Sophie Jost, Coralie Cauwerts, and Pascale Avouac, "CIE 2017 color fidelity index Rf: a better index to predict perceived color difference?," J. Opt. Soc. Am. A 35, B202-B213 (2018)
The CIE General Color Rendering Index Ra is currently widely and
internationally used to assess the ability of white light sources to
render colors. But over the past decades, there has been increasing
evidence of its limitations. As a result of several years of
scientific work, the Commission Internationale de l’Eclairage (CIE)
published in April 2017 an updated calculation method. To reduce
misinterpretation by users and make a clear distinction with the other
aspects of color quality, the color rendering index was renamed color
fidelity index (CIE-Rf). Before proposing this index as a new
international standard for color fidelity prediction, there is a need
for validation. This paper presents a psychophysical experiment
designed to address this aim. Twelve observers evaluated color
differences of 16 color samples under eight pairs of light sources.
3000K and 4000K light-emitting diodes and fluorescent sources with
CIE-Rf values ranging from 64 to 94 were investigated. Results show
that the prediction of color differences is significantly better in
CAM02-UCS color space than in CIE or CIELAB, whatever the color matching functions. A
high correlation was found between perceived color differences and
CIE-Rf. This psychophysical experiment did not make it possible to
detect significant differences with the other tested color fidelity
indices (CIE-Ra, CQS-Qf, CRI2012, CRI-CAM02UCS, and IES-Rf). However,
there are some signs of an improvement of the prediction by CIE-Rf in
comparison to CIE-Ra. To increase, in further works, the chance to
detect potential significant differences between color fidelity
indices, some modifications of the experimental protocols are
suggested.
Perceived color difference collected using a James Heal scale.
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Figure files are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Article tables are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
P, Planckian radiator; D, Daylight illuminant; RMS, root
mean square; comb., combination.
Complementary color samples (not used in the calculation of
the general color rendering index).
Specifically selected to have high spatial and spectral
uniformities.
Table 2.
Characteristics of the 3000K Lamp Group
3000_Ref
3000_Fluo
3000_LED1
3000_LED2
3000_LED3
Booth
central
right
left
left
left
CCT (K)
2873
2954
2634
2632
2712
Duv
−0.003
−0.001
−0.009
−0.009
−0.006
0.4410
0.4390
0.4505
0.4506
0.4495
0.3968
0.4028
0.3860
0.3858
0.3934
Illuminance (lux)
254
260
254
254
257
Luminance ()
79
80
78
79
79
CIE-Rf
89
79
64
71
80
Table 3.
Characteristics of the 4000K Lamp Group
4000_Ref
4000_Fluo
4000_LED1
4000_LED2
4000_LED3
Booth
central
right
left
left
left
CCT (K)
3936
3891
3685
3786
4029
Duv
0.002
0.003
−0.003
0.000
0.004
0.3850
0.3879
0.3924
0.3900
0.3823
0.3843
0.3881
0.3765
0.3816
0.3876
Illuminance (lux)
252
254
246
245
254
Luminance ()
79
78
77
77
79
CIE-Rf
94
91
73
82
90
Table 4.
STRESS Values for Intra- and Inter-Observer Variability
Observers
1
2
3
4
5
6
7
8
9
10
11
12
Intra-Observer
27
26
15
28
21
45
22
35
35
36
29
21
Inter-Observer
38
42
38
37
46
49
29
43
30
35
31
29
Table 5.
STRESS Values for Intra- and Inter-Observer Variability, for
Each TCS Separately
Samples
HL8
JCRI
1
2
3
4
5
6
7
8
1
3
6
9
12
15
16
18
Intra-Observer
39
–
38
–
–
–
–
–
21
–
26
–
–
–
–
–
Inter-Observer
43
30
39
37
41
23
29
27
27
27
27
47
39
34
46
44
Table 6.
STRESS Values for Intra- and Inter-Observer Variability for
Each Test Source
Tested Light Sources
3000K
4000K
Fluo
LED1
LED2
LED3
Fluo
LED1
LED2
LED3
Intra-Observer
21
16
14
30
30
22
26
35
Inter-Observer
34
29
32
35
38
28
32
44
Table 7.
Mean Perceived Color Differences and Calculated Color
Differences for 2° and 2° Fundamental (2°F) Standard Observers
(Sorted by CCT Groups and Increasing Perceived Color
Differences, Average on 12 Observers and 16 TCSs)a
Perceived
CIE
CIELAB
CAM02-UCS
IPT*100
2°
2°F
2°
2°F
2°
2°F
2°
2°F
3000K Lamp Group
LED3 versus REF
1.18
9.98
9.34
4.81
4.47
3.23
3.07
4.37
4.12
FLUO versus REF
1.23
7.91
7.29
4.83
4.54
3.12
2.92
3.60
3.22
LED2 versus REF
1.58
16.56
15.37
9.14
8.87
5.85
5.66
7.46
7.06
LED1 versus REF
1.88
21.02
19.61
11.37
10.90
7.15
6.86
9.17
8.67
4000K Lamp Group
LED3 versus REF
1.02
3.83
3.61
1.88
1.94
1.23
1.22
1.68
1.58
FLUO versus REF
1.12
3.96
3.69
2.86
2.66
1.76
1.65
2.29
2.18
LED2 versus REF
1.25
10.76
10.20
6.35
6.01
3.73
3.57
4.70
4.46
LED1 versus REF
1.89
15.95
15.00
10.02
9.73
5.88
5.68
7.30
6.96
F stands for fundamental.
Table 8.
Mean Perceived Color Difference and Calculated Color
Differences for 10° and 10° Fundamental (10°F) Standard
Observers (Sorted by CCT Groups and Increasing Perceived Color
Differences, Average on 12 Observers and 16 TCSs)a
Perceived
CIE
CIELAB
CAM02-UCS
IPT*100
10°
10°F
10°
10°F
10°
10°F
10°
10°F
3000K Lamp Group
LED3 versus REF
1.18
8.01
8.01
4.44
4.43
2.87
2.88
3.64
3.64
FLUO versus REF
1.23
6.67
6.44
4.25
4.16
2.81
2.76
3.06
2.98
LED2 versus REF
1.58
13.97
14.08
9.71
9.80
5.76
5.79
6.61
6.65
LED1 versus REF
1.88
16.93
17.00
11.38
11.47
6.66
6.68
7.88
7.93
4000K Lamp Group
LED3 versus REF
1.02
3.05
3.03
1.98
2.01
1.22
1.23
1.43
1.42
FLUO versus REF
1.12
3.31
3.33
2.51
2.55
1.55
1.55
2.15
2.23
LED2 versus REF
1.25
8.39
8.34
5.90
5.90
3.32
3.30
3.98
3.98
LED1 versus REF
1.89
13.57
13.55
10.39
10.47
5.64
5.63
6.51
6.53
F stands for fundamental.
Table 9.
Color Fidelity Indices for the 10 Light Sources Used in the
Experiment
CIE-Rf
CIE-Ra
CQS-Qf
CRI- CAM02UCS
CRI2012
IES-Rf
3000K Lamp Group
3000_Ref
89
93
89
90
91
87
3000_Fluo
79
84
80
78
71
77
3000_LED3
80
74
76
79
85
78
3000_LED2
71
58
64
68
74
67
3000_LED1
64
42
53
58
65
59
4000K Lamp Group
4000_Ref
94
96
94
95
94
93
4000_Fluo
91
91
90
91
84
90
4000_LED3
90
88
89
89
90
88
4000_LED2
82
72
75
78
86
80
4000_LED1
73
60
63
66
76
69
Table 10.
Pearson Correlation Between Perceived Color Differences and
Color Fidelity Indices
P, Planckian radiator; D, Daylight illuminant; RMS, root
mean square; comb., combination.
Complementary color samples (not used in the calculation of
the general color rendering index).
Specifically selected to have high spatial and spectral
uniformities.
Table 2.
Characteristics of the 3000K Lamp Group
3000_Ref
3000_Fluo
3000_LED1
3000_LED2
3000_LED3
Booth
central
right
left
left
left
CCT (K)
2873
2954
2634
2632
2712
Duv
−0.003
−0.001
−0.009
−0.009
−0.006
0.4410
0.4390
0.4505
0.4506
0.4495
0.3968
0.4028
0.3860
0.3858
0.3934
Illuminance (lux)
254
260
254
254
257
Luminance ()
79
80
78
79
79
CIE-Rf
89
79
64
71
80
Table 3.
Characteristics of the 4000K Lamp Group
4000_Ref
4000_Fluo
4000_LED1
4000_LED2
4000_LED3
Booth
central
right
left
left
left
CCT (K)
3936
3891
3685
3786
4029
Duv
0.002
0.003
−0.003
0.000
0.004
0.3850
0.3879
0.3924
0.3900
0.3823
0.3843
0.3881
0.3765
0.3816
0.3876
Illuminance (lux)
252
254
246
245
254
Luminance ()
79
78
77
77
79
CIE-Rf
94
91
73
82
90
Table 4.
STRESS Values for Intra- and Inter-Observer Variability
Observers
1
2
3
4
5
6
7
8
9
10
11
12
Intra-Observer
27
26
15
28
21
45
22
35
35
36
29
21
Inter-Observer
38
42
38
37
46
49
29
43
30
35
31
29
Table 5.
STRESS Values for Intra- and Inter-Observer Variability, for
Each TCS Separately
Samples
HL8
JCRI
1
2
3
4
5
6
7
8
1
3
6
9
12
15
16
18
Intra-Observer
39
–
38
–
–
–
–
–
21
–
26
–
–
–
–
–
Inter-Observer
43
30
39
37
41
23
29
27
27
27
27
47
39
34
46
44
Table 6.
STRESS Values for Intra- and Inter-Observer Variability for
Each Test Source
Tested Light Sources
3000K
4000K
Fluo
LED1
LED2
LED3
Fluo
LED1
LED2
LED3
Intra-Observer
21
16
14
30
30
22
26
35
Inter-Observer
34
29
32
35
38
28
32
44
Table 7.
Mean Perceived Color Differences and Calculated Color
Differences for 2° and 2° Fundamental (2°F) Standard Observers
(Sorted by CCT Groups and Increasing Perceived Color
Differences, Average on 12 Observers and 16 TCSs)a
Perceived
CIE
CIELAB
CAM02-UCS
IPT*100
2°
2°F
2°
2°F
2°
2°F
2°
2°F
3000K Lamp Group
LED3 versus REF
1.18
9.98
9.34
4.81
4.47
3.23
3.07
4.37
4.12
FLUO versus REF
1.23
7.91
7.29
4.83
4.54
3.12
2.92
3.60
3.22
LED2 versus REF
1.58
16.56
15.37
9.14
8.87
5.85
5.66
7.46
7.06
LED1 versus REF
1.88
21.02
19.61
11.37
10.90
7.15
6.86
9.17
8.67
4000K Lamp Group
LED3 versus REF
1.02
3.83
3.61
1.88
1.94
1.23
1.22
1.68
1.58
FLUO versus REF
1.12
3.96
3.69
2.86
2.66
1.76
1.65
2.29
2.18
LED2 versus REF
1.25
10.76
10.20
6.35
6.01
3.73
3.57
4.70
4.46
LED1 versus REF
1.89
15.95
15.00
10.02
9.73
5.88
5.68
7.30
6.96
F stands for fundamental.
Table 8.
Mean Perceived Color Difference and Calculated Color
Differences for 10° and 10° Fundamental (10°F) Standard
Observers (Sorted by CCT Groups and Increasing Perceived Color
Differences, Average on 12 Observers and 16 TCSs)a
Perceived
CIE
CIELAB
CAM02-UCS
IPT*100
10°
10°F
10°
10°F
10°
10°F
10°
10°F
3000K Lamp Group
LED3 versus REF
1.18
8.01
8.01
4.44
4.43
2.87
2.88
3.64
3.64
FLUO versus REF
1.23
6.67
6.44
4.25
4.16
2.81
2.76
3.06
2.98
LED2 versus REF
1.58
13.97
14.08
9.71
9.80
5.76
5.79
6.61
6.65
LED1 versus REF
1.88
16.93
17.00
11.38
11.47
6.66
6.68
7.88
7.93
4000K Lamp Group
LED3 versus REF
1.02
3.05
3.03
1.98
2.01
1.22
1.23
1.43
1.42
FLUO versus REF
1.12
3.31
3.33
2.51
2.55
1.55
1.55
2.15
2.23
LED2 versus REF
1.25
8.39
8.34
5.90
5.90
3.32
3.30
3.98
3.98
LED1 versus REF
1.89
13.57
13.55
10.39
10.47
5.64
5.63
6.51
6.53
F stands for fundamental.
Table 9.
Color Fidelity Indices for the 10 Light Sources Used in the
Experiment
CIE-Rf
CIE-Ra
CQS-Qf
CRI- CAM02UCS
CRI2012
IES-Rf
3000K Lamp Group
3000_Ref
89
93
89
90
91
87
3000_Fluo
79
84
80
78
71
77
3000_LED3
80
74
76
79
85
78
3000_LED2
71
58
64
68
74
67
3000_LED1
64
42
53
58
65
59
4000K Lamp Group
4000_Ref
94
96
94
95
94
93
4000_Fluo
91
91
90
91
84
90
4000_LED3
90
88
89
89
90
88
4000_LED2
82
72
75
78
86
80
4000_LED1
73
60
63
66
76
69
Table 10.
Pearson Correlation Between Perceived Color Differences and
Color Fidelity Indices