Paper and board — Determination of colour by diffuse reflectance — Part 2: Outdoor daylight conditions (D65/10°)

This document specifies a method for measuring the colour of paper and board by the diffuse reflectance method with the elimination of specular gloss. It 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 previously adjusted to give the calibrated colorimetric value corresponding to CIE standard illuminant D65, using a fluorescent reference standard with an assigned CIE whiteness (D65/10°) value provided by an authorized laboratory, as described in ISO 11475. 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 2: Conditions de lumière du jour extérieure (D65/10°)

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. Il peut être utilisé pour déterminer la couleur de papiers ou de cartons contenant des agents d’azurage fluorescents, à condition que la teneur en UV de l’éclairage sur l’éprouvette ait été ajustée au préalable pour fournir la valeur colorimétrique étalonnée correspondant à celle de l’illuminant normalisé CIE D65, à l’aide d’un étalon de référence fluorescent présentant un degré de blanc CIE (D65/10°) dont la valeur a été attribuée par un laboratoire agréé, comme décrit dans l’ISO 11475. 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
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INTERNATIONAL ISO
STANDARD 5631-2
Fourth edition
2022-07
Paper and board — Determination of
colour by diffuse reflectance —
Part 2:
Outdoor daylight conditions
(D65/10°)
Papier et carton — Détermination de la couleur par réflectance
diffuse —
Partie 2: Conditions de lumière du jour extérieure (D65/10°)
Reference number
ISO 5631-2:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 5631-2:2022(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 5631-2:2022(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 5631-2:2022(E)
Foreword

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

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

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

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

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

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

electrotechnical standardization.

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

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

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

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

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

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

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

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

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

constitute an endorsement.

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

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

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/

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

This fourth edition cancels and replaces the third edition (ISO 5631-2:2015), 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 5631-2:2022(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 standard

illuminant D65 and the CIE 1964 (10°) standard observer. The analogous measurement and description

of colour in terms of the CIE illuminant C and the CIE 1931 (2°) standard observer are described in

ISO 5631-1.

ISO 5631-3 describes the measurement and description of colour in terms of the CIE illuminant D50

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

in graphic arts situations where the customer wishes to make measurements under these illuminant/

observer conditions required by ISO 13655. The choice of illuminant conditions is important when

determining the colour coordinates of white papers containing a fluorescent whitening agent.

In ISO 5631-1, the UV content of the illumination is lower than those specified in this document,

approximating UV levels encountered in indoor rather than outdoor viewing conditions.

© ISO 2022 – All rights reserved
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 5631-2:2022(E)
Paper and board — Determination of colour by diffuse
reflectance —
Part 2:
Outdoor daylight conditions (D65/10°)
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.

It 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 previously adjusted to give

the calibrated colorimetric value corresponding to CIE standard illuminant D65, using a fluorescent

reference standard with an assigned CIE whiteness (D65/10°) value provided by an authorized

laboratory, as described in ISO 11475.

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

pigments.
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.

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 11475:2017, Paper and board — Determination of CIE whiteness, D65/10 degrees (outdoor daylight)

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
---------------------- Page: 6 ----------------------
ISO 5631-2:2022(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
10 10 10

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 standard illuminant D65 and the CIE 1964 (10°) standard observer are

used to define the trichromatic system.

Note 2 to entry: The subscript 10 is applied to conform to the CIE convention that tristimulus values have the

subscript 10 when the CIE 1964 (10°) standard observer is used.
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
© ISO 2022 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 5631-2:2022(E)
+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 conditions is analysed either by a tristimulus-filter

colorimeter or by an abridged spectrophotometer, and the colour coordinates are then calculated for

D65/10° 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 D65 standard illuminant by the use of a reference standard, as described in

ISO 11475.

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 1964 standard colorimetric system of the test piece evaluated for the CIE

10 10 10
standard illuminant D65.

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 standard illuminant D65.

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 1964 standard colorimetric system

10 10 10

of the test piece evaluated for the CIE standard illuminant D65, 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 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 standard illuminant D65.

5.2 Reference standards, for calibration of the instrument and the working standards, used

frequently enough to ensure satisfactory calibration and UV adjustment.

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 a CIE whiteness (D65/10°) value assigned by an authorized laboratory, as

prescribed in ISO 11475:2017, Annex B.
© ISO 2022 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 5631-2:2022(E)
5.3 Working standards, calibrated frequently enough to ensure tha
...

NORME ISO
INTERNATIONALE 5631-2
Quatrième édition
2022-07
Papier et carton — Détermination de
la couleur par réflectance diffuse —
Partie 2:
Conditions de lumière du jour
extérieure (D65/10°)
Paper and board — Determination of colour by diffuse reflectance —
Part 2: Outdoor daylight conditions (D65/10°)
Numéro de référence
ISO 5631-2:2022(F)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 5631-2:2022(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2022

Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette

publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,

y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut

être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.

ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: +41 22 749 01 11
E-mail: copyright@iso.org
Web: www.iso.org
Publié en Suisse
© ISO 2022 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO 5631-2:2022(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
---------------------- Page: 3 ----------------------
ISO 5631-2:2022(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 5631-2:2015), 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 5631-2:2022(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 normalisé

CIE D65 et l’observateur normalisé CIE 1964 (10°). Le mesurage et la description de couleur effectués

de manière analogue en utilisant l’illuminant CIE C et l’observateur normalisé CIE 1931 (2°) sont décrits

dans l’ISO 5631-1.

L’ISO 5631-3 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, dans les cas où le client souhaite effectuer des mesurages

dans les conditions d’illuminant/observateur exigées par l’ISO 13655. 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 5631-1, la teneur en UV de l’éclairage est

inférieure aux teneurs spécifiées dans le présent document, avoisinant les niveaux d’UV rencontrés dans

des conditions d’observation en intérieur, plutôt que dans des conditions d’observation en extérieur.

© ISO 2022 – Tous droits réservés
---------------------- Page: 5 ----------------------
NORME INTERNATIONALE ISO 5631-2:2022(F)
Papier et carton — Détermination de la couleur par
réflectance diffuse —
Partie 2:
Conditions de lumière du jour extérieure (D65/10°)
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.

Il peut être utilisé pour déterminer la couleur de papiers ou de cartons contenant des agents d’azurage

fluorescents, à condition que la teneur en UV de l’éclairage sur l’éprouvette ait été ajustée au préalable

pour fournir la valeur colorimétrique étalonnée correspondant à celle de l’illuminant normalisé

CIE D65, à l’aide d’un étalon de référence fluorescent présentant un degré de blanc CIE (D65/10°) dont

la valeur a été attribuée par un laboratoire agréé, comme décrit dans l’ISO 11475.

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 suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur

contenu, des exigences 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 11475:2017, Papier et carton — Détermination du degré de blanc CIE, D65/10 degrés (lumière du jour

extérieure)

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 5631-2:2022(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
10 10 10

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 normalisé CIE D65 et l’observateur normalisé

CIE 1964 (10°) sont utilisés pour définir le système trichromatique.

Note 2 à l'article: L’indice 10 est utilisé pour respecter la convention CIE selon laquelle les composantes

trichromatiques sont accompagnées de l’indice 10 lorsque l’on utilise l’observateur normalisé CIE 1964 (10°).

© ISO 2022 – Tous droits réservés
---------------------- Page: 7 ----------------------
ISO 5631-2:2022(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 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 D65/10°.
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 normalisé D65 au moyen d’un étalon de référence, comme décrit

dans l’ISO 11475.

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 1964 de l’éprouvette

10 10 10
évaluée pour l’illuminant normalisé CIE D65.

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 normalisé CIE D65.

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

10 10 10

normalisé CIE 1964 de l’éprouvette évaluée pour l’illuminant normalisé CIE D65, 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 normalisé CIE D65.

© ISO 2022 – Tous droits réservés
---------------------- Page: 8 ----------------------
ISO 5631-2:2022(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 rayonnement UV satisfaisants.

5.2.1 Étalon de référence non fluorescent, pour l’étalonnage photométrique, provenant d’un

laboratoire agréé conformément aux dispositions de l’ISO 2469.

5.2.2 Étalon de référence fluorescent, destiné au réglage de la teneur en UV du rayonnement

incident tombant sur l’échantillon, présentant un degré de blanc CIE (D65/10°) dont la valeur a été

attribuée par un laboratoire agréé, comme spécifié dans l’Annexe B de l’ISO 11475:2017.

5.3 Étalons de travail, étalonnés de manière suffisamment fréquente pour garantir le maintien d’un

étalonnage satisfaisant.

5.3.1 Deux plaques de verre opale, en céramique ou tout autre matériau adapté, nettoyées et

étalonnées comme décrit dans l’ISO 2469.

NOTE Dans certains appareils, la fonction de l’étalon de travail primaire peut être assurée par un étalon

interne intégré.

5.3.2 Plaque en plastique ou autre matériau stable, contenant un agent d’azurage f

...

ISO/WD nnn-n
Style Definition: RefNorm
ISO/TC 6
Style Definition: List Continue 1
2021-09-28
Style Definition: List Continue 5: Font: Indent: Hanging:
0.71 cm, Don't add space between paragraphs of the same
style
ISO/FDIS 5631-2:2022(E)
Style Definition: Body Text_Center
Committee identification: ISO/TC 6/WG 3
Style Definition: Dimension_100
Style Definition: Figure subtitle
Secretariat: SCC
Style Definition: Figure Graphic
Style Definition: bib_comment: Font: Cambria

Paper and board — Determination of colour by diffuse reflectance — Part 2: Outdoor

Style Definition: bib_deg: Font: Cambria
daylight conditions (D65/10°)
Style Definition: bib_suffix: Font: Cambria

Papier et carton — Détermination de la couleur par réflectance diffuse — Partie 2:

Style Definition: bib_unpubl: Font: Cambria
Conditions de lumière du jour extérieure (D65/10°)
Style Definition: cite_box: Font: Cambria
Style Definition: bib_medline: Font: Cambria
Style Definition: Base_Text: 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
Style Definition: Code: Tab stops: 0.57 cm, Left + 1.15 cm,
Left + 1.72 cm, Left + 2.3 cm, Left + 2.87 cm, Left + 3.45
cm, Left + 4.02 cm, Left + 4.6 cm, Left + 5.17 cm, Left +
5.74 cm, Left
Style Definition: List Continue 2 (-): Indent: Left: 0.69 cm,
Hanging: 1.43 cm, Space After: 12 pt
Style Definition: List Number 1: Tab stops: Not at 0.71 cm
Formatted: French (Switzerland)
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ISO/FDIS 5631-2:20212022(E)
Formatted: Section start: New page
© 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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 20212022 – All rights reserved iii
---------------------- Page: 2 ----------------------
ISO/FDIS/ 5631-2:20212022(E) Formatted: Left
Contents Page

Foreword .......................................................................................................................................................................... 5

Introduction .................................................................................................................................................................... 5

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

A.1 Filter reflectometers ...................................................................................................................................... 7

A.2 Abridged spectrophotometers ................................................................................................................... 7

A.2.1 General ................................................................................................................................................................ 7

A.2.2 Procedure for using data without bandpass correction ................................................................... 7

A.2.3 Procedure for using data with bandpass correction .......................................................................... 8

Bibliography ................................................................................................................................................................. 13

iv © ISO 20212022 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/FDIS 5631-2:20212022(E)
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

Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers

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. Formatted: English (United States)

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

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

constitute an endorsement. Formatted: English (United States)

For an explanation onof the voluntary nature of standards, the meaning of ISO specific terms and Formatted: English (United States)

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 third edition (ISO 5631-2:2015). A minor revision has been Formatted: English (United States)

carried out to update the Normative and Bibliographic CIE, ISO and joint ISO/CIE references to current

Formatted: Adjust space between Latin and Asian text,

versions.), of which it constitutes a minor revision. The changes are as follows: Adjust space between Asian text and numbers

Formatted: English (United States)

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

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.
© ISO 20212022 – All rights reserved v
---------------------- Page: 4 ----------------------
ISO/FDIS/ 5631-2:20212022(E) Formatted: Left
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 standard illuminant D65 and the CIE 1964 (10°) standard observer. The analogous measurement

and description of colour in terms of the CIE illuminant C and the CIE 1931 (2°) standard observer are

described in ISO 5631-1.

ISO 5631-3 describes the measurement and description of colour in terms of the CIE illuminant D50 and

the CIE 1931 (2°) standard observer. This method is especially applicable to comparison of papers in

graphic arts situations where the customer wishes to make measurements under these

illuminant/observer conditions required by ISO 13655. The choice of illuminant conditions is important

when determining the colour coordinates of white papers containing a fluorescent whitening agent. In

ISO 5631-1, the UV content of the illumination is lower than those specified in this part of

ISO 5631document, approximating UV levels encountered in indoor rather than outdoor viewing

conditions.
vi © ISO 20212022 – All rights reserved
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FINAL DRAFT INTERNATIONAL STANDARD Formatted: Font: Cambria
ISO /FDIS 5631-2:20212022(E)
Formatted Table
Formatted: Font: Cambria
Paper and board — Determination of colour by diffuse
reflectance — Part 2: Outdoor daylight conditions (D65/10°)
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.

It 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 previously adjusted to give the

calibrated colorimetric value corresponding to CIE standard illuminant D65, using a fluorescent

reference standard with an assigned CIE whiteness (D65/10°) value provided by an authorized

laboratory, as described in ISO 11475.

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

fluorescent dyes or pigments.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. 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 11475:2017, Paper and board — Determination of CIE whiteness, D65/10° degrees (outdoor

daylight)

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/
3.1
radiance factor
© ISO 20212022– All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/FDIS/ 5631-2:20212022(E) Formatted: Left

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

R L R L
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

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

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 Formatted: Font: Italic

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 Formatted: Font: Not Italic
10 10 10

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

Formatted: Font: Not Italic
stimulus considered
Formatted: Font: Not Italic

Note 1 to entry: In this part of ISO 5631document, the CIE standard illuminant D65 and the CIE 1964 (10°)

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
standard 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: The subscript 10 is applied to conform to the CIE convention that tristimulus values have the

subscript 10 when the CIE 1964 (10°) standard observer is used.
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
2 © ISO 20212022 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/FDIS 5631-2:20212022(E)

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 conditions is analysed either by a tristimulus-filter

colorimeter or by an abridged spectrophotometer, and the colour coordinates are then calculated for

D65/10° 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 D65 standard illuminant by the use of a reference standard, as described in

ISO 11475.

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

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

X10, Y10, and Z10 of the CIE 1964 standard colorimetric system of the test piece evaluated for the CIE

standard illuminant D65.

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 standard illuminant D65.

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

calculation of the CIE tristimulus values X , Y , and Z , of the CIE 1964 standard colorimetric system of

10 10 10
cm, Left + 5.6 cm, Left + 6.3 cm, Left + 7 cm, Left

the test piece evaluated for the CIE standard illuminant D65, 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 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 standard

illuminant D65.

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, L
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 5631-2
ISO/TC 6
Paper and board — Determination of
Secretariat: SCC
colour by diffuse reflectance —
Voting begins on:
2022-04-06
Part 2:
Voting terminates on:
Outdoor daylight conditions (D65/10
2022-06-01
degrees)
Papier et carton — Détermination de la couleur par réflectance
diffuse —
Partie 2: Conditions de lumière du jour extérieure (D65/10 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 5631-2:2022(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 5631-2:2022(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 5631-2:2022(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
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ISO/FDIS 5631-2:2022(E)
Foreword

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

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

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

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

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

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

electrotechnical standardization.

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

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

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

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

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

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

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

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

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

constitute an endorsement.

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

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

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

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

This fourth edition cancels and replaces the third edition (ISO 5631-2:2015), 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.
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ISO/FDIS 5631-2:2022(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 standard

illuminant D65 and the CIE 1964 (10°) standard observer. The analogous measurement and description

of colour in terms of the CIE illuminant C and the CIE 1931 (2°) standard observer are described in

ISO 5631-1.

ISO 5631-3 describes the measurement and description of colour in terms of the CIE illuminant D50

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

in graphic arts situations where the customer wishes to make measurements under these illuminant/

observer conditions required by ISO 13655. The choice of illuminant conditions is important when

determining the colour coordinates of white papers containing a fluorescent whitening agent.

In ISO 5631-1, the UV content of the illumination is lower than those specified in this document,

approximating UV levels encountered in indoor rather than outdoor viewing conditions.

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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 5631-2:2022(E)
Paper and board — Determination of colour by diffuse
reflectance —
Part 2:
Outdoor daylight conditions (D65/10 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.

It 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 previously adjusted to give

the calibrated colorimetric value corresponding to CIE standard illuminant D65, using a fluorescent

reference standard with an assigned CIE whiteness (D65/10°) value provided by an authorized

laboratory, as described in ISO 11475.

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

pigments.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. 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 11475:2017, Paper and board — Determination of CIE whiteness, D65/10 degrees (outdoor daylight)

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/
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ISO/FDIS 5631-2:2022(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
10 10 10

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 standard illuminant D65 and the CIE 1964 (10°) standard observer are

used to define the trichromatic system.

Note 2 to entry: The subscript 10 is applied to conform to the CIE convention that tristimulus values have the

subscript 10 when the CIE 1964 (10°) standard observer is used.
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
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ISO/FDIS 5631-2:2022(E)
+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 conditions is analysed either by a tristimulus-filter

colorimeter or by an abridged spectrophotometer, and the colour coordinates are then calculated for

D65/10° 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 D65 standard illuminant by the use of a reference standard, as described in

ISO 11475.

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 1964 standard colorimetric system of the test piece evaluated for the CIE

10 10 10
standard illuminant D65.

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 standard illuminant D65.

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 1964 standard colorimetric system

10 10 10

of the test piece evaluated for the CIE standard illuminant D65, 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 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 standard illuminant D65.

5.2 Reference standards, for calibration of the instrument and the working standards, used

frequently enough to ensure satisfactory calibration and UV adjustment.

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, havin
...

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