Auto Color Seminar JISL MK

8/7/2019 Auto Color Seminar JISL MK

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Colour and Textile Products

Color Measurement inPractice

Manish KapadiaChief Manager - CTP

Jay Instruments & Systems Pvt. Ltd.India


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Mechanism of color perception

Mechanism of color perception

How human eyes get tricked

How human eyes get tricked

Mismatches between colorinstrument measurements andvisual evaluation (how to chooseright instrument and method)

Mismatches between colorinstrument measurements andvisual evaluation (how to chooseright instrument and method)

Examples of use in variousindustries

Examples of use in variousindustries

Seminar program

contents


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The Instrument Systems Company today

Seven main business fields

ColourLight Display 3D TemperatureMedical

Konica Minolta Sensing, Inc.

Current Product Line

http://www.konicaminolta.com/instruments/
http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/http://www.konicaminolta.com/instruments/


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Applications & Instruments

Plastic / Auto

Cosmetics

Paint/Automotive

Ceramics

Coatings

Packaging

Food

Pharmaceuticals

BuildingMaterials

Textile

Color

Reflectanceandtransmittance

Spectrometers

Chromameters

Glossmeters

QC software: SpectraMagic NX

CCM software: Colibri, Jaypak

Paper


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Mechanism of colorperception Mechanism of colorperception

C l i bi i f 3C l i bi ti f 3


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What color tone?How bright? How vivid?

Light

Subdued

Vivid

Dark

Red

Red

Chroma

Hue

Lightness

3 characteristicsof color L C H

Color is a combination of 3Color is a combination of 3

elementselements

Color is a combination of 3Color is a combination of 3

elementselements


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Color perceptionColor perceptionColor perceptionColor perception

What is Light?

What is Reflected

light? What is the structure

of the Eye? Light

ObjectEye

Let's look at these three elements in order.


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Electromagnetic wave spectrum byElectromagnetic wave spectrum by

wavelengthwavelength

Electromagnetic wave spectrum byElectromagnetic wave spectrum by

wavelengthwavelengthLong

Short

Light is a very small partof the electromagnetic

spectrum.

The human eye can see onlyvisible light from a range of

380-780nm.


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If light falls on an objects,its way will be changed by

the object in different ways:

Incident

Specular

Transmission

Scattering

Absorption


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Spectral reflectance of

apple's red color

Why does anapple appear

red?

This curve isindependant from theilluminated light: it isonly the percentage ofreflected light to

illuminated light.


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For different samples (colors), the amount oflight absorbed or reflected at each wavelength

varies.

0

100

Reflectanc

e(%)

0

100

Reflectan

ce

(%)

WHITE BLUE


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Structure for seeing colorStructure for seeing colorStructure for seeing colorStructure for seeing color

Line ofsight

Lens

Cornea

RetinaFovea

centralis

Opticnerve

Blindspot

NoseBrainRight eye

The image isprojected onto

the eye's

retina.

Photoreceptor cellsin the retina

convert the light toelectrical signals.

Optic nervescarry the

signals to thebrain.

Information isrecognized by

the brain.

Photorecept

or cells

Retina structure andRetina structure and

Ret na structure ane na s ruc ure an


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Retina structure andRetina structure andoperationoperation

Ret na structure ane na s ruc ure anoperationoperation

Color informationColor information is perceived

by 3 kinds of cells called"cones"

Brightness informationBrightness information is

perceived by cells called "rods"

Ratio of cone types

L cones: Visible long-wavelength region (Red): 32

M cones: Visiblemedium-wavelength region (Green): 16

S cones:Visible short-wavelength region (Blue):1

LightApprox. 100 million rods

Approx. 7 million cones


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400 500 600 700

Structure for seeing colorStructure for seeing colorStructure for seeing colorStructure for seeing color

Interpretation: Red

Physics + physiology + psychology


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How human eyes get tricked How human eyes get tricked

illusion: white or black dots?


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Lightsource

Lightsource

Illuminationand viewing

direction

Illuminationand viewing

direction

ViewerViewer

MemoryMemory

Viewer's

condition

Viewer's

condition

Backgroun

d

Backgroun

d

The appearance of a color isaffected by a variety of conditions

Object sizeObject size


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1 Lightsource

Lightsource


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Sunlight

Fluores-cent

Incandes-cent

Sunny Rainy Morning

After-noon

EveningCloudy

Wavelength distributions of various lightWavelength distributions of various lighta

ve eng s r u ons o var ous gave eng s r u ons o var ous g


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Average daylight(CIE Illuminant D65)

Tungsten lamp(CIE Illuminant A)

Fluorescent lamp(CIE Illuminant

F11)

Wavelength distributions of various lightWavelength distributions of various lightsourcessources

ave eng s r u ons o var ous gave eng s r u ons o var ous gsourcessources

200

100

0

Wavelength (nm)

Light such as from the sun, tungsten lamps, fluorescent lamps, etc. which does notappear strongly colored and is a mixture of all wavelengths in the visible range is termed"white light".

Dining room Convenience store,supermarket, office,

factory

Natural light

Wavelength (nm) Wavelength (nm)

R l Lif E l


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Real-Life Example

Bring it

home

MeatMeat

CounterCounter


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Background

Background

2


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I ddi i li h


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Chroma contrast and Hue contrastChroma contrast and Hue contrast

In addition to lightnesscontrast ...

Reddishorange

Yellowishorange

Bright orange Subduedorange

Hue/Chroma ... also affect how a color appears.

Illuminatio

Illuminatio3


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n andviewingdirection

n andviewingdirection

3


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Samples whose colors appearSamples whose colors appear



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Glossy samples Metallic or

pearlpaints

Textured

samples andtextiles


different depending ondifferent depending on

illumination/illumination/viewingviewing directiondirection


different depending ondifferent depending on

illumination/illumination/viewingviewing directiondirection

Transparent and translucent samples


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RedDeepred

Metallicpaint

Lightsource

The same liquid in different containers


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Light

source

Deep

blueLight

source

Paleblue

The distance the light passes through the liquid (the optical path length)

changes.

q

Vi4


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ViewerViewer4


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The sensitivity of the eye is different for each person andh ith

The sensitivity of the eye is different for each person andchanges with age


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Yellowis

h red

Bright

red

Somewhat vivid

red

changes with agechanges with age

What is shown on the pictures?What is shown on the pictures?


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10 5 8

Viewer's

Viewer's5


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Even if the light source, background, viewingangle, and viewer are kept constant ...

conditioncondition5


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The person's physical or emotionalcondition can affect their response to

color


color


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color


color

Tired!Tired!

Memory

Memory6


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MemoryMemory


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It is easy to see the differenceIt is easy to see the difference


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The same or not???The same or not???

Real-Life ExampleThat would

But athome


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FURNITURE

SALE!

That wouldlook nice...

home...

Object size

Object size7


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Object sizeObjec s e

"Area effect" of color

If two areas are the samecolor, the larger area willtend to look brighter andmore vivid than the

smaller area.The color of a target-color

plate specified using asmall color sample will loodifferent than the color ofthe actual object.

There are two different standard observers defined byCIE


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CIE

10 Observer

Distance 30 cm

5cm

1cm

2 Observer

Viewingangle

Viewingangle

Viewer

Viewer


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LightsourceLight

sourceMemoryMemory

Viewer's

condition

Viewer's

condition

Backgroun

d

Backgroun

d

Object sizeObject size

E l f i l QC t l


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OK

NGExample of wrong visual QC control

Visual vs. instrumental color assessment


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Element Influence on the color assessment

visual instrumental

Area not defined measuring spot

Light source defined when using a light cabinet norm light sources

Object angle of incident and reflected light measuring geometry

Sensing eye (receptors) sensor (norm observer)

Processing individual (experience, sensitivity) mathematical

Result verbal (individual); no memory numerical (objectiv), storable

only qualitativ and very individual qualitativ and quantitativ

Use color cabinet if visual control is stillUse color cabinet if visual control is still

requiredrequired

Use color cabinet if visual control is stillUse color cabinet if visual control is still

requiredrequired


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requiredrequiredrequiredrequired

The equipment shown at left iscommonly called a light box orcolor cabinet, and is used forvisual evaluation under anartificial light source.

The samples for comparison areplaced in the light box, and the

observer stands in front of thelight box to perform visualevaluation while switching

between the light-box lightsources (Illuminant D65,fluorescent, Illuminant A, etc.)

Since the light box uses artificiallight sources, visual evaluationcan be performed under a stablelight source.

Effects of digital colorEffects of digital colorspecificationspecification



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specificationspecificationspecificationspecification When colors can be specified using digitaldata, there is no need to create numerous target

color plates and send them to each supplier.

Target color plate

Company A

Company B

Company C




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specificationspecificationspecificationspecificationPlus, there is no need to store large quantities of targetcolor plates, and no need to maintain a place to store

such plates.

But ...


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Visualevaluation

Color-measuringinstrument

Color measurement resultsmay not match visual

evaluation!

But ...


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Mismatches between colorinstrument measurements andvisual evaluation

Mismatches between colorinstrument measurements andvisual evaluation

Even for the same E*ab, the difference may not be

For example:


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ynoticeable between vivid colors but is clearly seen for

pale colors

I can'tsee anydifferenc

e!

E*ab=1

Thecolors

aredifferent

!

E*ab=1

When indoor visual evaluation resultsand E*ab are compared:


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Even though the colors appear different,

the E*ab value is small!

The colorsare

different!

E*ab=0.5

Fluorescentlamp

When color cards are used as standards and color-matched paint or plastic samples are compared:


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The colorsmatch!

E*ab=5

PantoneDIC

Even though the colors appear well-matched,the E*ab value is large!

With metallic or pearl paints:


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The colorsare a bitdifferent.

Even though the color is a bit different visually,

the

E*ab value is small

E*ab=0.5

S


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So ...

Color-measuring

instruments aren't goodfor anything!

But is thisreally true?

Common misconception #1Common misconception #1



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Metamerism

Under certainspecific conditions

the colors match.

When indoor visual evaluation resultsand E*ab are compared:


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Even though the colors appear different,

the E*ab value is small!

The colorsare

different!

E*ab=0.5

Fluorescentlamp

But if visual evaluation is done outdoors:


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Hey! The colors look the same!

The colorsmatch.

Sunlight

E*ab=0.5


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Why does this type

of phenomenonoccur?

Th t l fl t

To make an orange color:To make an orange color:



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Orangecolor

Yellowpigment

Redpigment

The spectral reflectance curvebecomes rough when the

reflectance curve of yellow and

the reflectance curve of red arecombined.




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Orange pigment

The spectralreflectance curve

becomes a smoothcurve.

Orangecolor




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VS

Orange

color

Orange pigment

Yellow pigment

Redpigment




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Orange pigment

Yellow pigment

Redpigment

When different pigments are used to match colors, the spectral reflectancecurves become greatly different, and in such cases metamerism occurs.

Even for car interior materials


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Goodparts

The parts looked

good indoors, but ...

Inside the car under

outdoorillumination ...

Even though the colors appear different

When samples may bemetameric:


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Even though the colors appear different,the E*ab value is small!

The colorsare

different!

E*ab=0.

5

Fluorescentlamp

Under afluorescent

illuminant, E*ab=3

Measure colors with aspectrophotometer, and lookat the E*ab under the lightsources that will be used for

visual evaluation.

E* b b d d i t f li ht

WhenWhen E*ab is measured using aE*ab is measured using aspectrophotometerspectrophotometer::

WhenWhen E*ab is measured using aE*ab is measured using aspectrophotometerspectrophotometer::


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E*ab can be measured under a variety of light source

Thecolors

aredifferent

!

E*ab=3

Thecolorsmatch!

E*ab=0.5

Fluorescentlamp

Sunlight

Tristimulus type Spectral type


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Spectral sensor

Measures sample

reflectanceateach wavelengthusing a 10nm-pitch

spectral sensor

How a spectrophotometer determines colorimetricHow a spectrophotometer determines colorimetricvaluesvalues

How a spectrophotometer determines colorimetricHow a spectrophotometer determines colorimetricvaluesvalues

Instrument already Instrument Instrument already


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Spectral reflectanceof sample

Illuminant spectraldistribution

F6F8

F10

A

D65

C

Spectral sensitivitycorresponding to

human eye

Tristimulus values XYZ

Color spaces L*a*b* L*ChYxyMunsell etc.

Calculation

contains this data measures thisy

contains this data

Calculation

Be careful with mass-productionBe care u w t mass-pro uct onprototypesprototypes

e care u w mass-pro uc on-

prototypesprototypes

Since the pigments for each part are different,metamerism may occur


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metamerism may occur

Color sample

Particularly for colors such as grays or ivories, since they

can be matched using a variety of pigments, metamerismoften occurs.

CColor quantificationolor quantification & Color& ColorSpacesSpaces

CColor quantificationolor quantification & Color& ColorSpacesSpaces


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CIE: Commission International de l'Eclairage

Munsell color notation

XYZ (Yxy) color space

L*a*b* color system

1905

1931

1976

Hunter Lab color space1948

Color solid (Munsell system)Color solid (Munsell system)


The Munsell system is a color system approved by the Optical


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The Munsell system is a color system approved by the Optical

Society of America (OSA) based on a color system initiallydeveloped in 1905 by A. H. Munsell, an artist and art teacher,with scales modified by OSA members.

H (Hue) = 2.5R

V (Value) = 4


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Munsell color soli

2.5R

5R

10RP

5B

10B

5PB

Chroma

V

alue

Hue

V (Value) = 4

C (Chroma)= 12

Indicates

lightness

Hue: 10 directionsRed, Yellow Red, Yellow, Green

Yellow, Green, Blue Green,


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Value: 10

steps10 steps of value(lightness) from black towhiteChroma: 10 steps

Oil paints of the time had a maximum

chroma of 10. Today's pigments can goup to 14 to 18.

e o , G ee , ue G ee ,Blue, Purple Blue, Purple, RedPurple



H th M ll t i t it bl f t l f


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However, the Munsell system is not suitable for actual use forcolor control, because there are an infinite number of colors for

which the Munsell system does not have color chips.

It is said that the human eye can recognizeabout 1 million to 10 million different colors!

So various continuous color spaces weredeveloped to enable quantification of allcolors.


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L*C*h color

space

XYZ colordiagram (1931)

Hunter Lab colorspace (1948)

UCS colordiagram (1976)

L*u*v* colorspace (1976)

L*a*b* colorspace (1976)

a co orspacespace

spacespace

L*

100=White


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L*

a*

0=Black

+:Red- : Green

+ : Yellow

- : Blueb*

L*a*b* colorL*a*b* colorspacespace

L*a*b* colorL*a*b* colorspacespace

ll


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100=White

0=Black

+ = Yellow

+=Red

- = Blue

- = Green

b*

a*L*

L*a*b* color spaceL*a*b* color space animationanimation

L*a*b* color spaceL*a*b* color space animationanimation


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E:\Dokumenty\Imprezy\2009\2009-09-16 Brn

L*a*b*

L*C*h Color SystemL*C*h Color System


L*C*h


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L a b

GreenRed

Yellow

Blue

Hue

C*: Chroma

a* 50.00b* 20.00

C* 53.85h 21.80

C* expresses the chroma.

As the C* value increases, thecolor point moves outward fromthe center of the plot, indicatingthat the color is becoming morevivid. Smaller values of C*indicate colors that are subdued.

L*a*b*

Yellow

L*C*h ColorL*C*h ColorSystemSystem

L*C*h ColorL*C*h ColorSystemSystem L*C*h

h expresses the hueangle. The angle is 0at 90


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GreenRed

Blue

Hue

a* 50.00b* 20.00

C* 53.85

h 21.80

the +a* axis (red), andincreases

counterclockwise aroundthe circle to indicate theposition of the color.

h: Hueangle

180

270

0

Yellow

L*a*b* L*C*h

L*C*h equations:

( ) ( )22 *** bC +


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Green

Red

Blue

Hue

h: Hueangle

a* 50.00b* 20.00

C* 53.85

h 21.80

( ) ( )*** baC +=

=

*

*tan

1

a

bh

C*: Chroma

With a* and b*, it's difficult toi di l j d h h l i




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a* 50.00b* 20.00

C* 53.85

h 21.80

In addition, it also solvesthe following problem of L*a*b*

C*:Chroma

h: Hue angle

immediately judge what the color is

like, but Chroma C* and Hue angle hare directly related to humanperception, making it a color

notation that is easier to judge.

Differences between L*a*b* and L*C*hDifferences between L*a*b* and L*C*hcolor notationscolor notations



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Which color looks redder?

Differences between L*a*b* and L*C*hD erences etween L*a* * an L*C*

color notationscolor notations

e

rences e ween a an

color notationscolor notations



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L* 56.47

a* 43.08

b* 42.07

C* 60.21

h 44.32

L* 41.85

a* 40.30

b* 18.26

C* 44.25

h 24.38

+b*


Differences between L*a*b* and L*C*h colorDifferences between L*a*b* and L*C*h colornotationsnotations

Differences between L*a*b* and L*C*h colorDifferences between L*a*b* and L*C*h color

notationsnotations

L* 41 85


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+a*

+b*

Chroma

L* 56.47

a* 43.08

b* 42.07

C* 60.21

h 44.32

L* 41.85

a* 40.30

b* 18.26

C* 44.25

h 24.38

b*


Differences between L*a*b* and L*C*hDifferences between L*a*b* and L*C*hcolor notationscolor notations L*a*b*:a* Less reddish


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a*

Standar

d

Sample

Even thoughsample is

more reddish,the a* value

is lower.

When comparing 2 colors

L*C*hC* Less vivid

h More

reddish

Chroma

b* Less

yellowishStandard

Sample

Expressing color differencesExpressing color differences

Expressing color differencesExpressing color differences

Measure the L*a*b* values of


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both the target and sample.

Difference in brightness isexpressed as L*.

Color difference is expressedas E*ab, which is calculatedfrom L*, a*, and b*.

A: Color of target

B: Color ofmeasured sample

L* = 50.0 L*1= 55.0

Standard

Sample

Calculating color differenceCalculating color difference E*abE*ab

Calculating color differenceCalculating color difference E*abE*ab


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a* = +25.0

b* = + 5.0

a*1 =+

20.0

b*1 =+

5.0 E*ab= L*1 L*

2 + a*1 a*2 +

b*1 b*2

= 55.0 50.0 2 + 20.0 25.0 2 + 5.0 5.0 2

= 5.0 2 + -5.0 2 + 0.0 2

= 25.0 + 25.0 + 0.0

= 50.0

Color difference which considers both

lightness difference and hue differenceequally




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Color differences E*ab or a*b* do

not match visualevaluation

Even for the same E*ab, the difference may not benoticeable between vivid colors but is clearly seen for

pale colors


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I can't

see anydifferenc

e!

E*ab=1

Thecolors

aredifferent

!

E*ab=1


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Why does this type

of phenomenonoccur?

White ellipses indicatecolor discrimination

ability of human eyes

Eyes are more sensitiveto hue changes than to

chroma changes

Differences in difference discrimination between human eyes andDifferences in difference discrimination between human eyes and

E*abE*ab

Differences in difference discrimination between human eyes andDifferences in difference discrimination between human eyes and

E*abE*ab


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Hue

Chroma

Chroma

Eyes are more sensitive

to changes at lowchroma than at high

chroma

Looks like samecolorWith E*ab

All 3 colors

Sample

Problems withProblems with E*abE*ab



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All 3 colors

pass

Looks likedifferent color

Looks like samecolor

Standard

SampleSample

E*ab

=

E*ab

=

Let's make the tolerance smalle



With E*ab

the tolerancebecomes too

small.


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E*ab

=

E*ab

=

If we make thecolor difference

tolerancesmaller ...

Then, if we try using a*b* to limit the shift in

h hi h b




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hue which seems to be a

problem,

since it doesn't match thediscrimination of the human eye,

there is still some shift from visualevaluation.

a*

b*

Differences in difference discriminationDifferences in difference discriminationbetween human eyes andbetween human eyes and E*abE*ab

Differences in difference discriminationDifferences in difference discriminationbetween human eyes andbetween human eyes and E*abE*ab


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The solution to theseproblems with E*ab is

CIE2000 ( E00)

3-dimensional ellipses withlightness L*,Chroma C*, and

hue h* as the axes.

... varying in

Compared to L*a*b* color difference E*ab, color discrimination ellipsesare:

Four differences in difference discrimination between human eyes and the L*a*b* colorFour differences in difference discrimination between human eyes and the L*a*b* colorspacespace

Four differences in difference discrimination between human eyes and the L*a*b* colorFour differences in difference discrimination between human eyes and the L*a*b* color

spacespace


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... larger aschromaticityincreases.

... tilted indirection inblue area.

y gwidth according

to hue.

... different insize according

to lightness.

CIE2000 solves all four of thesedifferences.

E00 =

E00 (CIE2000) color-difference equationE00 (CIE2000) color-difference equation

E00 (CIE2000) color-difference equationE00 (CIE2000) color-difference equation


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For low chroma of C*=1

SL=1 SC=1.13 SH=1.06

For high chroma of C*=50

SL=1.00, SC=5.51,SH=2.99

SL= 1 + ((0.015(L-50)

/ (20+(L-50)

) /

)

SC= 1 + 0.045 C

SH= 1 + 0.015 C T

anges n o erance e pseanges n o erance e pse

sizesize

sizesize100=White

If chromaticity is high (ex.: C*=50):SL=1.00, SC=5.51, SH=2.99Ellipse

is large


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b*

0=Black

+: Yellow

-: Blue

Origin

-: Green

a*

+: Red

C*: Chroma

H*: HueIf chromaticity is low (ex.: C*=1):SL=1.00, SC=1.13, SH=1.06

is large

Ellipse

is small




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Color differences

E*ab or a*b* do not match visualevaluation

This is not a misconception.This is actually true. But ...

... with CIE2000 ( E00), color evaluationand management correspond to visual

evaluation.




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Color comparison ofdifferent materials

Points for selecting the

appropriate color-measuringinstrument

When color cards are used as standards andcolor-matched paint or plastic samples arecompared:

Even though the colors appear well-matched,


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The colorsmatch!

E*ab=5

PantoneDIC

g pp

the E*ab value is large!


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Why does this type

of phenomenonoccur?

There are 2 causes:


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1. Differences inmaterials

Metamerism2. Differences in surfaceconditions

There are 2 causes:

1. Differences in materials Metamerism1. Differences in materials Metamerism

1. Differences in materials Metamerism1. Differences in materials Metamerism


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PantoneDIC

Painted plates

Plastic

Printing ink

Paint

Since the various coloring agents are different,

metamerism occurs

Coloring

compounds

Matte

2. Differences in surface2. Differences in surfaceconditionsconditions

2. Differences in surface2. Differences in surfaceconditionsconditions


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PantoneDIC Painted plates

Plastic

Semi-gloss

(No gloss)

Glossy

When performing visual evaluation of objects with different gloss conditions, be

sure to view the objects at an angle at which the reflection of the light sourcedoes not enter the eyes.

Light source and viewingLight source and viewingangleangle

Light source and viewingL g t source an v ew ng

angleangle


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Normally, viewing is notperformed like this.

Specularlyreflected

light

Diffusely

reflected light

Light that is reflected from the surface of an object at the equal butopposite angle to the angle from which the object was illuminated iscalled "specularly reflected light". Since this is a reflection of the

Specularly reflected lightSpecularly reflected light

Specularly reflected lightSpecularly reflected light


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p y g

light source itself, the color of this light is the color of the lightsource.

Measureme

nt subject

Light that is absorbed or dispersed by the colorants in ameasurement subject and reflected in a variety of directions iscalled "diffusely reflected light". The color of this light is the color

Diffusely reflected lightDiffusely reflected light

Diffusely reflected lightDiffusely reflected light


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called diffusely reflected light . The color of this light is the color

of the measurement subject.

Measureme

nt subject

Viewing should bedone from a

position at whicha reflected image

Light source and viewing angleLight source and viewing angle

Light source and viewing angleLight source and viewing angle


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a reflected image

of the light sourceis not seen.

View Angle

Optical systems that can provideOptical systems that can providecorrelation with visual evaluationcorrelation with visual evaluation

Optical systems that can provideOptical systems that can providecorrelation with visual evaluationcorrelation with visual evaluation


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Diffuse

illuminationmethod

Single-angle

illuminationmethod

Diffuse illumination methodDiffuse illumination method

Diffuse illumination methodDiffuse illumination method

If the surface gloss of the colorstandard and sample are different


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SCI SCE

Specular Component Included Specular Component Excluded

standard and sample are different,SCE (which does not include specularreflection of the light source) moreclosely matches visual evaluation.

Difference between SCI and SCEDifference between SCI and SCE

Difference between SCI and SCEDifference between SCI and SCEFor two blocks of the same material (plastic), if we use sandpaper to roughup the surface...

The color


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changed!!

It becomeswhitish.

No gloss Glossy Color difference

SCE can detect differences inSCE can detect differences inglossgloss

SCE can detect differences inSCE can detect differences inglossgloss


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SCI L* 43.33 43.09 L* -0.24

a* -1.07 -1.03 a* 0.04

b* -42.39 -42.58 b* -0.29

E*ab 0.31SCE L* 42.93 36.64 L* -6.29

a* -1.13 -1.01 a* 0.12

b* -42.53 -48.48 b* -5.95

E*ab 8.66




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Use SCE, which does not include specularly reflectedlight

However, for surfaces with rough textures, 45illumination/0 viewing geometry provides the closes

correlation with visual evaluation.

Color comparison ofdifferent materials

International standards for gloss

Specular Gloss


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GM-268

g

ISO 2813 ISO 7668 JIS Z 8741 ASTM D 523

ASTM D 2457 DIN 67 530 BS 3900 BS6161(Part12)

Glossmeter

GlossGloss

ishigh.

Glossis low.


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Low gloss High gloss

Frosted glass, chalk, matte paperAutomobile interiors

Glass, polished metal surfaces

Measurement PrincipleThe Glossmeter GM-268 can measure gloss at 3 angles.

20

Photo-

20GM-268


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Subject

85

60

Photo-

sensor

85

Photo-

sensor

Photo-sensor

60

GM 268

Specular Gloss MeasurementMethodsMeasurement

method60 speculargloss

20 speculargloss

85 speculargloss


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Symbol Gs(60) Gs(20) Gs(85)Application Plastic, paint,

porcelainenamel,anodized

aluminumcoatings, etc.

Plastic, paint,porcelainenamel,anodized


Paint,porcelainenamel,anodized


Applicablerange

Used whenGs(60) > 70

Used whenGs(60)


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GM-268

8520 60

Bottom view of GM-268




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For metallic and pearl paints,measurement values do not

match visual evaluation

Metallic paintsMetallic paints

Metallic paintsMetallic paints


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Highlight angle25

Shade angle

75

Reflectionfrom metalflakes(bright)

Absorption/dispersion by

colorants (creatingcolor)

Multiangle Spectrophotometer CM-Multiangle Spectrophotometer CM-512m3512m3

Multiangle Spectrophotometer CM-Multiangle Spectrophotometer CM-512m3512m3

ViewingViewing2525

IlluminationIllumination


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Let's measure colors witha multiangle

spectrophotometer

4545

7575

IlluminationIllumination

If plates painted with the same metallic paint but differentorientations of the metal flakes in the paint are measuredusing a diffuse-illumination instrument and a multiangle-illumination instrument:


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Luster material(metal flakes)

Same paintStandard Sample

Diffuse-illumination type

CR-400 CM-700d

Multi-angle illumination type

CM-512m3

SensorE*ab 0.3

CR-400 CM-700d

Sensor

Diffuse-illuminationDiffuse-illuminationtypetype

Diffuse-illuminationDiffuse-illuminationtypetype


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Light

source

For diffuse illumination, since the light illuminating the sample is reflectedmultiple times within the integrating sphere and averaged, even if theorientation of the metal flakes is different, there is no difference in themeasurement values.

Standard Sample

Light

source

E*ab 2.0

CM-512m3

Multiangle illumination typeMultiangle illumination type

Multiangle illumination typeMultiangle illumination type


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E*ab 3.3

E*ab 4.5

25

45

75

25

45

75

On the other hand, with multiangle illumination, thedifferences in appearance at each angle can be measured.

Lightsource

Sensor

Standard Sample

Lightsource

Lightsource

Lightsource

Lightsource

Lightsource

Sensor




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For metallic and pearl paints,measurement values do not

match visual evaluation

Take measurements with amultiangle illumination type

instrument.

Expressing color of translucentExpressing color of translucentplasticsplastics

Expressing color of translucentExpressing color of translucentplasticsplastics


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How should the color oftranslucent plastics be expressed?

Haze value and L*a*b* can beused to express the color of

translucent plastics numerically.

Color-measuringX


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By using the color-measuring instrumentappropriate for the sample,

and using CIE2000 color-difference valuesand L*C*h colorimetric values,

color measurement results corresponding well

with visual evaluation can be performed!

instruments aren't goodfor anything!X


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How to set

tolerances(Quality Control

limits)

How should I settolerances?


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Target-color plates Tolerance values

L* = +0.5, -0.5 ? a* = +0.5, -0.5 ?

b* = +0.5, -0.5 ? E*ab = +1.0, -1.0

Upperlimit

Targetcolor

Lowerlimit

How should I set tolerances?

When setting tolerances, pay attention to

the following:

1 Adj t th t l di t h


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1. Adjust the tolerance ranges according to hownoticeable the part is, whether the part isadjacent to another part, part manufacturingconditions, etc.

2. Choose the appropriate color space according tothe material being measured.

For example ...


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Are these

two colors

the same?

They look the same when they're separated, but ...

When you put them next to each other, you can see that ...For example ...


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Are these

two colors

the same?

They are different colors!

Set tolerances accordingto ...... how noticeable the part is and manufacturing conditions for the part.When a product is assembled, there are some parts which are very noticeable andother parts which are less noticeable. Because of this, although tight tolerances shouldbe set for very noticeable parts, setting looser tolerances for parts which are lessnoticeable is acceptable.

V ti bl t L ti bl t


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Very noticeable part Less noticeable part

Tolerances

L*=1.0

a*=0.3

b*=0.5

Tolerances

L*=1.4

a*=0.5

b*=0.7

Note: Tight and loose tolerances should differ up to around 0.5 in terms of E*ab.

Set tolerances accordingto ...... how noticeable the part is and manufacturing conditions for the part.

Depending on part characteristics such as shape, etc., there are cases where it isdifficult to paint a part in the same way as for other parts, making it difficult tocontrol its color in the same way as for a standard part.In such case, feasible actual control tolerances should be provided to the customer

beforehand for approval


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beforehand for approval.

Standard part Difficult-to-paint part

Tolerances L*=1.0

a*=0.3

b*=0.5

Tolerances L*=1.4

a*=0.5

b*=0.7

Example of use of color difference E*ab

Color difference E*ab

Perception by human eye

Up to 0.1 No discernable difference between colors

0.1 to 0.2 Limit of difference discernable by skilled expert


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0.2 to 0.4 Limit of difference discernable by averageperson

0.4 to 0.8 Range used where strict control of colordifference is necessary, such as where partsare touching

0.8 to 1.5 Range which is often used in color control ofproducts

1.5 to 3.0 Range in which colors will generally appear thesame if they are lined up separately (nottouching)

Greater than 3.0 Range where complaints regarding color occur.

Greater than 12 Different color name

The color difference ( E*ab) between colors in Munsell color space is around 7.

White ellipses indicatecolor discrimination

ability of human eyes

Eyes are more sensitiveto hue changes than to

chroma changes

Differences in difference discrimination between human eyesDifferences in difference discrimination between human eyes andand

E*abE*ab

Differences in difference discrimination between human eyesDifferences in difference discrimination between human eyes andand E*abE*ab


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Hue

ChromaChroma

Eyes are more sensitiveto changes at low

chroma than at highchroma

Points requiring carewhen measuring colors


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When performing color control with tradingpartners, you need to be aware that youshould be careful of some points.

When performing color control with tradingpartners, you need to be aware that youshould be careful of some points.

Points requiring care1.1. Standardization of illuminating/viewing geometryStandardization of illuminating/viewing geometry

2.2. Standardization of illuminant/observer conditionsStandardization of illuminant/observer conditions


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3.3. Standardization of measurement positionStandardization of measurement position

4.4. Standardization of ambient temperatureStandardization of ambient temperature

5.5. Maintenance of target plates (Periodic calibration)Maintenance of target plates (Periodic calibration)

6.6. Maintenance of instrument and calibration platesMaintenance of instrument and calibration plates

Standardization of

illuminating/viewing geometry

0 8 0 0

Different illumination/viewinggeometries will give different

measurement results


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Diffuseillumination/

0 or 8viewing

Single-angleillumination/

0 viewing

Multi-angleillumination/

0 viewing

For example:Both d/8, both45/0, or bothMultiangle/0

measurement results.Be sure you both use the same one!

Standardization of illuminant/observerconditions

Be sure to use the same illuminant and observer conditions.

A

Illuminant Observer


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D65

C

For example:Both D65

For example:Both 10

Variations in color appearancedue to differences in viewing

angle


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2data 10data

Measurements of curvedsurfaces

When measuring curved surfaces, it is important totake all measurements at the same point.


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First measurement

Second measurement

First measurement

Second measurement

Standardization of measurementposition

Example of poor color control.

Companies A and B

measure different points


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AA

B

B

Target plate Sample

measure different points

Standardization of measurementposition

Example of good color control.

Companies A and B

measure the same point.

The same point is

measured every time.


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p

A

A

B

B

y

Standardization of ambienttemperatureDid you know that colors change depending on temperature?

Under direct sunlightin mid-summer

Indoors withair-conditioning


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50C vs. 23C

Standardization of ambienttemperature

Effect of temperature on color (Thermochromism)

Color change for each 1C change in temperature: (Material: Ceramic tiles)

In general, if the temperature changes, the coloralso changes. This is true for any material.


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Color White Orange Red Yellow Green Cyan Black

E*ab 0.001 0.15 0.13 0.09 0.09 0.05 0.002

g g p ( )

Either take measurements in a location that is temperature-controlled, or take measurements with both the target plate

and sample at the same temperature

Standardization of ambienttemperature

Held in handPlaced on a table


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Measurement Condition InformationWhen reporting color measurement values, be sure to include the following measurement condition information:

Measurement type Spectral type; Tristimulus type

Illumination/viewing geometry

Reflectance d/8 (SCI/SCE); d/0; 45/0; multi-angle

Transmittance d/0; 0/d; 0/0


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Illuminant D65; C; A; F2; etc.

Observer 2 Standard Observer; 10 Standard Observer

Color space L*a*b*; L*C*h; Hunter Lab; etc.

This color was measured with a

spectral instrument (model name),with d/8 (SCI) geometry under D65

illuminant and 10Standard Observer.

Do you know...?1. The instrument being used?

2. The illuminating/viewing geometry of the instrument?

3. The illuminant and observer being used?4


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4. ...

Please be sure to check this information Ask your customer/supplier/partner

If you have any questions, please ask us!

Examples of use invarious industries

Examples of use invarious industries


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various industriesvarious industries

PVC profiles for windows andinterior finishing:

Deceuninck

Thyssen Polymer

PVC profiles for windows andinterior finishing:

Deceuninck

Thyssen Polymer

Household appliances(plastic, painted andmetal parts):

LG

Household appliances(plastic, painted andmetal parts):

LG

Some references from plastc applications


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Vox Industie

Wavin

VekaDecora (PL)

Salag (PL)

Aluplast (PL)

Kaczmarek (PL)

Vox Industie

Wavin

Veka

Decora (PL)

Salag (PL)

Aluplast (PL)

Kaczmarek (PL)

Samsung

Whirlpool

Electrolux

BSH (Bosh & Siemens)

Amica (PL)

Zelmer (PL)

Samsung

Whirlpool

Electrolux

BSH (Bosh & Siemens)

Amica (PL)

Zelmer (PL)

Paints, plasters,building materials

Paints, plasters,building materials

Examples of applications of Colibri CCM systemComputer Color Matching

Plastic, masterbatch

Printing/packaging

Plastic, masterbatch

Printing/packaging


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Synthetic leather (PVC)Synthetic leather (PVC)

building materialsg

Automotive exterior colorAutomotive exterior color


CompareMeasurement points

Photograph is an image only, and is not directly connected to the explanation contents


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Compare




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Checking color difference betweenfender and bumper

Photograph is an image only, and is not directly connected to the explanation co

Points for evaluating exterior colorPoints for evaluating exterior color


Metamerism

Sample Substrate Paint

Paint materials are different.


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Color sample Metal Baked paint

Body Steel Baked acrylic

Bumper Plastic AcrylicurethaneDoor mirror Plastic Acrylicurethane

Spoiler Plastic Acrylicurethane

Face/Flop characteristics

B i ht d l




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Brightness and color varyaccording to the viewing

angle.

Perform evaluation using the colordifference L*C*H* at each angleand the FF (face/flop) value.

Color difference at each angle



E*ab 2.0


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E*ab 3.3

E

*

ab

4.5

25

45

75

25

45

75

Lightsource

Sensor

Lightsource

Lightsource

Lightsource

Lightsource

Lightsource

Sensor

Index indicating the degree of brightnessdifference between highlight and shade

angles

Face/Flop characteristicsFace/Flop characteristics

Face/Flop characteristicsFace/Flop characteristics


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FF (Face/Flop) value =L* (25; Highlight)/L* (75; shade)

Orientation of lustermaterial is uniform,

causing specularreflectance to be high

Orientation of lustermaterial varies, causing

diffuse reflectance to behigh

Large FF value SmallFace/Flop


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reflectance to be high. high

Automotive interior colorsAutomotive interior colors



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CM-2500c : easy measurement of samples withcurved surfaces such as automotive parts or soft

samples.

45/0 geometry


Automotive interior colorsAutomotive interior colorsCM-700d / 600d NEWSpectrophotometer (spectral type)

Compact portable


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spectrophotometer with wirelesscommunication and color LCD

screen


Automotive interior colorsAutomotive interior colorsCompare


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Compare

Compareograph is an image only, and is not directly connected to the explanation contents.

Instrument panel top vs. Door tr

Glove compartment vs. Lever


Automotive interior colorsAutomotive interior colorsPhotograph is an image only, and is not directly connected to the explanation


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Steering wheelvs. Horn pad

Horn pad vs.Steering wheelswitches

Seat trim vs. Scuff plate

Comparing materials with diverse surface conditions




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Leather texture(Synthetic leather)

Leather texture(Plastic)

Geometric texture(Plastic)

Matte finish(Paint)

When surface conditions are greatly different, view the samplesfrom an angle so that the reflected image of the light source does

not reach your eyes.

Optimum color-measuring instrument: 45 illumination/0 viewinggeometry

Glass colorsGlass colors

Glass colorsGlass colors


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Ideal for Long Glass oracrylic which neednot

be cut formeasurements

CM 5

Toploading Reflectance &Transmittance

Spectrophotometer

ConclusionConclusion

ConclusionConclusion

Color-measuring instruments are used formeasuring the color of an amazing range ofobjects, from cars to foods, paints, plastics,textiles, appliances, building materials,

cosmetics, paper, etc., even people's skin!

Let us help you with the latest in color


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Let us help you with the latest in colorknowledge including color-measuringinstruments, color-difference control, etc., so

that you can make full use of color-measuringinstruments in your day-to-day work.

Konica Minolta Sensing

Manish KapadiaJay Instruments & Systems Pvt. Ltd.

India

Auto Color Seminar JISL MK

Documents

Transcript of Auto Color Seminar JISL MK