colorimetria iso 7724-1-1984

7/26/2019 Colorimetria ISO 7724-1-1984

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International Standard @ 7724/ 1

0

4

gb

,NTERNAT,ONAL ORGAN,ZAT,ON FOR STANDARDIZATION*MEX,WH APO,,HAfl OPrAHH3AL,MR flOCTAHflAPTH3AWl M*ORGANlSATlON INTERNATIONALE DE NORMALISATION

Paints and vainishes - Colorimetry -

Part 1: Principles

Peintures et vernis - Colorimdtrie - Partie I: Principes

First edition - 1984-10-01

UDC 667.6 : 636.66 Ref. No. IS0 7724/l-1984 (E)

Descriptors :

paints, varnishes, calorimetry.

3

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Foreword

IS0 (the International Organization for Standardization) is a worldwide federation of

national standards bodies (IS0 member bodies). The work of preparing International

Standards is normally carried out through IS0 technical committees. Every 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, govern-

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

Draft International Standards adopted by the technical committees are circulated to

the member bodies for approval before their acceptance as International Standards by

the IS0 Council. They are approved in accordance with IS0 procedures requiring at

least 75 approval by the member bodies voting.

International Standard IS0 7724/l was prepared by Technical Committee ISO/TC 35,

Paints and varnishes.

0 International Organization for Standardization, 1984 0

Printed in Switzerland

ii



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Contents

0 Introduction..

..............................................

1 Scope and field of application

.................................

2 References..

...............................................

3 Colour co-ordinates ................................. .........

3.1

Colour co-ordinates in the CIE 1964 supplementary standard

calorimetric system

.....................................

3.2

Colour co-ordinates in the CIE 1976 L*u* b*) colour space

...

Page

. . . . . .

1

. . . . . . 1

. . . . . . 1

. . . . . .

1

...... 1

...... 2

4 Standardilluminants................. ........... .......... ........... 4

5 Spectral radiometric characteristi cs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

5.1 General ...............................................

5.2

Illumination and viewing conditi ons.

.......................

......

4

...... 5

iii



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4/8

INTERNATIONAL STANDARD

IS0 7724/l-1984 (E)

Paints and varnishes - Colorimetry -

Part 1: Principles

0 Introduction

This International Standard, IS0 7724, comprises the following

parts :

Part I : Principles.

Part 2 : Colour measurement.

Part 3 : Calculation of colour differences.

Parts 1, 2 and 3 of IS0 7724 describe methods for the

instrumental determination of the colour co-ordinates and

colour differences of paint films, as required for such purposes

as

a) the objective description of colour differences between

a test specimen (a test panel coated with a paint, or a

specimen from a painted article) and a reference specimen;

b) determining colour deviations in the production of

painted articles so that the results may be used for the

control or regulation of the process;

c) the objective description of changes i n colour caused

by weathering and other chemical or physical influences;

d) the objective supervision of colour reference standards.

NOTE - Colour reference standards are subject to ageing, which may

lead in the course of time to pronounced changes i n colour. High ac-

curacy calorime try is required for the timely detection of these

changes. Th is is of particular importance when ordering aga inst such

reference standards.

1 Scope and field of application

This part of IS0 7724 describes the calorimetr ic terms and fun-

damental requirements necessary for determining the colour

co-ordinates of paint films and related materials.

2 References

IS0

2813, Paints and varnishes - Measurement of specular

gloss of non-metallic paint films at 2Q0, W and 85O.

IS0 3668, Paints and varnishes - Visual comparison of the

colour of paints.

IS0 i724/2, Paints and varnishes - Calorimetry - Part 2 :

Colour measurement.

IS0 772413, Paints and varnishes - Calorimetry - Part 3:

Calculation of colour differences.

CIE Publication No. 15, Calorimetry, Official CIE Recommenda-

tions.

CIE Publication No. 15, Supplement No. 2, Recommendations

on uniform color spaces - Color difference equations -

Psychometric color terms.

CIE Publication No. 38, Radiometric and photometric

characteristics of materials and their measurement.

3 Colour co-ordinates

A colour is uniquely characterized for a defined observer and a

defined light source by the co-ordinates of a point in a space

formed b y three mutually perpendicular vectors. From among

the various colour co-ordinates recommende d by the Commis -

sion lnternationale de Ilklairage (CIE), the colour co-ordinates

given in 3.1 and 3.2 are specified for calorimetr ic measureme nts

on paint films in accordance with this International Standard.

3.1 Colour co-ordinates in the CIE 1964

supplementary standard calorimetric system

The colour co-ordinates in this system (see CIE Publication

No. 15) are the tristimulus value Yt c and the chromatici ty co-

ordinates xl0 and ylo.

A=24

ylo = ho

c

p(A) j, ) AA

A = I

x10 =

x10

I YlO =

50

xl0 + vo + ZlO

x10 + YlO + Go



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5/8

IS0 7724/l-1984 (E)

The chromaticity co-ordinates are formed by the tristimulus

values

A= u

x10 = ho

c

qdA) X,,(A) AL,

=I

A=u

ZlO =

klo c 6pLU Zlo(L) AA and

A=I

yto

where

(p(l) denotes the colour stimulus function, which is the

product of the relative spectral power distr ibution SA for the

standard illuminant (see clause 4) and the spectral function

that characterizes the reflectance of the paint film (see

clause 5) ;

~tolo(l), y,,(L) and Go(A) are the colour-matching func-

tions (see note I) used to define the CIE 1964 standard col-

orimetric observer for observation fields of angular subtense

larger than 4O (loo observer) (see table I);

1 and u are the respective summation limits for the short-

wave and long-wave limits of the visible spectrum;

An

is the width of the wavelength interval (for the choice

of I and U, and

AA, see

IS0 772412);

klo is a normalizing factor calculated by using the equa-

tion

4, =

lcn/(~~sAi,o~~, *j

which causes the tristimulus value Ylofor the perfect reflec-

ting dif fuser to assume a value of 100.

In this system, the colour co-ordinates do not provide a percep-

tually uniform colour space (see 3.2).

NOTES

1 The coafficients ,W, j M and Mom ware formerly termed CIE

spectral tristimulus values or CIE trichromat ic weighting coaf-

ficiants.

2 Colour co-ordinates in the CIE 1931 standard colorimatric syste m

are defined by analogous equations using the colour-matching func-

tions Ffh 1, y(k) and fiA 1 of the CIE 1931 standard colorimat ric

observer for the 2O observation field. Colour-match ing functions at

5 nm wavelength intervals are given in CIE Publication No. 15.

The loo observation field corresponds more closely with practice than

the 2O observation field and is consistent with the viewing con-

ditions recommende d in IS0 3666 for the visual comparison of the

colour of paints.

3.2 Colour co-ordinates in the CIE 1976 (L*u*b*)

colour space

In comparison with the CIE 1964 calorimetri c system (see 3.11,

the colour co-ordinates in the perceptually more uniform

CIE 1976 U,a*b*) colour space (see CIE Publication No. 15

Supplement No. 2) are specified for the evaluation of colour

differences.

The colour co-ord inates are calculated from the following equa-

tions :

L* = 116(YlY,)3 - 16

for Y/Y, > 0608856

L+ = 903,3 ( Y/Y) for Y/Y, < 0608856

a = 500 yrX/X, - jl Y/Y)1

b* = 200 ff( Y/Y,,) - flz/z,)l

f(XlX, = (XIX,3

forX/X, > 0908856

fCXlX,l = 7,767 CXlX,) + 16/l 16 forX/X, < 0,008856

fCY/Y, = (Y/Y)3

for Y/Y, > 0908856

fC Y/Y,,) = 7,767 (Y/Y,,) + 16/116 for Y/Y, < 0,008856

fCZ/Z, = (Z/Z,)3

for Z/Z, > 0.008856

f(Z/Z,) = 7,787 (Z/Z,) + 16/116

forZ/Z, < 0.008856

X, Y, Z denote the loo tristimulus values of the paint film;

X,, Y,, Z, are the loo tristimulus values of the perfect

reflecting diffuser under the chosen standard illuminant (see

table 2).

NOTE - If 2O tristimulus values are used, L*, a,

b*

co-ordinates for

the 2O observer will be obtained. The corresponding values for X,, and

Z, can be calculated from the 2O chromati city co-ordinates for the

standard illumina nts D 65 and A (sea CIE Publication No. 151 with

Y = loo.

It is sometimes convenient to express colour not in terms of the

rectangular co-ordinates

L+,a*, b*,

but in terms of the

rectilinear lightness and the polar co-ordinates chroma and hue

(see CIE Publication No. 15 Supplement No. 2).

These may be calculated from

L*, a*, b

to give

CIE 1976 psychometric lightness

L*

CIE 1976 a

b

chroma qb= (a*2 + t)*2)1/2

CIE 1976 a

b

hue angle

h& = arctan

(b*la*)

between O and 360

2



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IS0 7724/l-1984 (E)

Table 1 - Colour-matching functions for the IO observer

at 5 nm wavelength intervals

1

nm

360

z

395

iii

410

415

420

425

iii

iii

z

ii

470

475

iii

iii

E

510

515

520

525

E

Ei

E

Es

670

575

Ei

590

595

J$#)

0,0002

0,0007

0,0024

0,0072

O,oooO

0.0001

8:E

0,0191

igz

0:1406

0,2045

O,W20

0,0045

EE

0:0214

0.2647

0,0295

0,3147

0,0387

0,3577

0,0496

0.3637

0,0621

0,3867

0,0747

0,3707

0.3430

0,3023

0,2541

0.1956

i%z

0:1282

0,1526

0,1652

0.1323

Ez

0:0162

0.0051

0,2199 1,0302

0,2536 0.7721

0,2977 0,5701

0,3391 0,4153

0.=

0.3024

0,0038

0,4608

0.0154

0.5314

0,0375

66067

0,0714

0,6857

0,1177

0.7618

0.1730

0,=

0.3042

0,3768

0,4516

Ei

0:7052

0,7936

0,6767

0,9918

0,9991

0,9973

0,9924

0,9556

0,9512

1,0142

1,0743

1,1185

1,1343

0.9152

iEi E

0:7774

0,7204

0.0007

0,0029

0.0105

0,0323

~~

EEi

0:9725

1,2625

Ez

1:9673

2;0273

I,9948

1,9007

1,7454

13549

1,3176

0,2185

0,1592

0,112O

0,=

0.0607

0.0431

0,0305

E%

o:w79

8:K

Ezi

0:OWO

x:Ei

Kz

0:WOO

L

nm

600

605

610

15

620

625

ii

E

E

El

670

675

iii

E

E

710

715

720

725

73035

74045

750

5;

765

770

z

qo(A)

11240

1.0991

1,-

,9507

0,8563

0,7549

0,6475

0,5351

O/l316

0.3437

0.2663,2043

0,1526.1122

0,0813

0,057s

0,0409.0266

0,0199,0138

Ei

0:0046

0,0031

0,0022

0.0015

0,OOlO,0007

O,ooo5.-

O.ooo3

0,0002

0,OOol

0.0001

0,OOol

;E

Yid4

Of6583

0,=

:%i

0:3961

~:~

:Ei

0:1402

0,1076.0812

0,0603.0441

0,0318

0,0226

0,0159.0111

O,W77,0054

0.0037,0026

0.0018

0,0012

O,ooo8

Ez

0:WO3

O,ooo2,OoOl

0,am

0,OoOl

O,oooO

::E

8:EE

q&i

O,oooO

O,oooO

xi

0:OOOO

O,oooO

O,oooO

EE

0:OOOO

O,oooO

~~

8:E

O,oooO

8:Ei

i:E

X:E

iEz

0:WOO

O,oooO

i:E

8:E

O,oooO

i%i

0:OWO

0.~

O,oooO

O.oooO

Table 2 - 10 tristimulus values for the perfect

reflecting diffuser for stardard illuminants D 55 and A

I

Tristimulus

I

Standard illuminant

value

D0S

1 A I

XII

94,81 111.14

Y"

lW,W

lW,W

&I

107,34 35,20

3



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7/8

IS0 7724/l-1984 (El

4 Standard illuminants specified for the calorimetric determination of a special

metamerism index (see clause 5 of IS0 7724/2).

The CIE standard illuminant D 65 which corresponds to natural

daylight at a correlated colour temperature of about 6 500 K

(see CIE Publication No. 15). should be specified for colour

measurements in accordance with this International Standard.

Numerical values for the relative spectral power distribution S,

of standard illuminants D 65 and A are given in table 3.

NOTE - Thestandard illuminant C corresoondstonaturaldavlightata

5 Spectral radiometric characteristics

-

correlated colourtemperature of6 744 K. Its spectral distribution does

not approach that of natural d aylight so closely as that of standard

illuminant D 65, especially in the ultraviolet region.

5.1 General

The standard illuminant A, which represents the light of a

tungsten lamp and corresponds in its spectral distr ibution to a

perfect black body at a temperature of 2 656 K, should be

Of the various possible spectral radiometric characteristics that

describe the reflecting properties of materials (see CIE Publica-

tion No. 361, the three characterist ics defined in 5.1 .l to 5.1.3

are used in this part of IS0 7724 for paint film calorimetry.

Table 3 - Relati ve spectral power distribution SAof standard

illuminants D 65 and A at 5 nm wavelength intervals

zi

410

415

420

425

ii

440

446

E

480

486

470

475

z

iii

E

510

515

520

525

630

535

E

550

555

E

570

575

580

585

E

sA,DlS

sA, A

WO

52,3

Fig

g.@J

10.90

1269

13,35

2:

91:5

92.5

93,4

14,71

16,15

1766

19,29

21,00

2;

95:8

104,9

110,9

22,79

24.67

2664

28.70

30.85

117.0

a~

117.4

35,41

117,8 37,81

116.3

w=

114.9

42,87

115.4

115,9

112,4

108,8

109,l

2%

51:cM

53,91

=m

109,4

108.6

107,8

106,3

104.8

2:

88:06

69,25

72,50

106.2

107.7

106,o

104,4

104,2

104,o

102.0

100.0

98.2

96,3

2:

92:2

75,79

79,13

82,52

86,95

89,41

92,91

=AJ

100,OO

10356

107,18

11060

11444

118.08

121,73

12539

1

nm

SA,s6

, A

FE

610

615

620

8W

893

:z

8717

129,04

132.70

136.35

13999

143,62

625

85,5

147.23

630

83,3

150.84

635

83,5

154,42

640

83,7

15798

645 81,9

161,52

656

655

Ei

670

80,O 16593

W1

168.51

802

171.96

81,2

17538

823

178.77

675

ii

E

80,3

182,12

78,3 18543

740 18670

69,7

191,93

70,7

195,12

700 71,6 198,26

705 73,0 201.36

710 74,3 204,41

715

68.0

207,41

720 61.6

210,36

725 65,7 213.27

730

a9

216,12

735 72,5

218.92

740

75,l

221.67

745

69,3

224.36

750

636

227,00

755

55,0

229.59

760

46,4

232.12

765

56.6

234.59

770

333

237,Ol

775

61

239,37

760

63.4

24166

L

4



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8/8

IS0 7724/l-1994 (E)

5.1 .l spectral reflectance factor R (1) : The ratio of the ra-

diant flux reflected in the directions within a given cone to that

reflected in the same directions by a perfect reflecting diffuser

identicall y irradiated in the observed waveleng th interval.

NOTE - In contrast to the recommendations of the CIE (see CIE

Publication No. 15), this part of IS0 7724 specifies the spectral refle c-

tance factor instead of the spectral radiance factor. The instruments

commerci ally available are not suitable for accurate mea surement of

the spectral radiance factor because of systemati c errors caused by the

divergence of the reflected light beams.

5.1.2 spectral reflectance

p(A): The ratio of the reflected ra-

diant flux to the incident flux in the observed wavelength

interval.

5.1.3 spectral diffuse reflectance e(d) (1) : The ratio of the

reflected radiant flux to the incident flux in the observed

wavelength interval measured with the specularl y reflected light

(gloss) excluded.

5.2

illumination and viewing conditions

The various modes for measuring the reflected radiation to be

specified for colour measure ments in accordance with this In-

ternational Standard are listed in table 4.

In the directional illuminatio n and viewing beams the angle bet-

ween the beam axi s and any ray shall not exceed 5O.

The diffuse illuminatio n and viewing takes place in an in-

tegrating sphere with an internal coating chosen su ch that the

light is diffused by the wall of the sphere uniformly and non-

selective ly with resp ect to wavelength. The total area of the

sample port of the integrating sphere shall not exceed 10 of

the total internal reflecting sphere area.

Specularl y reflected light can be partly suppressed for the il-

lumination and viewing conditions 8/d and d/8 by means of a

gloss trap. The results of the measureme nts are dependent on

the size, the position, and the structure of the gloss trap.

It has proved practical to use only gloss traps which exclude at

least 95 of the light reflected by a highly pol ished black glass

plate. The se traps should be tested using a primary standard

with a refractive index of between 150 and 155 as specified in

IS0 2913 for the measuremen t of specular gloss. The quotient

of the spectral reflectances of the higly polished black glass

plate measured with and without gloss trap shall fulfil the con-

dition

@(d)8/d(a)

@8ld(a)

< 0,05

for any wavelength.

Table 4 - Spectral radiometric characteristics for calorimetry of paint films

Spectral radiometric

characteristics

Symbol

Measurement conditions

Illumination Viewing

Designation

(Abbreviation)

Spectral

reflectance

factor

Spectral

reflectance

Spectral

diffuse

reflectance

&5/O(A)

R0/45(1)

Rd18(A)

Rtd) d/8(l)

@B/d(l)

e(d) B/d(l)

directional

450 iT 50

directional*

00 zk 100

diffuse,

integrating

sphere

diffuse,

integrating

sphere

with

gloss trap

directional**

8O zk 2O

directional

8O 1 2

directional

00 f 100

directional

450 + 50

directional**

8 +_ 2O

directional*

8= I 2O

diffuse,

integrating

sphere

diffuse,

integrating

sphere

with

gloss trap

45O/normal

(45/O)

normal/45O

(O/45)

diffuse/8O

(d/81

diffuse/8O

(d/8)

specular

reflection

excluded

8/diffuse

(8/d)

8Ofdiffuse

(8/d)

specular

reflection

excluded

*

The possibility of interreflections between a high gloss specimen and the illuminating optics should be

considered.

** This is contrary to the recommendations of the CIE (see CIE Publication No. 15) which permits the illumina-

tion or the viewing normal to the specimen (measurement conditions O/d and d/O). The illumination or observa-

tion angle with a small defined deviation from zero as specified in this part of IS0 7724 prevents interreflections

between the specimen and the illuminating or viewing optics when measuring high gloss specimens.

5


N f R l 04/26/2007 22 20 08 MDTd i ki i d i h li f IHS

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colorimetria iso 7724-1-1984

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