exploring the concepts of color and gloss...exploring the concepts of color and gloss jeralyn camp...

Exploring the Concepts of Color and Gloss

Jeralyn CampBYK Gardner

May 2-3, 2016

Color stimulates certain Feelings!

Color stands for Identification!

Color stands for Regulation and Authority!

Color influences our Purchasing Decisions!

Uniform Color : Multi-component Products

Visual Assessment

• Color perception is subjective- Age, gender, mood

• We cannot communicate nor remember colors- Only names or numbers

• Color is dependent on surrounding light

• Color is dependent on background

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Page 9, BYK-Gardner USA, Color Measurement

Colors seem more dramatic against black

Colors seem more subdued against white

Color Perception Light Source

Object

Observer

D65 / 10°spectro-guide 45/0

Color Scale Standard Sample Differences

L* 36.84 37.77 0.93a* -24.10 -24.59 -0.49b* 12.00 11.88 -0.12

dE* = 1.05

Measurement Report illuminant

Spectrum of Visible Light object

Wavelength l (nm)

1 nm = 10-9 m

UV IR

White light is a mixture

of many colors

Standard illuminants

400 500 600 700

Wavelength [nm]

F2E l

400 500 600 700

Wavelength [nm]

E l

A

400 500 600 700

Wavelength [nm]

E l

D65

North Sky Daylight Tungsten Fluorescent

Ojects look different under different illuminants

D65 / 10°spectro-guide 45/0

Color Scale Standard Sample Differences

L* 36.84 37.77 0.93a* -24.10 -24.59 -0.49b* 12.00 11.88 -0.12

dE* = 1.05

Measurement Report observer

Eye Detectors

Cone cells

Color detectors

Rod cells

Lightness detectors at night

Cones

Retina

Rods

Cones

Cones

Young/Helmholtz Color Theory

Primary wavelengths:700 nm (red)546 nm (green) 435 nm (blue)

Wright / Guild Experiment

Observer

Masking Screen

Black Partition

The Eye and Fields of View

2° observer (1931)

• Small area of the retina

• Does not agree with color viewing

10°

10° observer (1964)

• Large area of the retina

• Corresponds with color viewing

Standard Observer

10° Observer (1964)

2° Observer (1931)

400 500 600 700

Wavelength (nm)

Rela

tive

En

erg

y

•Dichromacy: only 2 cones are functioning• Red blindness (approx. 1% of male)

• Green blindness (approx. 1% of male)

• Blue blindness (very seldom: 1-2 in 100,000)

•Anomalous Trichromacy: 3 cones – 1 cone is altered• Most popular case (approx. 5.9 % male) e.g. red-green deficiency

Ishihara`s Test for color deficiency

Color Perception Light Source

Object

Observer

Opaque Samples

Incident Light

Specular Reflection

(= Gloss)Diffused Reflection

Opaque Samples: Absorption and Diffusion of Light

Incident light

Specular Reflection

(= Gloss)Diffused Reflection

Object Color Spectral Reflectance Curves

yellow

red

green

blue

The Building Blocks of Color

× ×

Illuminant

400 500 600 700

Wavelength [nm]

E l

AA

Observer

2°

Object

Color Scales: X Y Z L*a*b*, ....

Opponent Color Theory

B

R

A

I

N

Blue detectors

Blue - Yellow Signal

Black - White

Signal

Red - Green Signal

Green detectors

Red detectors

Page 29, BYK-Gardner GmbH, Color Measurement

Page 30, BYK-Gardner GmbH, Color Measurement

CIE L*a*b*-SystemL* Lightness

a* green / red

b* blue/yellow

L* Lightness

C* Chroma(saturation)

h° hue angle

CIELab - System

L* = + 58,12

C* = + 47,32

h° = 50°

L* = 0

L* = + 58,12

a* = + 36,26

b* = + 30,41

L* = 100

+a*

-a*

+b*

-b* Blue

Red

Green

Yellow

D65 / 10°spectro-guide 45/0

Color Scale Standard Sample Differences

L* 36.84 37.77 0.93a* -24.10 -24.59 -0.49b* 12.00 11.88 -0.12

dE* = 1.05

Measurement Report scales

Metamerism – 2 samples: pigments with different reflectance

D65 Daylight

match

A Tungsten

mismatch

% Reflectance

Metamerism Index MI

< 1 (spectrum needed)

Instrument´s Display of MetamerismD65/10°

dL* = 0,10

da* = 0,05

db* = 0,05

dE* = 0,12

A/10°

dL* = 0,08

da* = -1,04

db* = 0,10

dE* = 1,04

F11/10°

dL* = 0,06

da* = -1,62

db* = 0,06

dE* = 1,62

Metamerism Index

D65/10° - F11/10° 1,64

D65/10° - A/10° 1,06

F11/10° - A/10° 0,57

Limitations of CIELab System

Standard

Sample 1

E * = 0.57 0.57 0.57 = 12 2 2

Sample 2

E * = 0.0 1.0 0.0 = 12 2 2

E* = (L*)2 + (a*)2 + (b*)2

Limitations of CIELab SystemMeasured values do not correlate with visual impression

• Visual acceptability is based on ellipses not circles: Tolerances for hue are tighter than for chroma

• Chromatic colors have larger tolerances than pastels or near neutrals

• Size and shape of ellipse change dependent on the hue: Acceptable color differences vary from color to color Green has larger tolerances than dark blue

All colors within one ellipse are perceived as the same color.

Rectangular versus Elliptical Tolerances

± a*

Product Standard

Acceptable Match

± b*

Visually Rejected Match

Improvements of CIELab System

•Goal:• Better agreement with visual color perception

• One tolerance for all colors = uniform color space

dE*CMC

DIN99dE00

dE*94

ECMC – Color Measurement Committee of The Society of Dyers and Colorists (UK): 1988

• Based on visual evaluation of textile samples

• Currently specified in the following standards:- British Standard BS6923- American AATCC Test Method 173- ISO International Standard 105-J03

• Based on elliptical (not rectangular) spacing and L*C*H*

• Corrects for chroma, hue and lightness dependent perception

ECMC – Color Difference Formula

• 3-dimensional ellipsoid with axes corresponding to

hue, chroma and lightness

• Weighting factors (= semi-axis) SL, SC and SH

are dependent on color of standard

• Application factors l and c to modify the lengths of

semi-axes

212

ab

2

ab

2

:CMC

*H*C*LE

=

HCL

clScSlS

÷ ÷÷

lSL

HS

ccS

ECMC – Color Difference Formula

dECMC (l:c) = dL*

lSL( )2

+(dC*ab

cSC )2

+ )dH*ab

SH

2

(Where SL = 0.040975 L1 Sc = 0.0638 C1 + 0.638

1 + 0.01765 L1 1 + 0.0121 C1

Unless L1 < 16 when SL = 0.511

And SH = SC (Tf + 1- f) where f = (C1)4 1/2

(C1)4 + 1900( )

T = 0.36 + 0.4*cos( h1 + 35) unless h1 is between 164 and 345 when:

T = 0.56 + 0.2*cos( h1 + 168) where L1, C1 and h1 relate to the standard

ECMC – Color Difference Formula Better correlation to visual perception: Brilliant Yellow with Chroma / ΔHue

Chromatic colors have larger visual

tolerances in chroma than in hue

Color Difference: dE*dL*=1, dC*=1.3, dH*=0.65

Color Difference: dECMC

-4

-3

-2

-1

0

1

2

3

4

-4 -3 -2 -1 0 1 2 3 4

-4

-3

-2

-1

0

1

2

3

41

Standard; STANDARD 07

L*=84.25; a*=5.74; b*=96

45°

-dL*

+dL*+db*

-db*

+da*-da*

L* a* b* dL* da* db* dC* dH*

Standard YellowYellow -HYellow -CYellow +C

dE*

3.18 2.92 3.43

dECMC

1.64 0.88 1.02

84.25 5.74 96.0084.46 8.88 96.49 0.22 3.14 0.49 0.7384.52 5.75 93.09 0.27 0.01 -2.91 -0.1984.37 5.86 99.42 0.12 0.12 3.43 0.08

-4

-3

-2

-1

0

1

2

3

4

-4 -3 -2 -1 0 1 2 3 4

-4

-3

-2

-1

0

1

2

3

42

45°

-dL*

+dL*+db*

-db*

+da*-da*

ECMC – Color Difference Formula Better correlation to visual perception: Brilliant Red with C* vs. Brown (Less chromatic Red) with C*

Color Difference: dECMC

-4

-3

-2

-1

0

1

2

3

4

-4 -3 -2 -1 0 1 2 3 4

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

1

Standard; STANDARD 09

L*=38.83; a*=33.35; b*=26.67

45°

-dL*

+dL*+db*

-db*

+da*-da*

dECMC

1.13

38.83 33.35 26.67

L* a* b* dL* da* db* dC* dH* dE*

Std Brown

Brown -C 38.69 31.14 25.21 -0.14 -2.21 -1.46 0.24 2.65

-4

-3

-2

-1

0

1

2

3

4

-4 -3 -2 -1 0 1 2 3 4

-4

-3

-2

-1

0

1

2

3

41

Standard; STANDARD 08

L*=38.64; a*=64.26; b*=52.16

45°

-dL*

+dL*+db*

-db*

+da*-da*

Color Difference: dECMC

dECMC

0.84

38.64 64.26 52.16

L* a* b* dL* da* db* dC* dH* dE*

Std Brilliant Red

Brilliant Red -C 38.59 62.06 51.11 -0.05 -2.20 -1.05 0.58 2.44

Chromatic colors have larger visual tolerance than achromatic colors.

ECMC – Color Difference Formula; Influence of ratio l : c• Ratio l:c allows for a weighting of lightness to chroma

• Most common ratio: 2:1Variation in lightness can be double

compared to chroma variations

C*H*

ratio 1:1

C*

H*

ratio 2:1

L*

L*

ECMC – Color Difference FormulaInfluence of Commercial Factor: cf

• Commercial Factor (cf) determines the overall size of the ellipse

• cf sets the color tolerance: ECMC < cf PASS

ECMC > cf FAIL L*

C*

H*

cf=1.0

L*

C*

H*

cf=0.5

ECMC – Color Difference FormulaInfluence of Commercial Factor: cf

cf = 0.5

-2

-1,5

-1

-0,5

0

0,5

1

1,5

2

-2 -1,5 -1 -0,5 0 0,5 1 1,5 2

-2

-1,5

-1

-0,5

0

0,5

1

1,5

22

Standard; STANDARD 01

L*=61,62; C*=3,47; h°=263,97

45°

-dL*

+dL*+db*

-db*

+da*-da*

cf = 1.0

-2

-1,5

-1

-0,5

0

0,5

1

1,5

2

-2 -1,5 -1 -0,5 0 0,5 1 1,5 2

-4

-3

-2

-1

0

1

2

3

42

Standard; STANDARD 01

L*=61,62; C*=3,47; h°=263,97

45°

-dL*

+dL*+db*

-db*

+da*-da*

cf = 1.5

-2

-1,5

-1

-0,5

0

0,5

1

1,5

2

-2 -1,5 -1 -0,5 0 0,5 1 1,5 2

-4

-3

-2

-1

0

1

2

3

42

Standard; STANDARD 01

L*=61,62; C*=3,47; h°=263,97

45°

-dL*

+dL*+db*

-db*

+da*-da*

ECMC – Color Difference Formula Summary

• One tolerance for all colors: cf = size of the tolerance ellipse

• Tolerance is based on elliptical spacing

Size and shape of tolerance ellipse is calculated based on Standard location in the color space

0.51245°

Solids

cfcl

ECMC - Typical Tolerances

E00 (CIEDE2000) - Color Difference Formula:2001

• Based on several already existing data sets

• Currently published in the following CIE recommendation:- CIE Technical Report 142: Improvement to industrial colour difference evaluation

• Based on elliptical spacing and L*C*H*

• Corrects for lightness, chroma and hue dependent perception

ECMC – Color Difference Formula Summary

• Better correlation to visual perception:

• Chromatic Colors: Larger visual tolerance ellipse ECMC smaller for chromatic colors than for achromatic colors

(C* and H* are weighted less) compared to E*

• Light Colors: Larger visual tolerance ellipse for lightness ECMC smaller for light colors than for dark colors

(L* is weighted less) compared to E*

• Visual acceptability most sensitive to 1. Hue – 2. Chroma – 3. Lightness (l:c:h = 2:1:1)

E00 - Color Difference Formula

• Difference components L’, C’, H’:

• L’ = L’b - L’s• C’ = C’b - C’s

• where: h’ = h’b - h’s

=

2

'sin''2'

hCCH sb

Weighted color difference part

• Not the regular CIELAB components

L*, C*, H* are used, but the primed

components L’, C’, H’

b = Batch = Sample

s = Standard

= Sample - Standard

=

HHCC

T

HHCCLL SK

H

SK

CR

SK

H

SK

C

SK

LE

'''''222

00

Rotation functionWeighted color difference

E00 - Color Difference Formula

Weighted color difference part

• Improves agreement with visual color

difference perception for neutral colors

• For low chroma colors „G“ increases the

modified a‘ compared to the regular a*

• At higher chroma color a‘ approaches a*

Modification of a* (red-green) axis:

L’= L*

a’ = a* (1 + G)

b’ = b*

22 ''' baC =

=

'

'tan' 1

a

bh

=

77

7

25*

*15.0

ab

ab

C

CG

=

HHCC

T

HHCCLL SK

H

SK

CR

SK

H

SK

C

SK

LE

'''''222

00

E00 - Color Difference Formula

=

HHCC

T

HHCCLL SK

H

SK

CR

SK

H

SK

C

SK

LE

'''''222

00

77

7

25'

'2

=

C

CRC

=

2

25

275'exp30

h

CT RR = 2sin

Rotation function

• Interaction between chroma and hue

difference in blue region (275° ± 25°)

Main influence for high chroma blue

colors

Tilt of major axis of the tolerance

ellipse in the counter-clockwise

directionPhilipp Urban, Mitchell Rosen and Roy Berns: Constructing Euclidean Color

Spaces Based on Color Difference Formulas IS&T/SID Color Imaging Conference,

pp. 77-82, Albuquerque, New Mexico (2007) PDF

E00 - Color Difference Formula

=

HHCC

T

HHCCLL SK

H

SK

CR

SK

H

SK

C

SK

LE

'''''222

00

• Weighting functions to account for

variation in visual color difference

sensitivity dependent on

lightness – chroma - hue

=

2

2

50'20

50'015.01

L

LSL

)('045.01 CSC =

63'4cos20.06'3cos32.0'2cos24.030'cos17.01 = hhhhT

TCSH = '015.01

E00 - Color Difference Formula

=

HHCC

T

HHCCLL SK

H

SK

CR

SK

H

SK

C

SK

LE

'''''222

00

kL = kC = kH = 1 for reference conditions

• Application factors kL, kC, kH to correct for variations in reference conditions:- Illumination: D65- Illumination intensity: 1000 lx- Background field: uniform, neutral grey with L* = 50- Viewing field: > 4°- Sample:

- Homogeneous color without apparent pattern- Direct edge contact between sample and standard- Color difference 1 - 5 CIELAB units

Chroma Circles

colors on the same circle

have the same chroma value

Hue Lines

colors on the same line

have the same hue value

+ b*

90°

+ a*

0°-a*

180°

h°

-b*

270°

CIELAB - System: L*C*h°- Coordinates

Appearance - Gloss

Focus on Reflected Image

Haze Gloss DOI

Image Forming Quality

How is Gloss Perceived?

ObserverIllumination

Smooth Surface

How is Gloss Perceived?

ObserverIllumination

Rough Surface

Glossmeter Design

Defined angles of gloss

20°

85°

60°

Angles of IlluminationSemi GlossLow Gloss High Gloss

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12 13

85°

60°

20°

Recommended Geometries

Recommended geometryGloss level

Semi gloss

High gloss

Low gloss

60° value

10 to 70 units

> 70 units

< 10 units

60° geometry

20° geometry

85° geometry

Specular Gloss: Dependent on curvature

Specular Gloss:Dependent on coating material

20°

Gloss

Example: 1K versus 2 K

Refractive index

1.541.521.51 1.531.50

80

85

90

95

1 K

2 K

Visual:

Same brilliance

No correlation

Thank you for your attention!

Jeralyn CampBYK Gardner

May 2-3, 2016