Let‘s talk about Colorimetric Basics · Colorimetric Basics . Textile Effects Electro-Magnetic Waves visible light . Textile Effects Different technics of color mixtures Subtractive

Let‘s talk about Colorimety

Textile Effects

Let‘s talk about Colorimetric Basics

Textile Effects

Electro-Magnetic Waves

visible light

Textile Effects

Different technics of color mixtures

Subtractive

color mixture

e.g. used for

textile dyeing or

printing

Additive color

mixture

e.g. used for TV

or computer

screens or

paper graphics

Textile Effects

Relation between reflectance and absorbance

textile sample

light source human eye

The light is either reflected or absorbed by the sample

Textile Effects

Reflectance

The reflectance factor is the ratio of the reflected light Ir to

the illuminating light I0

%R 100

Reflectance

in %

I

Ir

0

Reflectance

factor beta

Textile Effects

Absorbance

Both, reflectance and absorbance, are relative factors and

independant from the energy distribution of the illuminant

Absorbance

in %

1001A %

Absorbance

factor

1A

The absorbance factor is the difference between the total,

illumuninating light and the reflected light

Textile Effects

Reflectance Curves/1

Reflectance curce of a yellow shade

0

0.2

0.4

0.6

0.8

1

400 500 600 700

Wavelength [nm]

Re

fle

cta

nc

e fa

cto

r b

eta

absorbed light

reflected light

Reflectance curve of a red shade

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

400 500 600 700

Wavelength [nm]

Re

fle

cta

nc

e fa

cto

r b

eta

absorbed light

reflected

light

Textile Effects

Reflectance Curves/2

Reflectance Curve of a Green Color

0

0.1

0.2

0.3

0.4

0.5

0.6

400 500 600 700

Wavelength [nm]

Re

fle

cta

nc

e f

ac

tor

be

ta

absorbed light

reflected light

Reflectance curve of a blue shade

0

0.1

0.2

0.3

0.4

0.5

0.6

400 500 600 700

Wavelength [nm]

Re

fle

cta

nc

e fa

cto

r b

eta

reflected light

absorbed light

Textile Effects

Commission International de l‘Éclairage (CIE)

The CIE has defined several standard illuminants:

D65 = Average daylight (6500 K)

A = Tungsten (incandescent) light (2854 K)

But also fluorescent lamps like:

F2 = Cool White Fluorescent CWF (4200 K)

F11 = Fluorescent light Philips TL84 (4000K)

The illuminants are defined by its color temperature

and the relative spectral energy distribution.

Textile Effects

CIE Standard Illuminant D65 Daylight (6500 K)

0

50

100

150

350 400 450 500 550 600 650 700 750

Wavelength in nm

Re

la

tive

sp

ec

tra

l e

ne

rg

y d

istrib

utio

n

Textile Effects

CIE Standard Illuminant A Incandescent light (2854 K)

0

50

100

150

200

250

350 400 450 500 550 600 650 700 750

Wavelength in nm

Relative spectral energy distribution

Textile Effects

CIE Illuminant F2 Cool White Fluorescent (4200 K)

0

10

20

30

40

50

350 400 450 500 550 600 650 700 750

Wavelength in nm


Textile Effects

CIE Illuminant F11 Fluorescent light Philips TL84 (4000 K)

0

20

40

60

80

100

350 400 450 500 550 600 650 700 750

Wavelength in nm

Re

lative

sp

ectra

l en

ergy d

istrib

utio

n

Textile Effects

Human Eye

Cross section of the human

eye

Cross section of the retina

Textile Effects

Human Eye/2

In the retina there are two different types of optical sensors:

Rods for light/dark sensation

Cones for color sensation

Cones are sensitive to red or green or blue. CIE has defined

the sensitivity of the cones as standard observers for:

10° (large field)

2° (small field)

Textile Effects

CIE Standard Observer 10°

0.0

0.5

1.0

1.5

2.0

2.5

350 450 550 650 750

Wavelength in nm

Tristim

ulu

s va

lu

es illu

min

ant E

_

x_

y

_

z

Textile Effects

The color vision process

textile sample

CIE Standard Illuminant D65

(Daylight)

0

50

100

150

350 400 450 500 550 600 650 700 750

Wavelength in nm

Re

lative sp

ec

tral e

ne

rgy d

istribu

tion

light source

Reflectance curce of a yellow

shade

0

0.2

0.4

0.6

0.8

1

400 500 600 700

Wavelength [nm]

Re

fle

cta

nc

e fa

cto

r b

eta

absorbed light

reflected light

Reflectance curve

eye sensors

CIE Standard Observer Red

0.0

0.5

1.0

1.5

380 430 480 530 580 630 680 730

Wavelength in nm

Tristim

ulu

s va

lu

es

_

x

CIE Standard Observer Green

0.0

0.5

1.0

1.5

380 430 480 530 580 630 680 730

Wavelength in nm

Tristim

ulu

s va

lu

es

_

y

CIE Standard Observer Blue

0.0

0.5

1.0

1.5

2.0

2.5

380 430 480 530 580 630 680 730

Wavelength in nm

Tristim

ulu

s va

lu

es

_

z

Textile Effects

The color vision process/2

3 color signals from a Yellow color

Red Signal of a Yellow Color

0

20

40

60

80

100

400 500 600 700

Wavelength in nm

Tristim

ulu

s va

lu

es D

65

/1

0

X

Green Signal of a Yellow Color

0

20

40

60

80

100

400 500 600 700

Wavelength in nm

Tristim

ulu

s va

lu

es D

65

/1

0

Y

Blue Signal of a Yellow Color

0

20

40

60

80

100

400 500 600 700

Wavelength in nm

Tristim

ulu

s va

lu

es D

65

/1

0

Z

Textile Effects

CIE Color Coordinates

Calculation of CIE

Tristimulus Values

X k S x _

400

700

Y k S y _

400

700

Z k S z _

400

700

Calculation of CIE

chromaticity coordiantes

xX

X Y Z

yY

X Y Z

zZ

X Y Z

S = illuminant e.g D65

x,y,z = CIE standard observer

= reflectance factor

k = normalization factor

The sum of x+y+z

is always 1.

Textile Effects

CIE 1931 chromaticity diagram

Textile Effects

Let‘s talk about Color difference and tolerances

Textile Effects

MacAdam Ellipses

The MacAdam ellipses

define the visible color

difference perceptibilty

within the CIE diagram.

They show, that the CIE

x,y,Y color space is not

equidistant to our

visual perception.

Textile Effects

Uniform Color Spaces

To improve the non-uniformity of the CIE 1964 color space,

several transformation from x,y,Y color space to systems with

better uniformity have been developed, e.g. :

Hunter : L, a, b

Adams-Nickerson : ANLAB

CIE 1976 : L*, a*, b*

Textile Effects

CIE 1976 Color Space

Lightness L*

Red-Green axis a*

Yellow-Blue axis b*

Chroma C*ab

Hue hab

L Y* * 116 16

a X Y* ( * *) 500

b Y Z* ( * *) 200

)*

*arctan(

a

bhab

2/122 )**(* baCab

Textile Effects

Calculation of CIELab difference

Lightness

difference:

dL* = L*sample - L*standard

+ = lighter - = darker

Red - Green difference :

Yellow-Blue difference:

Total colour difference::

approximate perceptibility = 0.2 - 0.5

da* = a*sample - a*standard

+ = redder - = greener

db* = b*sample - b*standard

+ = yellower - = bluer

2/1222 )*)(*)(*)((* dbdadLdEab

Textile Effects

Calculation of CIELCH difference

Lightness difference :

dL* = L*sample - L*standard

+ = lighter - = darker

Chroma difference :

Hue difference :

dCab

* = Cab

*sample - Cab

*standard

+ = brighter - = duller

Red + = yellower - = bluer

Yellow + = greener - = redder

Green + = bluer - = yellower

Blue + = redder - = greener

The interpretation is

depending on the hue,

e.g. :

2/122 )*)(*)(*((* dCdLdEdH ab

Textile Effects

Production Control - Color tolerances

The CIE-Lab color space is, like the CIE-x,y,Y color

space, visually not equidistant. The uniformity has

been improved, but is not yet perfect. Therefore

tolerances have to be defined for each color.

Also the different visual sensitivity of lightness-

chroma- or hue-differences has to be considered.

To define tolerance limits, sufficient and reliable

visual jugements are necessary.

Around each standard color up to 50 trials should be

distributed evenly and a minimum of 20 to 30 colorists

should assess the differences - this means a total of

1000 visual assessments for each colour.

Textile Effects

Production Control - Pass/fail formulas

To avoid the huge effort of defining tolerances for each color, the CIELab

color space has been modified by weighting the lightness- chroma- and hue

difference in the formula, using large data sets from the industry.

Some of this modified formulas are:

JPC79 (J.P.Coats)

CMC (l:c) (Colour Measurement Committee, UK)

BFD (l:c) (Bradford university, UK) (l:c is the ratio of lightness and chroma, recommended is 2:1)

M&S89 (Marks & Spencer)

Datacolor

ISO recommends the CMC (l:c) formula for small color differences (ISO/DP

105-J01).The CMC (l:c) formula has some disadvantages in the blue range

of the color space. This has been improved with the BDF(l:c) formula, but

there is not enough experience to tell if BDF is generally better than CMC.

Textile Effects

CIE-Lab Tolerancing

CIE-Lab defines a cubic

color space, which does

not always correlate with

our visual perception

Textile Effects

CIE-LCH Tolerancing

CIE-LCH coordinates define

a cylindrical color space.

The correlation with our

visual perception is much

better.

Textile Effects

CMC Tolerancing

CMC uses tolerance

ellipsoids, which have

different shapes within

the color space.

They have been adapted

to visual color perception

Textile Effects

Let‘s talk about Metamerism and Color Constancy

Textile Effects

Metamerism

Same colors under

daylight illumination

Different colors under

shop illumination

Textile Effects

Metameric colors under D65

Brown 1 Brown 2

Textile Effects

Metameric colors under TL84

Brown 1 Brown 2

Textile Effects

Metamerism

If a pair of samples looks identical under a particular illuminant, but

different under another light source, the samples are described as

metameric.

They have different reflectance curves and produce different sets of

color co-ordinates under different light sources.

In colorimetry, metamerism is defined using a metamerism index.

Textile Effects

Reflectance Curves of metameric Colors

0

0.2

0.4

0.6

0.8

400 450 500 550 600 650 700

Wavelength [nm]

Re

fle

cta

nc

e f

ac

tor

be

ta

Brown No. 1

Brown No. 2

Textile Effects

Metamerism Index

lluminant Co-ordinates Brown 1 Brown 2

D65/10 L* 35.1I 34.4

a* 5.8 4.3

b* 10.0 8.8

CIELab difference dE Standard 2.0

A/10 L* 51.9 52.0

a* 7.8 15.8

b* 7.0 5.5

Metamerism Index dE Standard 6.5

TL84/10 L* 51.6 50.2

a* 9.0 15.0

b* 4.0 2.9

Metamerism Index dE Standard 10.1

Textile Effects

Color Constancy

Same colors

under daylight

illumination

Same colors under

incandescent

lamp, but different

from daylight

Textile Effects

Color Inconstancy of a green color

Green color under

illuminant D65

Beige color under

illuminant A

Textile Effects

Color Constancy

If one sample changes color appearance when it is illuminated using a different light source, we talk about good or inadequate color constancy of the sample.

The different spectral energy distribution of the light source in combination with the reflectance curve of the sample results in a change in color appearance.

In colorimetry, color constancy is defîned by a color inconstancy index.

Textile Effects

Color Constancy/2

Reflectance curve of a green shade

0

0.2

0.4

0.6

0.8

1

400 500 600 700

Wavelength [nm]

Re

fle

cta

nc

e fa

cto

r b

eta

Textile Effects

CIE Standard Illuminant D65 Daylight (6500 K)

0

50

100

150

350 400 450 500 550 600 650 700 750

Wavelength in nm

Re

la

tive

sp

ec

tra

l e

ne

rg

y d

istrib

utio

n

Textile Effects

CIE Standard Illuminant A Incandescent light (2854 K)

0

50

100

150

200

250

350 400 450 500 550 600 650 700 750

Wavelength in nm


Textile Effects

Color Constancy Index

Reflectance data

Color Co-ordinates

reference illuminant

Lr, a

r, b

r

Color Co-ordinates

test illuminant

Lt, a

t, b

t

Chromatic

adaptation

Color Co-ordinates

chromatic adapted

Lc, a

c, b

c

Inconstancy

Index dE

Color

difference

Textile Effects

Color Constancy Index/2

Color

Coordinates

D65/10

reference

illuminant

Color

Coordinates

A/10

test illuminant

Color

Coordinates

Chromatic

adapted

L*r 56.6 L*t 56.8 L*c 56.6

a*r -4.6 a*t 3.5 a*c 2.3

b*r 9.3 b*t 7.4 b*c 6.7

Difference

dL* 0.0

da* 6.9

db* -2.6

Inconstancy Index

dE 7.3

Textile Effects

Main source of metamerism problems

Designers chose shades from substrates different from intended textile, colored

with very different trichromies

Examples :

From a PANTONE color selector, in which case the color has been obtained by printing on

paper, with a trichromy of:

=> greenish yellow („Yellow“)

=> pinkish red („Magenta“)

=> turquoise („ Cyan“)

This is much different from a typical textile trichromy , usually based upon:

=> golden yellow

=> bluish red

=> reddish or neutral blue or navy

Other supports of designer inspiration: plastic, wood, foliage, photos ...

(between standard sample and actual dyehouse dyeing)

Textile Effects

Designers chose shades from substrates different from intended textile, colored

with very different trichromies

This „original“may have good- or poor color constancy.

Along the communication line, the shade samples are matched as non-

metameric compared to this original sample .

The prefered, often most robust-, fast- and economical trichromies used in

dyehouses do not always allow a non-metameric shade compared to such

standards



Textile Effects

Metamery caused by the initial choice by designers of a colored original which

coloration is not based on a textile dyers logic

is causing problems all along the textile logistical chain

=> technically- or economically sub-optimal dyeing recipes

=> waste of time and high cost



Textile Effects

Let‘s talk about Spectrophotometer settings and sample preparation

Textile Effects

Spectrophotometer settings and sample preparation

To guarantee exact color measurements, the settings of the

spectrophotometer and the preparation of the samples have to

be defined clearly.

The following parameters can have a large influence on the

measurement:

• Specular component included or excluded

• UV component included, calibrated or excluded

• Aperture size

• Number of sample layers

• Number of readings per sample

• Conditioning of the sample

Textile Effects

Influence of specular component

0

0.1

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0.3

0.4

0.5

0.6

400 450 500 550 600 650 700

Wavelength [nm]

Re

fle

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Blue 24 specular included

Blue 24 specular excluded

Substrate: Acetate Woven Satin

0

0.1

0.2

0.3

0.4

0.5

0.6

400 450 500 550 600 650 700

Wavelength [nm]

Re

fle

cta

nc

e f

ac

tor

be

ta

Blue 24.2 specular excluded

Blue 24.2 specular included

Substrate: Acetate Woven Satin

Textile Effects

Influence of specular component/2

Standard: Blue 24 specular excluded ---- Illuminant/Observer ----

Sample: Blue 24 specular included D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.62 0.63 0.64

Standard: Blue 24.2 specular excluded ---- Illuminant/Observer ----

Sample: Blue 24.2 specular included D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.63 0.64 0.64

Textile Effects



Sample: Blue 24.2 specular excluded D65/10 CWF/10 A/10

CMC(2:1) dE CMC 1.79 1.87 1.84

Standard: Blue 24 specular included ---- Illuminant/Observer ----


CMC(2:1) dE CMC 1.79 1.87 1.84

Textile Effects




CMC(2:1) dE CMC 2.43 2.53 2.51

Textile Effects

Influence of UV component

0

0.25

0.5

0.75

1

1.25

1.5

380 430 480 530 580 630 680

Wavelength [nm]

Re

fle

cta

nc

e/E

mis

sio

n f

ac

tor

Blue 2BR with full UV

Blue 2BR with UV calibrator

Blue 2BR with cutoff FL 400

Substrate: PES Jersey with FWA

0

0.2

0.4

0.6

0.8

1

1.2

380 430 480 530 580 630 680

Wavelength [nm]

Re

fle

cta

nc

e/E

mis

sio

n f

ac

tor

Red 4BS with full UV

Red 4BS with UV calibrator

Red 4BS with cutoff FL 400

Substrate: PES Jersey with FWA

Textile Effects

Influence of UV component/2

Standard: Blue 2BR with full UV ---- Illuminant/Observer ----

Sample: Blue 2BR with UV calibrator D65/10 CWF/10 A/10

CMC( 2:1) dE CMC 2.67 2.56 2.13

Standard: Blue 2BR with full UV ---- Illuminant/Observer ----

Sample: Blue 2BR with cutoff FL 400 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 11.50 10.56 8.46

Textile Effects

Influence of UV component/3

Standard: Red 4BS with full UV ---- Illuminant/Observer ----

Sample: Red 4BS with UV calibrator D65/10 CWF/10 A/10

CMC(2:1) dE CMC 1.93 2.33 2.17

Standard: Red 4BS with full UV ---- Illuminant/Observer ----

Sample: Red 4BS with cutoff FL 400 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 7.96 9.82 8.56

Textile Effects

Influence of sample layers

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

400 450 500 550 600 650 700

Wavelength [nm]

Re

fle

cta

nc

e f

ac

tor

be

ta

Yellow 1 layer / white

Yellow 1 layer / black

Yellow 2 layers / white

Yellow 2 layers / black





Substrate: CO knitwear

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

400 450 500 550 600 650 700

Wavelength [nm]

Re

fle

cta

nc

e f

ac

tor

be

ta

Blue 1 layer / white

Blue 1 layer / black

Blue 2 layers / white

Blue 2 layers / black

Blue 4 layers / white

Blue 4 layers / black

Substrate: PES Micro woven

Textile Effects

Influence of sample layers/2

Standard: Yellow CO knit 1 layer/white ---- Illuminant/Observer ----

Sample: Yellow CO knit 1 layer/black D65/10 CWF/10 A/10

CMC(2:1) dE CMC 4.91 4.91 5.17

Standard: Yellow CO knit 2 layers/white ---- Illuminant/Observer ----

Sample: Yellow CO knit 2 layers/black D65/10 CWF/10 A/10

CMC(2:1) dE CMC 1.47 1.29 1.52

Textile Effects




CMC(2:1) dE CMC 0.12 0.09 0.13



CMC(2:1) dE CMC 0.10 0.10 0.10

Textile Effects


Standard: Blue PES micro 1 layer/white ---- Illuminant/Observer ----

Sample: Blue PES micro 1 layer/black D65/10 CWF/10 A/10

CMC(2:1) dE CMC 1.10 1.11 0.97

Standard: Blue PES micro 2 layers/white ---- Illuminant/Observer ----

Sample: Blue PES micro 2 layers/black D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.06 0.05 0.06

Standard: Blue PES micro 4 layers/white ---- Illuminant/Observer ----

Sample: Blue PES micro 4 layers/black D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.04 0.04 0.03

Textile Effects

Influence of readings

Standard: Peach 1 reading/1 ---- Illuminant/Observer ----

Sample: Peach 1 reading/2 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.07 0.07 0.07

Standard: Peach 2 readings/1 ---- Illuminant/Observer ----

Sample: Peach 2 readings/2 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.04 0.04 0.04

Standard: Peach 3 readings/1 ---- Illuminant/Observer ----

Sample: Peach 3 readings/2 D65/10 CWF/10 A/10

CMC( 2:1) dE CMC 0.03 0.03 0.04

Textile Effects

Influence of readings/2

Standard: Red 1 reading/1 ---- Illuminant/Observer ----

Sample: Red 1 reading/2 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.05 0.05 0.05

Standard: Red 2 readings/1 ---- Illuminant/Observer ----

Sample: Red 2 readings/2 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.04 0.04 0.04

Standard: Red 3 readings/1 ---- Illuminant/Observer ----

Sample: Red 3 readings/2 D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.01 0.01 0.01

Textile Effects

Influence of light exposure (Photochromie)

Standard: Beige 1 ---- Illuminant/Observer ----

Sample: Beige 1 after 2h exposer D65/10 CWF/10 A/10

CMC(2:1) dE CMC 0.23 0.19 0.19



CMC( 2:1) dE CMC 0.25 0.20 0.20

Textile Effects

Influence of light exposure/2 (Photochromie)



CMC( 2:1) dE CMC 0.24 0.17 0.18


Sample: Beige 1 after 24h in the dark D65/10 CWF/10

A/10

CMC( 2:1) dE CMC 0.06 0.08 0.06

Textile Effects




CMC(2:1) dE CMC 0.09 0.08 0.07



CMC( 2:1) dE CMC 0.13 0.11 0.10

Textile Effects




CMC( 2:1) dE CMC 0.12 0.12 0.11


Sample: Beige 2 after 24h in the dark D65/10 CWF/10

A/10

CMC( 2:1) dE CMC 0.11 0.13 0.14

Documents

Let‘s talk about Colorimetric Basics · Colorimetric Basics . Textile Effects Electro-Magnetic Waves visible light . Textile Effects Different technics of color mixtures Subtractive