ISO 5631-2:2022
(Main)Paper and board — Determination of colour by diffuse reflectance — Part 2: Outdoor daylight conditions (D65/10°)
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.
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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
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ISO 5631-2:2022(E)
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
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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
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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.
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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.
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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/
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ISO 5631-2:2022(E)
3.1
radiance factor
β
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.
R
3.2
intrinsic radiance factor
β
∞
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
R
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
R
∞
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 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.
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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
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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,
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Publié en Suisse
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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
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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.
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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.
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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/
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ISO 5631-2:2022(F)
3.1
facteur de luminance énergétique
β
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
R
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
R
égal au facteur de réflectance, R.
3.2
facteur de luminance énergétique intrinsèque
β
∞
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
R
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
R
∞
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°).
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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.
3
© 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)
Formatted: French (Switzerland)
Formatted: English (United States)
Formatted: English (United States)
Formatted: French (Switzerland)
ii
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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
---------------------- Page: 5 ----------------------
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
β
© 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
R
3.2
intrinsic radiance factor
β∞
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
R
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
R
∞
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
ii
© 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
© ISO 2022 – All rights reserved
---------------------- Page: 3 ----------------------
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.
iv
© ISO 2022 – All rights reserved
---------------------- Page: 4 ----------------------
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
β
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.
R
3.2
intrinsic radiance factor
β
∞
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
R
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
R
∞
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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