Great promise, few options: Can advances in color science ... · cs,h1: indicates the . specific....

Great promise, few options:

Can advances in color science shift

the market?

Tony Esposito

January 29, 2020

Michael Royer

Lorne Whitehead

2

Optimizing Illumination

illumination

electricity

human impact

watt

well-being

well-being “joy per joule”

watt

n’s Joy per Joule

illumination

human impact

Optimizing Illumination’s Joy per Joule

quality quantity

comfort performance

illumination

human impact

quality quantity

comfort performance

illumination

human impact

quality

comfort performance

quantity

illumination

human impact

Over-Emphasizing the Easily-Measured

quality

comfort performance

quantity

- a lingering problem from the 20th century -

Over-Emphasizing the Easily-Measured- a lingering problem from the 20th century -

CIE photopic luminosity function V(λ)

Over-Emphasizing the Easily-Measured- a lingering problem from the 20th century -

20

50

2

5

.001Illuminance (fc)

9

Location Quantity Spectrum Timing Control

10

Location Quantity Spectrum Timing Control

11

SPD

Chromaticity

Relative Photoreceptor

Stimulation

LER

Color Rendition

CCT

Duv

S/P

M/P

Fidelity

Shifts

White-ness

Match

Match

Hue

Chroma

Pupil

Circa-dian

LPW

Visual Perf.

12

SPD

Chromaticity

Relative Photoreceptor

Stimulation

LER

Color Rendition

CCT

Duv

S/P

M/P

Fidelity

Shifts

White-ness

Match

Match

Hue

Chroma

Pupil

Circa-dian

LPW

Visual Perf.

14

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

v'

u'

0.0000.0050.0100.0150.0200.0250.0300.0350.040

380 480 580 680 780

Spec

tral

Pow

er (W

/nm

)

Wavelength (nm)

RedLimeAmberGreenCyanBlueIndigo

16

RfRg

Rcs,h1Rt

CRIR9

M/PS/P

LER

68 – 9479 – 120-19% – 26%88 – 9643 – 95-120 – 980.6 – 1.11.4 – 2.2286 – 352

0.0000.0020.0040.0060.0080.0100.0120.0140.0160.018

380 430 480 530 580 630 680 730 780

Spec

tral

Pow

er (W

/nm

)

Wavelength (nm)

2700 K3000 K3500 K4000 K5000 K6500 K

Nominal CCTNormalized for Equal Lumens

17

Status Quo: Given a CCT and minimum color fidelity, maximize lumens/watt.

18

S/P = M/P = CRI = R9 =

LER = LPW ≈

S/P = M/P = CRI = R9 =

LER = LPW ≈

1.40.7100991515

1.10.482-836080

S/P = M/P = CRI = R9 =

LER = LPW ≈

1.20.58112310130

19

What will it take to changethe status quo?

New metrics?Induce demand / does anyone care?Material R&D?Patent barriers?Cost?Reevaluation of Tradeoffs?

How Vision Senses Surface Colors


A Surface’s Color Relates to its Spectral Reflectance Function

Wavelength

Ref

lect

ance

“IncreasingLightness”


Lightness:



Wavelength

Ref

lect

ance

“Blue to Orange”

“Changing Average

Slope”

Blue

Orange



Wavelength

Ref

lect

ance

“Purple to Green”

“Changing AverageCurvature”

Purple

Green

“white” light

“gray” surface

orange reflection!

Poor Rendering is Due to Spectral Interference !

FACTS ABOUT COLOR RENDERING AND SOME COMMON MISCONCEPTIONS

1. The IES/CIE Color Fidelity Index Is a number less than or equal to 100, but it is not a percentage.

2. If two objects look the same under daylight, they may not match under a poor color rendering source.

3. Lamps with the same color rendering score may have very different SPDs and cause different shifts.

FACTS ABOUT COLOR RENDERING AND SOME COMMON MISCONCEPTIONS

4. People cannot adapt to poor color rendering

5. Color rendering cannot be judged by looking directly at a light source.

6. Light source color rendering is a completely different property than light source color.

Rf

∆Rf

Consider An Important Design Choice:

Most often, most designers select Design AYet usually, Design B is better for occupants

Design A acceptable acceptable 90 80Design B same as A same as A 80 90

Installed Cost

Power Consumed

Light Quantity

Light Quality

Sheet1

Installed CostPower ConsumedLight QuantityLight Quality

Design Aacceptableacceptable9080

Design Bsame as Asame as A8090

A look to the future:

Excellent Color Rendering (nearly) Everywhere

Requiring: Excellent Metrics for Color Rendering

45

ANSI/IES TM-30-18

46

What is it?

47

“Effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant.”

- International Commission on Illumination (CIE)

Color rendition is relative

Review: color rendering, defined

48

Test Source

Reference Source

Δ1 Δ2 Δ3 Δ4 Δ5 Δ6 Δ7 Δ8

Color rendition is relative

49

Perfect Fidelity

Limitation of considering only color fidelity

50

CRI = 80 CRI = 80

Increase Saturation

DecreaseSaturation


51

CRI = 80

CRI = 80

Positive Hue Shift

Negative Hue Shift

Increase Saturation

DecreaseSaturation


52

Increase Saturation

DecreaseSaturation

Positive Hue Shift

Negative Hue Shift

Constant Fidelity (CRI)


53

EQ EQ EQ EQ

Rf,h1100

Rf,h180

Rf,h160

Rf,h180

Rf,h160

(Color appearances not accurate. For educational purposes only)


Rcs,h10%

Rcs,h1+8%

Rcs,h1+15%

Rcs,h1-8%

Rcs,h1-15%

54

How many metrics are contained within TM-30?

55

At least 149(1) Average Color Fidelity, Rf(1) Average Gamut Area, Rg(16) Local Chroma Shift, Rcs,hj(16) Local Hue Shift Rh1,hj(16) Local Color Fidelity, Rf,hj(99) Sample Color Fidelity, Rf,CESi

How many metrics are contained within TM-30?

56

How many should be minimally considered?

57

How many should be minimally considered?

58

Average Fidelity, Rf: indicates the average deviation from the source’s reference illuminant. It only indicates the magnitude of the difference, not the direction.

Average Gamut Area, Rg: indicates the average increase or decrease in saturation relative to the source’s reference illuminant.

Local Color Fidelity Hue Bin 1 (Red), Rf,h1: indicates the specific deviation, relative to the source’s reference illuminant, for red hues.

Local Chroma Shift, Rcs,h1: indicates the specific increase or decrease in saturation, relative to the source’s reference illuminant, for red hues.

e.g. “CRI”

e.g. CQS QgGAI

e.g. R9

e.g. None

The main 4 metrics

59

Metric Quizzzzzzzzzzzz

60

What can we say about this point?

Rf = 87, Rg = 109

Rf = 87

Rg = 109

This light source causes distortions relative to ref source (don’t know direction of distortion)

This light source, ON AVERAGE, increases the saturation of objects (relative to ref source). We don’t know which hues are being enhanced.

TM-30 Metric Quiz

61

Relative to the ref source, this light source is:

• Increasing the average saturation of RED hues (Rcs,h1 = + 11%)

• Slightly increasing the saturation of green and yellow-green hues (Rcs,h6 = +4%)

• Rf,h1 < 100

What can we say about this point?

Rf = 87, Rg = 109

TM-30 Metric Quiz

63

What is it?

64

MeasureAverage Color fidelity

Red Fidelity (hue bin 1)

Gamut area

Gamut shape/Specific color shifts

(specifically red)

SymbolRf

Rf,h1Rg

CVGRcs,h1

CharacteristicFidelity

Preference(object and skin)

Vividness

IES TM-30 ANNEX E

65

Design IntentThe desired effect of color rendition on the illuminated environment.

Preference (P) Vividness (V) Fidelity (F)

Prio

rity

Leve

lTh

e ba

lanc

e be

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low

ing

trade

offs

and

incr

easi

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e lik

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ood

of m

eetin

g th

e de

sign

inte

nt. 1 P1

Rf ≥ 78

V1

Rg ≥ 118

F1 Rf ≥ 95Rg ≥ 95 Rcs,h1 ≥ 15%

-1% ≤ Rcs,h1 ≤ 15%

2 P2

Rf ≥ 75

V2

Rg ≥ 110

F2

Rf ≥ 90

Rg ≥ 95 Rcs,h1 ≥ 6% Rf,h1 ≥ 90

-7% ≤ Rcs,h1 ≤ 15%

3 P3

Rf ≥ 70

V3

Rg ≥ 100

F3

Rf ≥ 85

Rg ≥ 88 Rcs,h1 ≥ 0% Rf,h1 ≥ 85

-12% ≤ Rcs,h1 ≤ 18%

IES TM-30 ANNEX E

66



Prio

rity

Leve

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low

ing

trade

offs

and

incr

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ng th

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eetin

g th

e de

sign

inte

nt. 1 P1

Rf ≥ 78

V1

Rg ≥ 118

F1 Rf ≥ 95Rg ≥ 95 Rcs,h1 ≥ 15%

-1% ≤ Rcs,h1 ≤ 15%

2 P2

Rf ≥ 75

V2

Rg ≥ 110

F2

Rf ≥ 90

Rg ≥ 95 Rcs,h1 ≥ 6% Rf,h1 ≥ 90

-7% ≤ Rcs,h1 ≤ 15%

3 P3

Rf ≥ 70

V3

Rg ≥ 100

F3

Rf ≥ 85

Rg ≥ 88 Rcs,h1 ≥ 0% Rf,h1 ≥ 85

-12% ≤ Rcs,h1 ≤ 18%

Assumptions: 200-700 lux, polychromatic environment, single chromaticity

IES TM-30 ANNEX E

67



Prio

rity

Leve

lTh

e ba

lanc

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twee

n al

low

ing

trade

offs

and

incr

easi

ng th

e lik

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eetin

g th

e de

sign

inte

nt. 1 P1

Rf ≥ 78

V1

Rg ≥ 118

F1 Rf ≥ 95Rg ≥ 95 Rcs,h1 ≥ 15%

-1% ≤ Rcs,h1 ≤ 15%

2 P2

Rf ≥ 75

V2

Rg ≥ 110

F2

Rf ≥ 90

Rg ≥ 95 Rcs,h1 ≥ 6% Rf,h1 ≥ 90

-7% ≤ Rcs,h1 ≤ 15%

3 P3

Rf ≥ 70

V3

Rg ≥ 100

F3

Rf ≥ 85

Rg ≥ 88 Rcs,h1 ≥ 0% Rf,h1 ≥ 85

-12% ≤ Rcs,h1 ≤ 18%


IES TM-30 ANNEX E

68



Prio

rity

Leve

lTh

e ba

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twee

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low

ing

trade

offs

and

incr

easi

ng th

e lik

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eetin

g th

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sign

inte

nt. 1 P1

Rf ≥ 78

V1

Rg ≥ 118

F1 Rf ≥ 95Rg ≥ 95 Rcs,h1 ≥ 15%

-1% ≤ Rcs,h1 ≤ 15%

2 P2

Rf ≥ 75

V2

Rg ≥ 110

F2

Rf ≥ 90

Rg ≥ 95 Rcs,h1 ≥ 6% Rf,h1 ≥ 90

-7% ≤ Rcs,h1 ≤ 15%

3 P3

Rf ≥ 70

V3

Rg ≥ 100

F3

Rf ≥ 85

Rg ≥ 88 Rcs,h1 ≥ 0% Rf,h1 ≥ 85

-12% ≤ Rcs,h1 ≤ 18%


IES TM-30 ANNEX E

69



Prio

rity

Leve

lTh

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twee

n al

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trade

offs

and

incr

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e lik

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sign

inte

nt. 1 P1

Rf ≥ 78

V1

Rg ≥ 118

F1 Rf ≥ 95Rg ≥ 95 Rcs,h1 ≥ 15%

-1% ≤ Rcs,h1 ≤ 15%

2 P2

Rf ≥ 75

V2

Rg ≥ 110

F2

Rf ≥ 90

Rg ≥ 95 Rcs,h1 ≥ 6% Rf,h1 ≥ 90

-7% ≤ Rcs,h1 ≤ 15%

3 P3

Rf ≥ 70

V3

Rg ≥ 100

F3

Rf ≥ 85

Rg ≥ 88 Rcs,h1 ≥ 0% Rf,h1 ≥ 85

-12% ≤ Rcs,h1 ≤ 18%


IES TM-30 ANNEX E

70

Important Notes• The Assumptions are important!

• 200 – 700 Lux• Polychromatic Environment• Single Chromaticity

• PVF categories ARE NOT INDEPENDENT. P1V1F1 is not possible

• ANNEX E does not specifically consider the rendition of skin tones

IES TM-30 ANNEX E

71

So What?

72

F1

F2

F3

All Theoretical SPDsTheoretical SPDs with Ra ≥ 80 and R9 ≥ 0Theoretical SPDs with Ra ≥ 90 and R9 ≥ 50

Commercially-Available LED SPDs

IES TM-30 ANNEX E: Color Fidelity

73

P1*P2*P3*

IES TM-30 ANNEX E: Color Preference

74

Summary, TM-30 and ANNEX E• IES TM-30 is a unified system of objective measures that capture color difference

• Specifically, TM-30 provides measures beyond average fidelity and average gamut area that provide information about hue-SPECIFIC color shifts

• IES TM-30 ANNEX E was developed to facilitate the ease of use of TM-30 and to help specifiers flex color rendition as a parameter in their designs

• And, potentially, as a way for manufacturers to differentiate their products

• TM-30 helps illustrate the tradeoff between luminous efficacy and red rendition, and shows that many commercially available sources desaturate red colors

• TM-30 can be used in an optimization routine to produce sources with a spectrum that is more purposefully tuned to the intended application

75

Metameric Uncertainty

https://www.astroml.org/book_figures/chapter3/fig_bivariate_gaussian.html

76



Gamut area


(specifically red)

SymbolRf

Rf,h1Rg

CVGRcs,h1



Vividness


77



Gamut area


(specifically red)

Light Source Error Score

Metameric Uncertainty Index

SymbolRf

Rf,h1Rg

CVGRcs,h1

RdRt



Vividness

Color Discrimination

Metameric Mismatch

IES TM-30


78

What is metamerism?Metameric SourcesSources that have different SPDs, but the same chromaticity.They have the same appearance when viewed directly.

Metameric ObjectsSources that have different “Practical Colors” (SPD*SRD), but the same chromaticity.They have the same appearance when viewed directly.

79

Why is it so uncertain?

80

Who cares?

81

Metameric Mismatch

https://www.xrite.com/blog/two-essential-components-color-programhttps://store.nike.com/us/en_us/product/air-force-1-high-essential-id/

https://www.chick-fil-a.com/menu-items/coca-cola

https://www.socialbakers.com/statistics/twitter/profiles/detail/71026122-mcdonaldshttps://apps.apple.com/us/app/t-mobile/id561625752

https://twitter.com/starbuckshttps://www.facebook.com/

82

Metameric Mismatch

“The sensitivity of the strips on clinical urine specimens may vary depending upon several factors, such as the variability of color perception, specific gravity, pH value, and the lighting conditions when the strips are read visually.”

83

We want to know,

What is the likelihood that a light source will cause a mismatch between objects that were previously metameric (with respect to a given illuminant)

84

Metameric Uncertainty Index, Rt

85

Matching greenunder 5000 Kdaylight

Wavelength (nm)

R R R

Matching blueunder 5000 Kdaylight

Matching redunder 5000 Kdaylight

Wavelength (nm) Wavelength (nm)

SRDs that are metameric with respect to D50

86


87


88

SRDs redistribute when the source is changed

89


91


92


93

Actual color shift is dissected into two pieces

“Actual Color Shift”

94

“Base Color Shift”

“Metameric Color Shift” “Actual Color Shift”

Actual color shift is dissected into two pieces

95


100 Rt

96


High Rt

97


Low Rt

98

Summary, Rt• Light source-induced color shifts divided into two components:

• base color shift, following a regular pattern

• metameric color shift, which is random

• These can be quantified using the 99 IES TM-30 samples and a vector field model for estimating base color shift

• Metameric color shift intensity is new useful information

• It can be converted into Rt, the Metameric Uncertainty Index

• This can be useful in situations where metamerism matters

• Next steps for Rt include psychophysical experimentation. Does Rt actually measure what we think it does?

99

Great promise, few options: Can advances in color science shift the market?

100

S/P = M/P = CRI = R9 =

LER = LPW ≈

S/P = M/P = CRI = R9 =

LER = LPW ≈

1.40.7100991515

1.10.482-836080

S/P = M/P = CRI = R9 =

LER = LPW ≈

1.20.58112310130

101Royer M. Evaluating tradeoffs between energy efficiency and color rendition, OSA Continuum 2, 2308-2327 (2019)

102

CRI = R9 =

LER =

9572290

CRI = R9 =

LER =

1009915

CRI = R9 =

LER =

9798260

103

CRI = R9 =

LER =

9296315

CRI = R9 =

LER =

771513

CRI = R9 =

LER =

8646250

104

CRI = R9 =

LER =

9124380

CRI = R9 =

LER =

7943398

CRI = R9 =

LER =

8321311

105

Lightening Round:What’s Next In Color Science

• Updating Chromaticity• Observer Variability• Color Discrimination• Color Rendition Variability• Far Red• Light Level Variation• Tuning for Visually Impaired

106

Last Word• What’s your vision for the future?• What’s wrong with the status quo?

Great promise, few options: Can advances in color science shift the market?Optimizing Illumination's Joy per JouleOver-Emphasizing the Easily-MeasuredStatus QuoWhat will it take to change the status quo?How Vision Senses Surface ColorsFACTS ABOUT COLOR RENDERINGAND SOME COMMON MISCONCEPTIONSConsider An Important Design Choice:UntitledANSI/IES TM-30-18What is it?Review: color rendering, definedColor rendition is relativeLimitation of considering only color fidelityHow many metrics are contained within TM-30?How many should be minimally considered?The main 4 metricsMetric QuizzzzzzzzzzzzTM-30 Metric QuizAnnex EWhat is it?IES TM-30 ANNEX ESo What?IES TM-30 ANNEX E: Color FidelityIES TM-30 ANNEX E: Color PreferenceSummary, TM-30 and ANNEX EMetameric UncertaintyWhat is metamerism?Why is it so uncertain?Who cares?Metameric MismatchWe want to know,Metameric Uncertainty Index, RtSRDs that are metameric with respect to D50SRDs redistribute when the source is changedActual color shift is dissected into two piecesMetameric Uncertainty Index, RtSummary, RtGreat promise, few options:Lightening Round:What’s Next In Color ScienceLast Word

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