Automotive Interior and Exterior Weathering Testing 1
Automotive Interior and Exterior
Weathering Testing
Q-Lab Corporation
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Automotive Interior and Exterior Weathering Testing 2
Today‘s Agenda
• Weathering of automotive components
• Weathering science basics
• Natural outdoor testing
• Accelerated Laboratory testing
• Automotive test methods and correlation to observed failure
Automotive Interior and Exterior Weathering Testing 3
Weathering of Automotive Components
Why is it worthwhile to conduct weathering testing?
Automotive Interior and Exterior Weathering Testing 4
Weathering of Auto ExteriorsColor change and gloss loss
Automotive Interior and Exterior Weathering Testing 5
Weathering of Auto ExteriorsPhysical and Chemical failures
Cracking
Blistering
Automotive Interior and Exterior Weathering Testing 6
Weathering of Auto ExteriorsPhysical and Chemical failures
Delamination
Adhesion,Chipping
Automotive Interior and Exterior Weathering Testing 7
Weathering of Auto InteriorsPhysical and Appearance failures
CrackingColor fade
Automotive Interior and Exterior Weathering Testing 8
Why Do Weathering Testing?
Weathering testing can mean the difference between happy customers and … the customer on the right
High gloss and color integrity
Fading, cracking, peeling
OR
Automotive Interior and Exterior Weathering Testing 9
Why Do Weathering Testing?
Weathering testing can mean the difference between happy customers and … the customer on the right
High gloss and color integrity
Corrosion resulting from failed coatings
OR
Automotive Interior and Exterior Weathering Testing 10
Weathering Science Basics
Why do interior and exterior automotive components fail in service?
Automotive Interior and Exterior Weathering Testing 11
What is Weathering?
Changes in material properties resulting from exposure to the radiant energy present in sunlight in combination with heat(including temperature cycling) and water in its various states, predominately as humidity, dew, and rain.
Automotive Interior and Exterior Weathering Testing 12
Forces of WeatheringKnow Your Enemy!
• Sunlight
• Heat
• Water
*Other factors can impact weathering as well but we will not focus on those today
Automotive Interior and Exterior Weathering Testing 13
Ultraviolet (UV) light is responsible for most weathering degradation
UV is only 7% of the sunlight spectrum but it causes virtually all polymer degradation!
Automotive Interior and Exterior Weathering Testing 14
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
250 300 350 400 450 500 550 600 650 700 750 800
Wavelength (nm)
Outdoor sunlight
Sunlight behind window glass
Sunlight Outdoors vsSunlight Behind Window Glass
Spectral Irradiance
(W/m2/nm)
This difference between UV light in outdoor-and behind-glass service environment is a major factor in weathering behavior
Automotive Interior and Exterior Weathering Testing 15
Factors Affecting Automobile Glass UV Light Filtering
• Tint
• Thickness
• Lamination
Automotive Interior and Exterior Weathering Testing 16
Heat Effects
• Dimensional change
• Evaporation
• Thermal aging
• Thermal cycling
Automotive Interior and Exterior Weathering Testing 17
Temperature and ColorDarker Colors Have Higher Temperatures!
Temperature Δ (°C)
0
-5
-10
-15
-20
-25
Automotive Interior and Exterior Weathering Testing 18
Heat behind Window Glass
Temperature of automobile interior components behind window glass
can exceed 100 °C
Automotive Interior and Exterior Weathering Testing 19
Major Effects of Water
Chemical Reactions
– Reactions in solution
– Facilitates reaction via increase in oxygen transport
Physical Effects
– Erosion
– Absorption/freeze-thaw
– Thermal shock
– Impact (material loss)
Automotive Interior and Exterior Weathering Testing 20
Water in Service Environments
Humidity Rainfall Dew
• Affects time of wetness• Exterior and interior
• Washing of surfaces• Chalking• Thermal shock
• High O2 content• Long dwell time
PRIMARY SOURCE OF OUTDOOR WETNESS
Automotive Interior and Exterior Weathering Testing 21
Natural Outdoor Weathering Testing
Benchmark test data from realistic exposures
Automotive Interior and Exterior Weathering Testing 22
45° south-facing panel exposure
Automotive Interior and Exterior Weathering Testing 23
0° Exposure Angle, mesh backing forthree-dimensional components
Automotive Interior and Exterior Weathering Testing 24
Black Box Testing
• Imitates auto trunk
and hood conditions
• Developed by GM in
1950’s
• High temperature
• SAE J1976
Automotive Interior and Exterior Weathering Testing 25
Under-Glass Exposures for Interior Components
Automotive Interior and Exterior Weathering Testing 26
Whole Car Testing
• Testing of entire vehicle
• Best simulation of the end use –includes exterior and interior weathering
• All parts, materials and components interact during the weathering process
• Thermal radiation studies commonly performed
Automotive Interior and Exterior Weathering Testing 27
Accelerated Outdoor Weathering Testing
Realistic exposures done faster
Automotive Interior and Exterior Weathering Testing 28
AIM Box“Automotive Interior Materials” Box
• Reproduces extreme heat from
automotive interior
• Can test entire instrument panel
• Different plastics experience
different thermal expansion
• Generates differential stresses
between different interior plastics
Automotive Interior and Exterior Weathering Testing 29
Natural Sunlight ConcentratorQ-TRAC
Automotive Interior and Exterior Weathering Testing 30
Natural Sunlight ConcentratorQ-TRAC
• Tracks the sun during the day• Delivers 5× as much UV as a natural exposure• Fast results with natural solar spectrum
Automotive Interior and Exterior Weathering Testing 31
Laboratory Weathering Testing
Accelerating testing for faster results than outdoor
Automotive Interior and Exterior Weathering Testing 32
Xenon Arc Test Apparatus
Rotating rackFlat array
Automotive Interior and Exterior Weathering Testing 33
Optical Filters
• Daylight (for exterior components)
• Window (for behind-glass interior components)
• Extended UV (for harsh testing, quality control)
Rotating drum “lantern” filter
Flat array filter
Automotive Interior and Exterior Weathering Testing 34
0.0
0.5
1.0
1.5
260 280 300 320 340 360 380 400
Spectral Irradiance
(W/m2/nm)
Wavelength (nm)
Daylight
Daylight Filter
Window Filter
Extended UV filter
Xenon and Sunlight Spectra
Extended-UV Filter
Window Filter
Daylight
Daylight Filter
Automotive Interior and Exterior Weathering Testing 35
Black Panel Temperature Control
• Most common in test standards
• Approximates maximum specimen surface temperature
• Can be used in combination with chamber air temp sensor and control
Automotive Interior and Exterior Weathering Testing 36
Black PanelTemperature Sensors
PanelASTM (ISO)Designation
Typical use
Uninsulated Black Panel (Black Panel)
Metallic substrates (painted metal)
Insulated Black Panel (Black Standard)
Insulating substrates (polymers)
Automotive Interior and Exterior Weathering Testing 37
Chamber Air Temperature Control
• Required by certain test methods
• Necessary for control of RH
• BP temp always hotter than chamber air temp from absorbing radiant heat
Automotive Interior and Exterior Weathering Testing 38
Relative Humidity Control • Required by many test methods
– Textiles
– Automotive (SAE)
• Many xenon testers can generate and control
relative humidity
– Boiler-type system
– Nebulizer system
• For many durable materials, RH makes very
little difference compared to spray and
condensation
Automotive Interior and Exterior Weathering Testing 39
Xenon ArcWater Spray
Front spray
– Primary method of water delivery
– Calibration technique for front spray recently developed (ASTM D7869)
Back spray
– Result of a failed experiment intended to generate condensation; persists in some standards
Dual spray
– For delivering a 2nd solution, e.g. acid rain, soap
Immersion (Ponding)
– Alternative to front spray called out in some standards
Automotive Interior and Exterior Weathering Testing 40
Fluorescent UV Test Apparatus
Automotive Interior and Exterior Weathering Testing 41
QUV Lamps
• UVA-340 (for exterior components)
• UVA-351 (for behind-glass components)
• UVB-313EL (for harsh testing, quality control)
Automotive Interior and Exterior Weathering Testing 42
QUV Lamp and Sunlight Spectra
0.0
0.5
1.0
1.5
260 280 300 320 340 360 380 400
Spectral Irradiance
(W/m2/nm)
Wavelength (nm)
Daylight
UVB-313
UVA-340
UVA-351
UVB-313
UVA-351
Daytime sunlight
UVA-340
Automotive Interior and Exterior Weathering Testing 43
QUV Color Temperature
• Xenon testers generate IR heat and reproduce outdoor color temp. differences
• UV fluorescent testers do not
Fischer and Ketola, 1993
Temperature Δ (°C)
0
-5
-10
-15
-20
-25
Automotive Interior and Exterior Weathering Testing 44
QUV Condensation• Closest match to natural
wetness
• Best way to accelerate water in an laboratory tester
• Elevated temperature
• High O2 content
• Tester performs distilling – you cannot deposit debris on specimens! Water is guaranteed to be clean.
Creating condensation in the QUV is easy and does not require expensive, pure
water
Automotive Interior and Exterior Weathering Testing 45
QUV Water Spray
• Ensures that parts get fully saturated
• Creates erosion & thermal shock
Automotive Interior and Exterior Weathering Testing 46
Fluorescent UV & Xenon Comparison
Xenon
Fluorescent UV
Costeffectiveness
Reproducibility
UV lightspectrum
Full sunlightspectrum
Realisticmoisture
Automotive Interior and Exterior Weathering Testing 47
Automotive Accelerated Laboratory Testing
Driving towards better correlation with outdoor weathering
Automotive Interior and Exterior Weathering Testing 48
Historical Test Standards
• Xenon arc’s light sources have been used for many years -accurate reproduction of full-spectrum sunlight
• Hardware-based “102/18” light/light+spray standards were the first widely-used weathering standard tests– Almost 100 years old but still in use
– Most common example is ISO 4892-2
– Not realistic!
• SAE J2527 became the “state of the art” in 1980’s– Research into primary stressors (light, water, heat)
– Replicated gloss loss seen in Florida exposures
– Does not match all real-world failure modes
Automotive Interior and Exterior Weathering Testing 49
Taking the Next Step:ASTM D7869
• Outdoor weather data collected to understand real-world weather conditions: light, heat, and water
• Outdoor weathering test dataset collected to provide basis for correlation
• Accelerated test cycle developed to match those real-worldconditions and degradation mechanisms
• Variety of materials and failure modes evaluated with accelerated testing to verify validity of test
Automotive Interior and Exterior Weathering Testing 50
Weathering Standard DevelopmentFeatures of ASTM D7869 Test Protocol
• Better match with sunlight spectrum– New optical filter, increased intensity
• Better match to outdoor temperature profile– Realistic temperatures chosen
– At or below maximum experienced outdoors
• Better match to outdoor wetness conditions– Significantly longer time of wetness
– Water delivery calibration system devised
Automotive Interior and Exterior Weathering Testing 51
ASTM D7869Reproduces Natural Weather Cycles
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 2 4 6 8 10 12 14 16 18 20 22 24
Time (hours)
Irra
dia
nce
(W
/m2/n
m@
34
0n
m) Deep Water
Penetration
Adhesion, Blistering, Diffusion
No spray during light steps
Avoids unrealistic
failures
Cyclic Stresses (cracking)
Surface Erosion (gloss)
Irradiance
Water Spray
Automotive Interior and Exterior Weathering Testing 52
Florida Exposure SAE J2527 ASTM D7869
ASTM D7869 ValidationCoating Pick-Off
Expected Failure Mode: Slight BC/E-coat pick off
Observed: Slight BC/E-coat pick-off ASTM D7869, not SAE J2527
Automotive Interior and Exterior Weathering Testing 53
ASTM D7869 ValidationGloss and Adhesion Loss
Expected Failure Mode: Blistering, gloss loss, adhesion loss
Observed: Gloss and adhesion loss on both. Blistering ASTM D7869
×
Florida Exposure SAE J2527 ASTM D7869
Automotive Interior and Exterior Weathering Testing 54
ASTM D7869 ValidationBlistering
Expected Failure Mode: Blistering, gloss loss, adhesion loss
Observed: Gloss loss and adhesion loss seen on all panels. Blistering on ASTM D7869 mimics that seen on Florida
Florida Exposure SAE J2527 ASTM D7869
Automotive Interior and Exterior Weathering Testing 55
Validation Testing of ASTM D7869
• Chemical change correctly reproduced
• Cracking correctly reproduced
• Blistering correctly reproduced
• Adhesion loss correctly reproduced
• Color correctly reproduced
• Gloss loss correctly reproduced
Automotive Interior and Exterior Weathering Testing 56
Summary – Automotive Weathering Testing
• Automotive exterior and interior materials experience a wide range of physical and chemical degradation from sunlight, heat, and water in service environments
• Natural outdoor test methods like Black Box, Under-glass, and whole carcan simulate automotive conditions
• Accelerated outdoor tests like AIM Box and natural solar concentratorprovide enhanced testing outdoors
• Xenon arc and fluorescent UV accelerated test chambers can provide results in a shorter timeframe
• New test protocols like ASTM D7869 offer better correlation to outdoor environments than historical test standards
Automotive Interior and Exterior Weathering Testing 57
Thank you for your attention!
Questions?
Color & Appearance of Automotive Interior & Exterior
• The interior is getting more and more important
influences purchasing decisions
quality requirements are increasing
• New materials to save cost: molded in color
• New looks:
- Natural leather look
- Synthetic Hi-tech look
- Everything has to be very low gloss - mat
- Customer should perceive a higher value
Automotive Interior
• Textile: body cloth, headliner, carpet, webbing, seat belts
• Plastic Parts:
- Hard tooled, uncoated, structured surfaces
- Hard tooled, coated, structured surfaces (soft touch)
- Soft tooled: Slush or film (instrument panel, visor)
• Coated metal parts
• Leather (real and artificial leather)
Automotive Interior: Variety of Materials
• Color and Appearance need to be harmonized
• Very tight tolerances are requested:
Objective and reliable testing instruments are needed
Automotive Interior Specifications
Typical Tolerances:
Color: L*, a*, b* ± 0.5
Gloss 60° : < 5 GU ± 0.3 … 0.5
Automotive Interior Gloss
Specular Reflection
(= Gloss)
Diffuse Reflection
Specular Gloss Reflection
Incident light
ObserverIllumination
Surface
How is Gloss Perceived?
polished
Glossy Surface
rough
Medium to Mat Surface
Glossmeter Design
α1 ± 0.1° α2 ± 0.1°
e.g. Receptor aperture
20°: 1.8° ± 0.05°
20°
85°
60°
Defined Angles of Illumination
Semi 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
Angles of Illumination
60°
85°
20°
Visual Gloss
Measured
Gloss
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
Recommended Geometries
Page 14, BYK-Gardner GmbH, Automotive Interior
• Color and Appearance need to be harmonized
• Very tight tolerances are requested:
Objective and reliable testing instruments are needed with
superior technical performance
Automotive Interior Specifications
Typical Tolerances:
Color: L*, a*, b* ± 0.5
Gloss 60° : < 5 GU ± 0.3 … 0.5
0-10 GU>10 GUGloss range:
± 0.1± 0.2Repeatability:
± 0.2± 0.5Reproducibility:
Increased Accuracy for 60° gloss in the mat range
micro-gloss S spectro-guide S
0-10 GU>10 GU
± 0.1± 0.2
± 0.5± 1.0
Color E*
0.01 1
0.2 1
The Right Tools for Toughest QC Requirements
Detector
Gloss value dependent on refractive index of material - ASTM D523 – ISO 2813
GU
100
0
black glass standard - refractive index 1,567
Gloss value dependent on refractive index of material - ISO 2813: Polished black glass
Gloss value dependent on refractive index of material: e.g. High-gloss clear coat
20° GU
Visual:
Same brilliance
No correlation
Refractive index
1.541.521.51 1.531.50
80
85
90
95
1 K
2 K
91 82
Non-metal e.g. paint, plastic
Reflectance Gloss Units
20° 0 ... 5 % 0 ...100
60° 0 ... 10 % 0 ...100
85° 0 ... 65 % 0 ...100
Metal e.g. aluminum
Reflectance Gloss Units
20° 0 ...100 % 0 ...2000
60° 0 ...100 % 0 ...1000
85° 0 ...100 % 0 ... 160
100 %Polished black glass:
~10 % at 60°
Auto range: highly reflective metals
100 %Reflectance
...100 %
n=1,567
Automotive Interior Color
Color Perception
Light Source
Object
Observer
Standard illuminants
Eye Detectors
Cone cells
Color detectors
Rod cells
Lightness detectors at night
Cones
Retina
Rods
Cones
Cones
ObserverLight source
Masking Screen
Black Partition
Wright / Guild Experiment
Standard Observer
400 500 600 700
Wavelength (nm)
10° Observer (1964)
2° Observer (1931)
z y x
Re
lati
ve
En
erg
y
observer
object
Gloss Absorption Diffusion
Interaction between Light and ObjectGloss, Absorption and Diffusion
• Direct Reflection on surface – Gloss
• Light is absorbed by Pigments and dyes – Absorption
• Light is scattered by Pigments – Diffusion
yellow
red
green
blue
Object Color Spectral Reflectance Curves
Measurement Principle: Spectrophotometer
Sample
Light source
Monochromator
% R
efle
ctio
n
Wavelength
Red
Spectral data
L* Lightness
a* green / red
b* blue/yellow
L* Lightness
C* Chroma(saturation)
h° hue angle
CIE L*a*b*-System – Opponent Color Space
E* = √ (L*)2 + (a*)2 + (b*)2
= Sample - Standard
- +
- +
- +
L*
a*
b*Sample
E*
L*
b*
a*
Standard
CIELab - System: Color Difference L*, a*, b*
Color and gloss influence the
visual impression
The structured part looks lighter,
despite being made of the same
colored material!
Does the color match?Do the two sides look different?
Typical Applications:
• Comparison to defined standard
• Batch-to-batch control
• Harmonization of various
materials/structures
Differences in gloss/ structure Color Differences
Circumferential illumination reduces directionality influence
Visual Perception: 45/0 Geometry
45/0 Geometry
0123456789
10
Refl
ec
tio
n
Glossy
Matt
dL* = 4,79
da* = 0,26
db* = -0,04
dE* = 4,79
nM
45/0 Geometry evaluates Color “as we see it”
Typical Applications:
• Color matching
• Color strength development
• Weathering studies
Differences in gloss/structure Color DifferencesX
Color Hue Control: Sphere Spin
Sphere spin Geometry
0123456789
10
Re
fle
cti
on
Glossy
Matt
dL* = 0,06
da* = 0,09
db* = -0,01
dE* = 0,10
nM
Spin Geometry evaluates Color Hue
* Specular Included
color
pigmentation
delta E* = 0
sphere SPIN *
color as we see it
delta E* = 3
45°
0°
45/0
Comparison: 45/0 - sphere spin
Color Differences
Check the
color hue
sphere spin sphere spex
Check visual
agreement
Gloss Differences
Shortcut with limitations
How to measure the visual difference?Compare spin and spex color values
Differences in gloss/structure Color Differences
Good correlation to 45/0 on high gloss surfaces!
Advantage:
• Diffused illumination ---> influence of
directionality reduced
• Disadvantage:
Correlation to 45/0 diminishes with
lower gloss levels --> gloss trap does
not capture all the diffused light from
the specular reflection
DetektorDetector
8° observer
Buffer
Buffer
Diffuse illumination
Sample
Gloss trap
Visual Perception: Sphere Spex
Managing Automotive Standards
Color Harmony Controlwithout Digital Standard
Master Standard
-1.5
-1
-0.5
0
0.5
1
1.5
-1 -0.5 0 0.5 1
Certified working standards
Every plant uses
their Certified
Working
Standards for
instrumental
control
Sources of error:
• Working standards differ from each other
• Operator influence
• Inter-instrument variation
Practical Consequences:
Lot’s of room for discussion: Is measured color difference a “real difference”?
Visual color approval becomes more significant
Subjective color approval!
Color Harmony Controlwithout Digital Standard
Digital Standards
Digital Standards bring the complete supply chain on target!
• One binding reference
• Minimize error sources: Electronic instrument standards take place of certified master standards
• Only instruments with excellent accuracy between instrumentsallow usage of Digital Standards
Benefit of Digital StandardOne binding reference
+ b*
- b*
+ a*- a*
Plants & suppliers use the
same „master-master“ panel
Digital Master Standard for
instrumental controlExcellent inter-instrument
agreement
Automotive Exterior Color & Appearance
Effect Coatings80% of automotive finishes are effect coatings
• Pearlescent coatings result in a more spectacular color effect: Color Flop
• Metallic coatings accentuate the curved profile: Light – Dark Flop
• Effect finishes with special glitter effect (XirallicsTM)
Pigment Types and Interaction with Light
Pearl Luster
Pigments
specific color, luster
and color flop
due to interference of light
Metallic
Pigments
metallic gloss
due to mirror-like reflection of light
Absorption
Pigments
specific color
due to selective absorption and
scattering of light
Multi-angle Measurement GeometriesAspecular viewing angles
Multi-angle Measurement GeometriesSpectral reflectance – Solid Green
0
5
10
15
20
25
30
35
nm
R%-15°
15°
25°
45°
75°
110°
Multi-angle Measurement GeometriesSpectral reflectance – Metallic Green
0
5
10
15
20
25
30
35
nm
R%- 15 °
15 °
25 °
45 °
75 °
110 °
Multi-angle Measurement GeometriesSpectral reflectance – Metallic Silver
0
50
100
150
200
250
300
350
nm
R
%
- 15 °
15 °
25 °
45 °
75 °
110 °
Traditional 5-angle
-120
-80
-40
40
80
120
-120 -80 -40 40 80 120-a*
-b*
+b*
+a*New: -15° angle
Color changes with Viewing Angles
Visual Effect Judgment
Appearance of effect finishes depends
on illumination conditions:
Sunny sky: Direct illumination
• Color starts to sparkle
Cloudy sky: Diffused illumination
• Fine versus grainy pattern
Color Measurement of Effect Finishes
• Color is the integral of the spectral
reflection over the measured area
Often visual disagreements
• No differentiation between basecoat
color and reflection of effect flakes
• Special effect pigments
cannot sufficiently be
characterized (Xirallics,
Interference pigments)
Total Color Measurement of Effect Finishes
Goal:
Develop a solution to characterize the total color
impression
• Color perception changes with viewing angles:
Multi-angle color measurement
• Color perception changes with viewing conditions:
Flake characterization
Visual Appearance of Effect Finishesunder direct illumination
Sparkle: Micro brightness – Glints – Diamonds
Viewing conditions:
• Spotlight ~ direct sun light conditions
• Observation angle critical:Sparkle impression changes
with illumination angle
Sparkle is generated by e.g.:
• Reflectivity of the individual effect
pigment (alu flakes, mica, Xirallics)
• Amount of effect pigments
• Size of the aluminum flakes
High
Sparkle
Low
Sparkle
Visual Appearance of Effect Finishesunder diffused lighting
Graininess:
Texture – Structure – Coarseness – Salt & Pepper
Viewing conditions:
• Diffused light
• Close observation distance
• Observation angle not important
Potential causes of graininess:
• Flake type – flake size
• Disorientation of flakes
• Agglomeration of particles
High
Graininess
Low
Graininess
Flake CharacterizationEvaluation of the optical properties of effect particles
• Camera Analysis: The spatial resolution of the CCD chip correlates to the spatial resolution of the human eye.
• Camera pictures are taken
under different light conditions
to simulate sunny sky and
cloudy sky.
• The sparkling impression is
evaluated under 3-illumination
angles: 15°- 45°-75°
Camera pictures characterize Sparkle and Graininess
Flake Characterization – Sparkle Effect
Analysis of Sparkle Images:
• Sparkle area is detected:
The higher the number – the more flashes
that have occured
• Sparkle intensity is measured:
The more intense the flash, the higher the number
• Sparkle area and intensity are combined
to determine total Sparkle Grade
Improved Color Difference Equations
Standard
Sample 1
Sample 2
1
2
E* = √(L*)2 + (a*)2 + (b*)2
Component DifferencesDetermine the cause of a mismatch
E* = √(0.0)2 + (1.0)2 + (0.0)2 = 1
E* = √(0.57)2 + (0.57)2 + (0.57)2 = 1
Limitations of CIELAB System:Measured deltas 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 changes 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.
± a*
Product Standard
Acceptable Match
L*a*b* Tolerances for achromatic colors
± b*
Visually Rejected Match
• Circle tolerance agrees
well with visual perception
• Rectangular tolerances
approximate a circle
± a*
Product Standard
Acceptable Match
L*a*b* Tolerances for chromatic colors
± b*
Visually Rejected Match
• Elliptical tolerance agrees
well with visual perception
• Rectangular tolerances
doesn‘t agree well with
visual perception
+ a*
Product Standard
Acceptable Match
L*C* h Tolerances for chromatic colors
+ b*
Visually Rejected Match
h°
C*
• Elliptical tolerance agrees
well with visual perception
• Pie LCH tolerances
approximate an ellipse
CIELAB - System: Chromatic – Non Chromatic
+ b*
- b*
+ a*- a* B
P
C*
H*
Non-chromatic colors: C* < 10
Use ∆ L*a*b*
Chromatic colors: C* > 10
Use ∆ L*C*h°
Color SystemsImproved visual agreement on solids
ECMC E94 E00
CIE-L*a*b*
Goal:
• Better agreement with visual color perception
• One tolerance for all colors = uniform color space
ECMC – Color Measurement Committee of The Society of Dyers and Colorists (UK): 1984
• 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 on perception
E94 - Color Difference Formula: 1995
• Based on visual evaluation of new sample sets – solid colors only
• Currently published in the following CIE recommendation:
- CIE Technical Report 116: Industrial Colour Difference Evaluation
• Based on elliptical spacing and Delta L*C*H*
• Corrects only for chroma dependent perception of chroma and hue
• No lightness correction
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*
• Five corrections to CIELab:
• Corrects for lightness, chroma and hue dependent perception
• Rotation function improving the performance for blue colors
• Factor for rescaling the a*-axis: improved performance for grey colors
DIN 6175- Part 2: Tolerances for Automotive Paints
• Based on visual evaluation of metallic samples
• Uses weighting functions dependent on color of standard
• Uses additional factors to differentiate between application requirements (=G-factors):
- Delivery of paint batch
- Paint line, add-on parts, repair line
Color Systems for Automotive Exterior Applications
E*
E‘DIN
Optimized for
metallic finishes
Optimized for solid,
high chroma colors
ECMC E94
E00
Thank you for your attention.