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

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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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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

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CR

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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.