................... 5

9 Calcul ................................................................................................................................................................................................................................ 5

9.1 Composantes trichromatiques CIE ....................................................................................................................................... 5

9.2 Coordonnées CIELAB ........................................................................................................................................................................ 5

9.3 Dispersion des résultats ................................................................................................................................................................ 6

10 Expression des résultats ............................................................................................................................................................................. 6

11 Fidélité ............................................................................................................................................................................................................................ 6

12 Rapport d’essai ...................................................................................................................................................................................................... 6

Annexe A (normative) Caractéristiques spectrales des réflectomètres pour déterminer

les composantes trichromatiques .....................................................................................................................................................8

Bibliographie ...........................................................................................................................................................................................................................14

iii
© ISO 2022 – Tous droits réservés
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ISO 5631-3:2022(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www.

iso.org/directives).

L’attention est attirée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de

brevets reçues par l’ISO (voir www.iso.org/brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, la signification des termes et expressions

spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion

de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles

techniques au commerce (OTC), voir le lien suivant: www.iso.org/iso/fr/avant-propos.html.

Le comité chargé de l’élaboration du présent document est l’ISO/TC 6, Papiers, cartons et pâtes.

Cette quatrième édition annule et remplace la troisième édition (ISO 5631-3:2015), dont elle constitue

une révision mineure. Les modifications sont les suivantes:

— mise à jour des références normatives et bibliographiques de la CIE et communes ISO/CIE selon les

versions actuelles.

Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent

document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes

se trouve à l’adresse www.iso.org/fr/members.html.
© ISO 2022 – Tous droits réservés
---------------------- Page: 4 ----------------------
ISO 5631-3:2022(F)
Introduction

La couleur d’un objet peut être caractérisée de manière unique au moyen d’un triplet de coordonnées

colorimétriques telles que les composantes trichromatiques CIE X, Y, Z ou les coordonnées L*, a*, b*

CIELAB 1976, pour un illuminant CIE et un observateur normalisé CIE spécifiés.

Outre les propriétés optiques de l’échantillon, les valeurs de ces coordonnées dépendent des conditions

de mesurage, notamment des caractéristiques spectrales et géométriques de l’appareil utilisé. Il

convient donc de lire le présent document conjointement avec l’ISO 2469.

Le présent document détaille le mesurage et la description de la couleur avec l’illuminant CIE D50

et l’observateur normalisé CIE 1931 (2°). Cette méthode s’applique en particulier à la comparaison

de papiers dans le domaine des arts graphiques, car ces conditions particulières d’illuminant et

d’observateur sont exigées par l’ISO 13655 dans ce secteur. Il faut toutefois souligner que ceci n’est

qu’une approche partielle du domaine des arts graphiques, car l’ISO 13655 spécifie également un

mesurage avec une géométrie 45:0 ou 0:45 d’une simple feuille sur un fond noir spécifié et exige

également que l’éclairage dans l’instrument soit ajusté aux conditions d’illuminant CIE D50.

Les autres parties de la présente Norme internationale décrivent les mesurages et les calculs

effectués de manière analogue en utilisant soit l’illuminant CIE C et l’observateur normalisé CIE 1931

(2°) (ISO 5631-1), soit l’illuminant normalisé CIE D65 et l’observateur normalisé CIE 1964 (10°)

(ISO 5631-2). Le choix des conditions relatives à l’illuminant est important lorsqu’il s’agit de déterminer

les coordonnées colorimétriques de papiers blancs contenant un agent d’azurage fluorescent. Dans

l’ISO 5631-2, la teneur en UV de l’éclairage est très supérieure, avoisinant les niveaux d’UV rencontrés

dans des conditions d’observation en extérieur.
© ISO 2022 – Tous droits réservés
---------------------- Page: 5 ----------------------
NORME INTERNATIONALE ISO 5631-3:2022(F)
Papier et carton — Détermination de la couleur par
réflectance diffuse —
Partie 3:
Conditions d'éclairage intérieur (D50/2°)
1 Domaine d’application

Le présent document spécifie une méthode pour mesurer la couleur du papier et du carton par la

méthode de la réflectance diffuse avec élimination du brillant spéculaire.

Le présent document a pour principal objectif de mesurer la couleur du papier et du carton à utiliser

dans l’industrie des arts graphiques, lorsque cette industrie spécifie le mesurage de la couleur dans les

conditions D50/2° selon l’ISO 13655. Cette méthode diffère de l’ISO 13655 en ce que la teneur en UV de

l’éclairage est réglée à un niveau différent.

La méthode peut être utilisée pour déterminer la couleur des papiers et cartons contenant des agents

d’azurage fluorescents, sous réserve que la teneur en UV de l’éclairage sur l’éprouvette ait été ajustée

de manière à être conforme à celle de l’illuminant CIE C, à l’aide d’un étalon de référence fluorescent

satisfaisant aux exigences applicables aux étalons de référence fluorescents internationaux de niveau 3

(IR3), comme spécifié dans l’ISO 2469, présentant un degré de blancheur ISO dont la valeur a été

attribuée par un laboratoire agréé, comme décrit dans l’ISO 2470-1.

Le présent document n’est pas applicable aux papiers et cartons colorés qui contiennent des colorants

ou des pigments fluorescents.
2 Références normatives

Les documents de référence suivants sont indispensables pour l’application du présent document. Pour

les références datées, seule l’édition citée s’applique. Pour les références non datées, la dernière édition

du document de référence s’applique (y compris les éventuels amendements).
ISO 186, Papier et carton — Échantillonnage pour déterminer la qualité moyenne

ISO 2469, Papier, carton et pâtes — Mesurage du facteur de luminance énergétique diffuse (facteur de

réflectance diffuse)

ISO 2470-1, Papier, carton et pâtes — Mesurage du facteur de réflectance diffuse dans le bleu — Partie 1:

Conditions d'éclairage intérieur de jour (degré de blancheur ISO)

ASTM E308, Standard Practice for Computing the Colors of Objects by Using the CIE System

CIE Publication 015:2018, Colorimetry, 4th ed
3 Termes et définitions

Pour les besoins du présent document, les termes et définitions suivants s’appliquent.

L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en

normalisation, consultables aux adresses suivantes:

— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp

— IEC Electropedia: disponible à l’adresse https:// www .electropedia .org/
© ISO 2022 – Tous droits réservés
---------------------- Page: 6 ----------------------
ISO 5631-3:2022(F)
3.1
facteur de luminance énergétique

rapport de la luminance énergétique d’un élément de surface d’un corps dans la direction délimitée par

un cône donné dont le sommet se trouve au niveau de l’élément de surface, à la luminance énergétique

du diffuseur parfait par réflexion, dans les mêmes conditions d’éclairage

Note 1 à l'article: Pour les matériaux fluorescents (luminescents), le facteur de luminance énergétique totale, β,

est la somme de deux grandeurs, le facteur de luminance énergétique par réflexion, β , et le facteur de luminance

énergétique par luminescence, β , de sorte que β = β + β .
L R L

Pour les matériaux non fluorescents, le facteur de luminance énergétique par réflexion, β , est numériquement

égal au facteur de réflectance, R.
3.2
facteur de luminance énergétique intrinsèque

facteur de luminance énergétique (3.1) d’une couche ou d’une liasse de matériau suffisamment épaisse

pour être opaque, de sorte que l’augmentation de l’épaisseur de la liasse par doublement du nombre de

feuilles la constituant n’engendre aucune modification du facteur de luminance énergétique mesuré

Note 1 à l'article: Le facteur de luminance énergétique intrinsèque est souvent exprimé sous forme de

pourcentage.
3.3
facteur de réflectance

rapport du rayonnement réfléchi par un élément de surface d’un corps dans la direction délimitée par

un cône donné dont le sommet se trouve au niveau de l’élément de surface, au rayonnement réfléchi par

le diffuseur parfait par réflexion, dans les mêmes conditions d’éclairage
Note 1 à l'article: Ce rapport est souvent exprimé sous forme de pourcentage.

Note 2 à l'article: Le fond a une incidence sur le facteur de réflectance si le corps est translucide.

3.4
facteur de réflectance intrinsèque

facteur de réflectance (3.3) d’une couche ou d’une liasse de matériau suffisamment épaisse pour être

opaque, de sorte que l’augmentation de l’épaisseur de la liasse par doublement du nombre de feuilles la

constituant n’engendre aucune modification du facteur de réflectance mesuré

Note 1 à l'article: Le facteur de réflectance d’une feuille non opaque dépend du fond et n’est pas une propriété du

matériau.
3.5
composantes trichromatiques
X, Y, Z

quantité des trois stimuli de couleur normalisés, dans un système chromatique donné, nécessaire pour

correspondre à la couleur du stimulus considéré

Note 1 à l'article: Dans le présent document, l’illuminant CIE D50 et l’observateur normalisé CIE 1931 (2°) sont

utilisés pour définir le système trichromatique.

Note 2 à l'article: Aucun indice n’est utilisé pour respecter la convention CIE selon laquelle les composantes

trichromatiques ne comportent pas d’indice lorsque l’on utilise l’observateur normalisé CIE 1931 (2°) [l’indice 10

est utilisé pour les composantes trichromatiques obtenues lorsque l’on utilise l’observateur normalisé CIE 1964

(10°)].
© ISO 2022 – Tous droits réservés
---------------------- Page: 7 ----------------------
ISO 5631-3:2022(F)
3.6
espace chromatique CIELAB

espace chromatique à trois dimensions approximativement uniforme, obtenu en portant en coordonnées

rectangulaires les grandeurs L*, a*, b* définies par les formules données dans l’Article 9

Note 1 à l'article: La grandeur L* est une mesure de la clarté de l’éprouvette, où L* = 0 correspond au noir et

L* = 100 est définie comme étant le diffuseur parfait par réflexion. Visuellement, les grandeurs a* et b*

représentent respectivement les axes rouge-vert et jaune-bleu de l’espace chromatique, de sorte que:

+a* est une mesure de la composante rouge de l’éprouvette;
−a* est une mesure de la composante verte de l’éprouvette;
+b* est une mesure de la composante jaune de l’éprouvette; et
−b* est une mesure de la composante bleue de l’éprouvette.
Si a* et b* sont toutes les deux égales à zéro, l’éprouvette est achromatique.
4 Principe

La lumière réfléchie par un échantillon dans des conditions d’éclairage UV spécifiées est analysée soit

au moyen d’un colorimètre à filtre trichromatique, soit à l’aide d’un spectrophotomètre continu, et les

coordonnées colorimétriques sont calculées pour les conditions D50/2°.
5 Appareillage

5.1 Réflectomètre, ayant les caractéristiques géométriques, spectrales et photométriques décrites

dans l’ISO 2469 et étalonné conformément aux dispositions de l’ISO 2469.

Si des matériaux contenant des agents d’azurage fluorescents doivent être mesurés, le réflectomètre

doit être équipé d’une source de rayonnement avec un contrôle adéquat de la teneur en UV, réglée à

un niveau correspondant à l’illuminant C au moyen d’un étalon de référence, comme décrit dans

l’ISO 2470-1.

5.1.2 En cas d’utilisation d’un réflectomètre à filtre, un ensemble de filtres qui donne, conjointement

aux caractéristiques optiques de l’appareil de base, des réponses globales équivalentes aux composantes

trichromatiques CIE X, Y et Z du système colorimétrique normalisé CIE 1931 de l’éprouvette évaluée

pour l’illuminant CIE D50.

Dans le cas d’un réflectomètre à filtre, le rayonnement tombant sur l’éprouvette doit avoir une teneur

en UV correspondant à celle de l’illuminant CIE C.

5.1.3 En cas d’utilisation d’un spectrophotomètre continu, l’appareil doit avoir une fonction

permettant de calculer les composantes trichromatiques CIE X, Y et Z du système colorimétrique

normalisé CIE 1931 de l’éprouvette évaluée pour l’illuminant CIE D50, en utilisant les fonctions

de pondération indiquées en Annexe A, les Tableaux A.1 et A.2 étant utilisés pour les appareils sans

correction de la bande passante et les Tableaux A.3 et A.4 pour les appareils avec correction de la bande

passante.

Dans le cas d’un spectrophotomètre continu, l’appareil doit être équipé d’un filtre réglable avec une

longueur d’onde de coupure de 395 nm ou d’un système équivalent; ce filtre doit être réglé ou le système

doit être étalonné à l’aide de l’étalon de référence fluorescent (5.2.2), de sorte que la teneur en UV du

rayonnement tombant sur l’échantillon corresponde à celle de l’illuminant CIE C.
© ISO 2022 – Tous droits réservés
---------------------- Page: 8 ----------------------
ISO 5631-3:2022(F)

5.2 Étalons de référence, pour l’étalonnage de l’appareil et des étalons de travail, utilisés de manière

suffisamment fréquente pour garantir un étalonnage et un réglage du rayo
...

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Paper and board — Determination of colour by diffuse reflectance — Part 3: Indoor

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illumination conditions (D50/2°)
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Papier et carton — Détermination de la couleur par réflectance diffuse — Partie 3:

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Conditions d'éclairage intérieur (D50/2°)
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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

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ISO/FDIS 5631-3:2021
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Contents Page

Foreword .......................................................................................................................................................................... 8

Introduction .................................................................................................................................................................... 8

1 Scope .................................................................................................................................................................... 1

2 Normative references .................................................................................................................................... 1

3 Terms and definitions ................................................................................................................................... 1

4 Principle ............................................................................................................................................................. 3

5 Apparatus ........................................................................................................................................................... 3

6 Sampling and conditioning .......................................................................................................................... 4

7 Preparation of test pieces ............................................................................................................................ 4

8 Procedure........................................................................................................................................................... 4

9 Calculation ......................................................................................................................................................... 5

9.1 CIE tristimulus values .................................................................................................................................... 5

9.2 CIELAB coordinates ........................................................................................................................................ 5

9.3 Dispersion of the results............................................................................................................................... 6

10 Expression of results ...................................................................................................................................... 6

11 Precision ............................................................................................................................................................. 6

12 Test report ......................................................................................................................................................... 6

Annex A (normative) Spectral characteristics of reflectometers for determining tristimulus

values ................................................................................................................................................................... 8

A.1 Filter reflectometers ...................................................................................................................................... 8

A.2 Abridged spectrophotometers ................................................................................................................... 8

A.2.1 General ................................................................................................................................................................ 8

A.2.2 Procedure for using data without bandpass correction ................................................................... 8

A.2.3 Procedure for using data with bandpass correction .......................................................................... 9

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Bibliography ................................................................................................................................................................. 14

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ISO/FDIS 5631-3:2021
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Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national Formatted: English (United States)

standards bodies (ISO member bodies). The work of preparing International Standards is normally

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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

Formatted: English (United States)
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 Formatted: English (United States)

different types of ISO documents should be noted. This document was drafted in accordance with the

Formatted: English (United States)

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives www.iso.org/directives).

Formatted: English (United States)
Formatted: English (United States)

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/patentswww.iso.org/patents). Formatted: English (United States)

Any trade name used in this document is information given for the convenience of users and does not

Formatted: English (United States)
constitute an endorsement.
Formatted: English (United States)

For an explanation onof 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 the following Formatted: English (United States)

URL: Foreword - Supplementary informationwww.iso.org/iso/foreword.html.
Formatted: English (United States)
Formatted: English (United States)
The committee responsible for this document ISO/TC 6, Paper, board and pulps.
Formatted: English (United States)

This fourth edition cancels and replaces the secondthird edition (ISO 5631-3:2015). A), of which it Formatted: English (United States)

constitutes a minor revision has been carried out to update the CIE, ISO and joint ISO/CIE references to

Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
their current versions.. The changes are as follows:
Formatted: English (United States)

ISO 5631 consists of the following parts, under the general title Paper and board — Determination of

Formatted: English (United States)
colour by diffuse reflectance:
— Part 1: Indoor daylight conditions (C/2°)
— Part 2: Outdoor daylight conditions (D65/10°)
— Part 3: Indoor illumination conditions (D50/2°)

— update of the CIE and joint ISO/CIE Normative and Bibliographic references to current

versions.

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.
Formatted: Justified
viii © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/FDIS 5631-3:2021
Formatted: Header, Adjust space between Latin and Asian
text, Adjust space between Asian text and numbers
Formatted: Font: Arial, English (United Kingdom)
Introduction

The colour of an object can be uniquely characterized by means of a triplet of colour coordinates such as

the CIE X,Y, Z tristimulus values or the CIELAB 1976 L*, a*, b* coordinates for a specified CIE illuminant

and CIE standard observer.

Apart from the optical properties of the sample, the values of such coordinates depend upon the

conditions of measurement, particularly the spectral and geometric characteristics of the instrument

used. This part of ISO 5631document should therefore be read in conjunction with ISO 2469.

This part of ISO 5631document describes the measurement and description of colour in terms of the

CIE illuminant D50 and the CIE 1931 (2°) standard observer. The method is especially applicable to the

comparison of papers in graphic arts situations since these particular illuminant/observer conditions

are required by ISO 13655 for the graphic arts industry. It is, however, emphasized that this is only a

partial approach to the graphic arts conditions, since ISO 13655 also specifies measurement with a 45:0

or 0:45 geometry of a single sheet over a specified black backing and also requires that the illumination

in the light booth be adjusted to CIE illuminant D50 conditions.

The other parts of this International Standard describe measurements and calculations carried out in an

analogous manner using either the CIE illuminant C and the CIE 1931 (2°) standard observer

(ISO 5631-1) or the CIE standard illuminant D65 and the CIE 1964 (10°) standard observer

(ISO 5631-2). The choice of illuminant conditions is important when determining the colour

coordinates of white papers containing a fluorescent whitening agent. In ISO 5631-2, the UV content of

the illumination is much higher, approximating UV levels encountered in outdoor viewing conditions

Formatted: Justified
© ISO 2021 – All rights reserved ix
---------------------- Page: 7 ----------------------
Formatted: German (Germany)
ISO/FDIS 5631-3:20212022(E)
FINAL DRAFT INTERNATIONAL STANDARD
Formatted: German (Germany)
Formatted: Font: Cambria
Paper and board — Determination of colour by diffuse
reflectance — Part 3: Indoor illumination conditions (D50/2°)
1 Scope

This part of ISO 5631document specifies a method for measuring the colour of paper and board by the

diffuse reflectance method with the elimination of specular gloss.

This part of ISO 5631document is primarily intended for measuring the colour of paper and board to be

used in the graphic arts industry, where that industry specifies the measurement of colour under

D50/2° conditions in accordance with ISO 13655. This method differs from ISO 13655, in that the UV

content of the illumination is adjusted to a different level.

The method can be used to determine the colour of papers or boards that contain fluorescent whitening

agents, provided the UV content of the illumination on the test piece has been adjusted to conform to

that in the CIE illuminant C, using a fluorescent reference standard that fulfils the requirements for

international fluorescent reference standards of level 3 (IR3) as prescribed by ISO 2469 with an

assigned ISO brightness value (C/2°) provided by an authorized laboratory, as described in ISO 2470-1.

This part of ISO 5631document is not applicable to coloured papers or boards that incorporate

fluorescent dyes or pigments.
2 Normative references

The following referenced documents are indispensable for the application 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.

ISO 186, Paper and board — Sampling to determine average quality Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

ISO 2469, Paper, board and pulps — Measurement of diffuse radiance factor (diffuse reflectance factor)

ISO 2470-1, Paper, board and pulps — Measurement of diffuse blue reflectance factor — Part 1: Indoor

daylight conditions (ISO brightness)

ASTM E308, Standard Practice for Computing the Colors of Objects by Using the CIE System

CIE Publication 015:2018, Colorimetry, 4th ed Formatted: bib_book
Formatted: bib_year
Formatted: bib_publisher
3 Terms and definitions
Formatted: bib_editionno

For the purposes of this document, the following terms and definitions apply. Formatted: Adjust space between Latin and Asian text,

Adjust space between Asian text and numbers

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
© ISO 20212022 – All rights reserved 1
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ISO/FDIS 5631-3:2021
Formatted: Font: Arial, English (United Kingdom)
Formatted: Header, Adjust space between Latin and Asian
text, Adjust space between Asian text and numbers
3.1
radiance factor

ratio of the radiance of a surface element of a body in the direction delimited by a given cone, with its

apex at the surface element, to that of the perfect reflecting diffuser under the same conditions of

illumination

Note 1 to entry: For fluorescent (luminescent) materials, the total radiance factor, β, is the sum of two portions,

Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9

the reflected radiance factor, βR, and the luminescent radiance factor, βL, so that β = βR + βL.

cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

For non-fluorescent materials, the reflected radiance factor, βR, is numerically equal to the reflectance factor, R. Formatted: Font: Italic

3.2
intrinsic radiance factor
Formatted: Font: Italic

radiance factor (3.1) of a layer or pad of material thick enough to be opaque, such that increasing the

thickness of the pad by doubling the number of sheets results in no change in the measured radiance

factor

Note 1 to entry: The intrinsic radiance factor is often expressed as a percentage. Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
3.3
reflectance factor

ratio of the radiation reflected by a surface element of a body in the direction delimited by a given cone,

with its apex at the surface element to that of the perfect reflecting diffuser under the same conditions

of illumination
Note 1 to entry: The ratio is often expressed as a percentage.
Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

Note 2 to entry: The reflectance factor is influenced by the backing if the body is translucent.

3.4
intrinsic reflectance factor

reflectance factor (3.3) of a layer or pad of material thick enough to be opaque, such that increasing the Formatted: Font: Italic

thickness of the pad by doubling the number of sheets results in no change in the measured reflectance

factor

Note 1 to entry: The reflectance factor of a non-opaque sheet is dependent on the background and is not a Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
material property.
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
3.5
tristimulus values
X, Y, Z

amount of the three reference colour stimuli, in a given chromatic system, required to match the

stimulus considered

Note 1 to entry: In this part of ISO 5631document, the CIE illuminant D50 and the CIE 1931 (2°) standard Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
observer are used to define the trichromatic system.
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

Note 2 to entry: No subscript is applied to conform to the CIE convention that tristimulus values have no

subscript when the CIE 1931 (2°) standard observer is used [the subscript 10 is applied for tristimulus values that

are obtained using the CIE 1964 (10°) standard observer].
3.6
2 © ISO 20212022– All rights reserved
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ISO/FDIS 5631-3:2021
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text, Adjust space between Asian text and numbers
Formatted: Font: Arial, English (United Kingdom)
CIELAB colour space

three-dimensional, approximately uniform colour space, produced by plotting, in rectangular

coordinates L*, a*, b*, quantities defined by the formulae given in Clause 9

Note 1 to entry: The quantity, L*, is a measure of the lightness of the test piece, where L* = 0 corresponds to

Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9

black and L* = 100 is defined by the perfect reflecting diffuser. Visually, the quantities a* and b* represent

cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
respectively the red-green and yellow-blue axes in colour space, such that
+a* is a measure of the degree of redness of the test piece,
−a* is a measure of the degree of greenness of the test piece,
+b* is a measure of the degree of yellowness of the test piece, and
−b* is a measure of the degree of blueness of the test piece.
If both a* and b* are equal to zero, the test piece is achromatic.
4 Principle

The light reflected from a sample under specified UV illumination conditions is analysed either by a

tristimulus-filter colorimeter or by an abridged spectrophotometer, and the colour coordinates are then

calculated for D50/2° conditions.
5 Apparatus

5.1 Reflectometer, having the geometric, spectral, and photometric characteristics described in Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
ISO 2469, and calibrated in accordance with the provisions of ISO 2469.
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

If materials containing fluorescent whitening agents are to be measured, the reflectometer shall be

equipped with a radiation source having an adequate UV-content control, adjusted to a UV condition

corresponding to the C illuminant by the use of a reference standard, as described in ISO 2470-1.

5.1.2 In the case of a filter reflectometer, a set of filters that, in conjunction with the optical Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9

characteristics of the basic instrument, give overall responses equivalent to the CIE tristimulus values X,

cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

Y, and Z of the CIE 1931 standard colorimetric system of the test piece evaluated for the CIE illuminant

D50.

In the case of a filter reflectometer, the radiation falling upon the test piece shall have a UV content

corresponding to that of the CIE illuminant C.
Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

5.1.3 In the case of an abridged spectrophotometer, the instrument shall have a function that permits

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9

calculation of the CIE tristimulus values X, Y, and Z of the CIE 1931 standard colorimetric system of the

cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

test piece evaluated for the CIE illuminant D50, using the weighting functions given in Annex A, where

Formatted: cite_app

the Tables A.1 and A.2 are used for instruments without bandpass correction and Tables A.3 and A.4

are used for instruments with bandpass correction.

In the case of an abridged spectrophotometer, the instrument shall have an adjustable filter with a cut-

off wavelength of 395 nm or some other equivalent system, and this filter shall be adjusted or the

system shall be calibrated with the help of the fluorescent reference standard (5.2.2), so that the UV

content of the illumination falling upon the sample corresponds to that of the CIE illuminant C.

5.2 Reference standards, for calibration of the instrument and the working standards, used frequently Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
enough to ensure satisfactory calibration and UV adjustment.
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
© ISO 20212022– All rights reserved 3
---------------------- Page: 10 ----------------------
ISO/FDIS 5631-3:2021
Formatted: Header, Adjust space between Latin and Asian
text, Adjust space between Asian text and numbers
Formatted: Font: Arial, English (United Kingdom)

5.2.1 Non-fluorescent reference standard, for photometric calibration, issued by an authorized

laboratory in accordance with the provisions of ISO 2469.

5.2.2 Fluorescent reference standard, for use in adjusting the UV content of the radiation incident

upon the sample, having an ISO brightness value assigned by an authorized laboratory, as prescribed in

ISO 2470-1.

5.3 Working standards, calibrated frequently enough to ensure that satisfactory calibration is

maintained.

5.3.1 Two plates of flat opal glass, ceramic, or other suitable material, cleaned and calibrated as

described in ISO 2469.

NOTE In some instruments, the function of the primary working standard can be taken over by a built-in

internal standard.

5.3.2 Stable plastic or other tablet, incorporating a fluorescent whitening agent.

5.4 Black cavity, having a reflectance factor which does not differ from its nominal value by more than

0,2 %, at all wavelengths. The black cavity should be stored upside down in a dust-free environment or

with a protective cover.

NOTE 1 The condition of the black cavity can be checked by reference to the instrument maker.

NOTE 2 The nominal value is given by the manufacturer.
6 Sampling and conditioning

If the tests are being made to evaluate a lot of paper or board, the sample shall be selected in

accordance with ISO 186. If the tests are made on another type of sample, make sure that the test pieces

taken are representative of the sample received.

Conditioning according to ISO 187 is recommended but not required, though preconditioning with

elevated temperatures should not be applied since it might change the optical properties.

7 Preparation of test pieces

Avoiding watermarks, dirt, and obvious defects, cut rectangular test pieces approximately

75 mm × 150 mm. Assemble at least 10 test pieces in a pad with their top sides uppermost; the number

should be such that doubling the number of test pieces does not alter the reflectance factor. Protect the

pad by placing an additional sheet of paper or board on both the top and bottom of the pad. Avoid

contamination and unnecessary exposure to light or heat.

Mark the top test piece in one corner to identify the sample and its top side, or to distinguish between

the two sides.

If the top side can be distinguished from the wire side, it shall be uppermost; if not, as can be the case

for papers manufactured on twin-wire machines, ensure that the same side of the sheet is uppermost.

8 Procedure

8.1 Ensure that calibration has been performed as described in ISO 2470-1 according to the instrument Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
maker's instructions.
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
4 © ISO 20212022– All rights reserved
---------------------- Page: 11 ----------------------
ISO/FDIS 5631-3:2021
Formatted: Header, Adjust space between Latin and Asian
text, Adjust space between Asian text and numbers
Formatted: Font: Arial, English (United Kingdom)

8.2 Remove the protective sheets from the top and the bottom of the test piece pad. Without touching

the test area, use the procedure appropriate to the instrument to obtain the three CIE tristimulus values

of the first test piece (or CIELAB values if the instrument is designed to report directly in this colour

space). Read and record the tristimulus values to the nearest 0,01 unit.

8.3 Move the uppermost test piece to the bottom of the pad and determine the values for subsequent

test pieces until at least 10 test pieces have been evaluated. If required, repeat the procedure for the

other side of the test pieces.
9 Calculation
9.1 CIE tristimulus values

If the instrument has a bandpass of 5 nm or narrower, calculate the CIE tristimulus values in accordance

with CIE Publication 015:2018, 4th ed. In all other cases, calculate the tristimulus values using the

appropriate weighting functions given in ASTM E308. If the instrument does not provide the CIE

tristimulus values directly, obtain them by calculation using the tables provided in Annex A.

9.2 CIELAB coordinates

Calculate the CIELAB coordinates from the tristimulus values X, Y, Z by means of the following

formulae:Formula (1):
1/3 Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1
L*=−116 Y Y 16 (1)
( )
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left
1/3 1/3
a*=−500 X X Y Y (2)
( ) ( )
1/3 1/3
b*=−200 Y Y Z Z (3)
( ) ( )

where X , Y , Z are the tristimulus values of the perfect reflecting diffuser under D50/2° conditions.

n n n
These are given as the “white point” values in Annex A.

Alternative equations shall, however, be used if any of the ratios X/X , Y/Y , Z/Z ≤ (24/116) are

n n n
satisfied as follows:
3 1/3 Formatted: Tab stops: 0.7 cm, Left + 1.4 cm, Left + 2.1

a) If (X/X ) ≤ (24/116) , replace the term (X/X ) in Formula (2) by the expression

n n
cm, Left + 2.8 cm, Left + 3.5 cm, Left + 4.2 cm, Left + 4.9

(841/108) (X/X ) + 16/116. cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

3 1/3

b) If (Y/Y ) ≤ (24/116) , replace the term (Y/Y ) in Formulae (1), (2) and (3) by the expression

n n
(841/108) (Y/Y ) + 16/116.
3 1/3

c) If (Z/Z ) ≤ (24/116) , replace the term (Z/Z ) in Formula (3) by the expression

n n
(84
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 5631-3
ISO/TC 6
Paper and board — Determination of
Secretariat: SCC
colour by diffuse reflectance —
Voting begins on:
2022-04-06
Part 3:
Voting terminates on:
Indoor illumination conditions
2022-06-01
(D50/2 degrees)
Papier et carton — Détermination de la couleur par réflectance
diffuse —
Partie 3: Conditions d'éclairage intérieur (D50/2 degrées)
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/FDIS 5631-3:2022(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 2022
---------------------- Page: 1 ----------------------
ISO/FDIS 5631-3:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 5631-3:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 3

5 Apparatus .................................................................................................................................................................................................................... 3

6 Sampling and conditioning ....................................................................................................................................................................... 4

7 Preparation of test pieces ..........................................................................................................................................................................4

8 Procedure ....................................................................................................................................................................................................................4

9 Calculation .................................................................................................................................................................................................................. 5

9.1 CIE tristimulus values ...................................................................................................................................................................... 5

9.2 CIELAB coordinates ........................................................................................................................................................................... 5

9.3 Dispersion of the results ................................................................................................................................................................ 5

10 Expression of results ....................................................................................................................................................................................... 6

11 Precision ....................................................................................................................................................................................................................... 6

12 Test report .................................................................................................................................................................................................................. 6

Annex A (normative) Spectral characteristics of reflectometers for determining tristimulus

values ............................................................................................................................................................................................................................... 7

Bibliography .............................................................................................................................................................................................................................12

iii
© ISO 2022 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/FDIS 5631-3:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see

www.iso.org/iso/foreword.html.
The committee responsible for this document ISO/TC 6, Paper, board and pulps.

This fourth edition cancels and replaces the third edition (ISO 5631-3:2015), of which it constitutes a

minor revision. The changes are as follows:

— update of the CIE and joint ISO/CIE Normative and Bibliographic references to current versions.

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.
© ISO 2022 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 5631-3:2022(E)
Introduction

The colour of an object can be uniquely characterized by means of a triplet of colour coordinates such as

the CIE X,Y, Z tristimulus values or the CIELAB 1976 L*, a*, b* coordinates for a specified CIE illuminant

and CIE standard observer.

Apart from the optical properties of the sample, the values of such coordinates depend upon the

conditions of measurement, particularly the spectral and geometric characteristics of the instrument

used. This document should therefore be read in conjunction with ISO 2469.

This document describes the measurement and description of colour in terms of the CIE illuminant

D50 and the CIE 1931 (2°) standard observer. The method is especially applicable to the comparison of

papers in graphic arts situations since these particular illuminant/observer conditions are required by

ISO 13655 for the graphic arts industry. It is, however, emphasized that this is only a partial approach to

the graphic arts conditions, since ISO 13655 also specifies measurement with a 45:0 or 0:45 geometry

of a single sheet over a specified black backing and also requires that the illumination in the light booth

be adjusted to CIE illuminant D50 conditions.

The other parts of this International Standard describe measurements and calculations carried out

in an analogous manner using either the CIE illuminant C and the CIE 1931 (2°) standard observer

(ISO 5631-1) or the CIE standard illuminant D65 and the CIE 1964 (10°) standard observer (ISO 5631-2).

The choice of illuminant conditions is important when determining the colour coordinates of white

papers containing a fluorescent whitening agent. In ISO 5631-2, the UV content of the illumination is

much higher, approximating UV levels encountered in outdoor viewing conditions
© ISO 2022 – All rights reserved
---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 5631-3:2022(E)
Paper and board — Determination of colour by diffuse
reflectance —
Part 3:
Indoor illumination conditions (D50/2 degrees)
1 Scope

This document specifies a method for measuring the colour of paper and board by the diffuse reflectance

method with the elimination of specular gloss.

This document is primarily intended for measuring the colour of paper and board to be used in

the graphic arts industry, where that industry specifies the measurement of colour under D50/2°

conditions in accordance with ISO 13655. This method differs from ISO 13655, in that the UV content of

the illumination is adjusted to a different level.

The method can be used to determine the colour of papers or boards that contain fluorescent whitening

agents, provided the UV content of the illumination on the test piece has been adjusted to conform

to that in the CIE illuminant C, using a fluorescent reference standard that fulfils the requirements

for international fluorescent reference standards of level 3 (IR3) as prescribed by ISO 2469 with an

assigned ISO brightness value (C/2°) provided by an authorized laboratory, as described in ISO 2470-1.

This document is not applicable to coloured papers or boards that incorporate fluorescent dyes or

pigments.
2 Normative references

The following referenced documents are indispensable for the application 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.
ISO 186, Paper and board — Sampling to determine average quality

ISO 2469, Paper, board and pulps — Measurement of diffuse radiance factor (diffuse reflectance factor)

ISO 2470-1, Paper, board and pulps — Measurement of diffuse blue reflectance factor — Part 1: Indoor

daylight conditions (ISO brightness)

ASTM E308, Standard Practice for Computing the Colors of Objects by Using the CIE System

CIE Publication 015:2018, Colorimetry, 4th ed
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminology databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
© ISO 2022 – All rights reserved
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ISO/FDIS 5631-3:2022(E)
3.1
radiance factor

ratio of the radiance of a surface element of a body in the direction delimited by a given cone, with

its apex at the surface element, to that of the perfect reflecting diffuser under the same conditions of

illumination

Note 1 to entry: For fluorescent (luminescent) materials, the total radiance factor, β, is the sum of two portions,

the reflected radiance factor, β , and the luminescent radiance factor, β , so that β = β + β .

R L R L

For non-fluorescent materials, the reflected radiance factor, β , is numerically equal to the reflectance factor, R.

3.2
intrinsic radiance factor

radiance factor (3.1) of a layer or pad of material thick enough to be opaque, such that increasing the

thickness of the pad by doubling the number of sheets results in no change in the measured radiance

factor

Note 1 to entry: The intrinsic radiance factor is often expressed as a percentage.

3.3
reflectance factor

ratio of the radiation reflected by a surface element of a body in the direction delimited by a given cone,

with its apex at the surface element to that of the perfect reflecting diffuser under the same conditions

of illumination
Note 1 to entry: The ratio is often expressed as a percentage.

Note 2 to entry: The reflectance factor is influenced by the backing if the body is translucent.

3.4
intrinsic reflectance factor

reflectance factor (3.3) of a layer or pad of material thick enough to be opaque, such that increasing the

thickness of the pad by doubling the number of sheets results in no change in the measured reflectance

factor

Note 1 to entry: The reflectance factor of a non-opaque sheet is dependent on the background and is not a

material property.
3.5
tristimulus values
X, Y, Z

amount of the three reference colour stimuli, in a given chromatic system, required to match the

stimulus considered

Note 1 to entry: In this document, the CIE illuminant D50 and the CIE 1931 (2°) standard observer are used to

define the trichromatic system.

Note 2 to entry: No subscript is applied to conform to the CIE convention that tristimulus values have no subscript

when the CIE 1931 (2°) standard observer is used [the subscript 10 is applied for tristimulus values that are

obtained using the CIE 1964 (10°) standard observer].
© ISO 2022 – All rights reserved
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ISO/FDIS 5631-3:2022(E)
3.6
CIELAB colour space

three-dimensional, approximately uniform colour space, produced by plotting, in rectangular

coordinates L*, a*, b*, quantities defined by the formulae given in Clause 9

Note 1 to entry: The quantity, L*, is a measure of the lightness of the test piece, where L* = 0 corresponds to black

and L* = 100 is defined by the perfect reflecting diffuser. Visually, the quantities a* and b* represent respectively

the red-green and yellow-blue axes in colour space, such that
+a* is a measure of the degree of redness of the test piece,
−a* is a measure of the degree of greenness of the test piece,
+b* is a measure of the degree of yellowness of the test piece, and
−b* is a measure of the degree of blueness of the test piece.
If both a* and b* are equal to zero, the test piece is achromatic.
4 Principle

The light reflected from a sample under specified UV illumination conditions is analysed either by a

tristimulus-filter colorimeter or by an abridged spectrophotometer, and the colour coordinates are

then calculated for D50/2° conditions.
5 Apparatus

5.1 Reflectometer, having the geometric, spectral, and photometric characteristics described in

ISO 2469, and calibrated in accordance with the provisions of ISO 2469.

If materials containing fluorescent whitening agents are to be measured, the reflectometer shall be

equipped with a radiation source having an adequate UV-content control, adjusted to a UV condition

corresponding to the C illuminant by the use of a reference standard, as described in ISO 2470-1.

5.1.2 In the case of a filter reflectometer, a set of filters that, in conjunction with the optical

characteristics of the basic instrument, give overall responses equivalent to the CIE tristimulus values

X, Y, and Z of the CIE 1931 standard colorimetric system of the test piece evaluated for the CIE illuminant

D50.

In the case of a filter reflectometer, the radiation falling upon the test piece shall have a UV content

corresponding to that of the CIE illuminant C.

5.1.3 In the case of an abridged spectrophotometer, the instrument shall have a function that permits

calculation of the CIE tristimulus values X, Y, and Z of the CIE 1931 standard colorimetric system of the

test piece evaluated for the CIE illuminant D50, using the weighting functions given in Annex A, where

the Tables A.1 and A.2 are used for instruments without bandpass correction and Tables A.3 and A.4

are
...

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