Post on 14-Jan-2016
A data set for evaluating colour rendering property of
sources
Ronnier Luo
June 2010
Colour Rendering Index
Calculating XYZ
(XYZ)-T
Ref. ill (SPD)Test Source (SPD) CCT
(XYZ)-R
vK-CAT
(XYZ)-TR U*V*W*
CIE-CRI=Σ(100-4.6Ei)/8
Calculating XYZ
CAM02-UCS
(XYZ)-T
Ref. ill (SPD)
Ri
Test Source (SPD) CCT
(XYZ)-R
CRI-CAM02UCS=Σ(100-8Ei)/8
More information could be useful than just a single CRI number
CQS Gamut plot Vector diagram R1 = E*ab/C*r
R2 = Ch*ab/C*r
Peter van der Burgt, Communication of colour rendering property of light sources
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a*
b*
CIELAB
D65
A
S B
S B
Metamerism
D65
A
Colour Inconstant (B)
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Sample A
Sample B
Colour Inconstancy and Metamerism
CRI (Lamp quality) CII (Sample quality)
R Calculating XYZ
(XYZ)-T (XYZ)-R
CAT02
(XYZ)-TR E00
Ref. ill (D65, SPD)Test Ill. (A, SPD)
Calculating XYZ
(XYZ)-T
Ref. ill (SPD)Test Source (SPD) CCT
(XYZ)-R
vK-CAT
(XYZ)-TR U*V*W*
CIE-CRI=Σ(100-4.6Ei)/8
E(U*V*W*)
Ri
CII: SO 105-J05 (2007), Textiles-tests for colour fastness – Part J05: method for the instrumental assessment of the colour inconstancy of a specimen with a change in illuminant
Colour inconstancy of Munsell samples
Datasets No. C*(D65)CII
CIE-CRI (Ra) 8 31 2.4NIST 15 54 3.8
Inter-obs. uncertainty in the data sets for developing CAT is about 3.0 E00 units.
Munsell
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Region
mean(A)mean(F11)mean(WLED)mean(RGBLED)mean(LEDON)mean(FL4)
Generating a dataset
The data sets used Munsell (1562 paint samples) Philips (215 samples) PCCS (1063 cotton samples)
The lamps used: WLED, LEDON, ICD, CFL Optimisation criteria:
Average CII about 3.0, More samples (36 samples around hue scale), Larger colour gamut (higher C* range), and Smooth gamut boundary (L* and C* ≤10 for
neighbouring samples).
Datasets (4 lamps: WLED, LEDON, ICD, CFL)
Datasets No. C*(D65) CII Maxi (WLED)
CIE-CRI (Ra) 8 31 2.4 4.0NIST 15 54 3.8 8.1MCCC 24 34 2.4 7.9New 36 47 3.1 6.4
Observer variety in CA data set is about E00 of 3.0.
A new dataset
Low CRI Large gamut Smooth gamut Colour shift Gamut difference
36 Munsell
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h*
C*
C*
36 Munsell
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h*
L*
L*
36 Munsell
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a*
b*
Trend of colour shifts
FL4 RGB LED
LEDONICD
CDT Demonstration
Change of colour area (GAI)
Similar gamuts from different datasets under WLED
Philips Munsell PCCS
No matter which data set is used, the samples found
are quite similar for a fixed lamp.
Luo et al’s Results
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Va
lues
of
CIE
CR
I
CIE-8
CIE-14
NIST
GMCC
Gamut0
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GM VV PH ZTB WLED TLED
CIE-8
CIE-14
NIST
GMCC
Gamut
Six lamps were tested using 5 datasets: Ra(8), Ri(14), NIST(15), MCCC(24) and Boundary (684).
Similar CRIs’ performance regardless the datasets used.