Colorimetria ISO 7724-1-1984
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Transcript of 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
I=
s
Price based on 5 pages
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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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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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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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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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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
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