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Exploring the Concepts of Color and Gloss
Jeralyn CampBYK Gardner
May 2-3, 2016
Color stimulates certain Feelings!
Color stands for Identification!
Color stands for Regulation and Authority!
Color influences our Purchasing Decisions!
Uniform Color : Multi-component Products
Visual Assessment
• Color perception is subjective- Age, gender, mood
• We cannot communicate nor remember colors- Only names or numbers
• Color is dependent on surrounding light
• Color is dependent on background
Page 8, BYK-Gardner USA, Color Measurement
Page 9, BYK-Gardner USA, Color Measurement
Colors seem more dramatic against black
Colors seem more subdued against white
Color Perception Light Source
Object
Observer
D65 / 10°spectro-guide 45/0
Color Scale Standard Sample Differences
L* 36.84 37.77 0.93a* -24.10 -24.59 -0.49b* 12.00 11.88 -0.12
dE* = 1.05
Measurement Report illuminant
Spectrum of Visible Light object
Wavelength l (nm)
1 nm = 10-9 m
UV IR
White light is a mixture
of many colors
Standard illuminants
400 500 600 700
Wavelength [nm]
F2E l
400 500 600 700
Wavelength [nm]
E l
A
400 500 600 700
Wavelength [nm]
E l
D65
North Sky Daylight Tungsten Fluorescent
Ojects look different under different illuminants
D65 / 10°spectro-guide 45/0
Color Scale Standard Sample Differences
L* 36.84 37.77 0.93a* -24.10 -24.59 -0.49b* 12.00 11.88 -0.12
dE* = 1.05
Measurement Report observer
Eye Detectors
Cone cells
Color detectors
Rod cells
Lightness detectors at night
Cones
Retina
Rods
Cones
Cones
Young/Helmholtz Color Theory
Primary wavelengths:700 nm (red)546 nm (green) 435 nm (blue)
Wright / Guild Experiment
Observer
Masking Screen
Black Partition
The Eye and Fields of View
2° observer (1931)
• Small area of the retina
• Does not agree with color viewing
10°
10° observer (1964)
• Large area of the retina
• Corresponds with color viewing
Standard Observer
10° Observer (1964)
2° Observer (1931)
400 500 600 700
Wavelength (nm)
Rela
tive
En
erg
y
•Dichromacy: only 2 cones are functioning• Red blindness (approx. 1% of male)
• Green blindness (approx. 1% of male)
• Blue blindness (very seldom: 1-2 in 100,000)
•Anomalous Trichromacy: 3 cones – 1 cone is altered• Most popular case (approx. 5.9 % male) e.g. red-green deficiency
Ishihara`s Test for color deficiency
Color Perception Light Source
Object
Observer
Opaque Samples
Incident Light
Specular Reflection
(= Gloss)Diffused Reflection
Opaque Samples: Absorption and Diffusion of Light
Incident light
Specular Reflection
(= Gloss)Diffused Reflection
Object Color Spectral Reflectance Curves
yellow
red
green
blue
The Building Blocks of Color
× ×
Illuminant
400 500 600 700
Wavelength [nm]
E l
AA
Observer
2°
Object
Color Scales: X Y Z L*a*b*, ....
Opponent Color Theory
B
R
A
I
N
Blue detectors
Blue - Yellow Signal
Black - White
Signal
Red - Green Signal
Green detectors
Red detectors
Page 29, BYK-Gardner GmbH, Color Measurement
Page 30, BYK-Gardner GmbH, Color Measurement
CIE L*a*b*-SystemL* Lightness
a* green / red
b* blue/yellow
L* Lightness
C* Chroma(saturation)
h° hue angle
CIELab - System
L* = + 58,12
C* = + 47,32
h° = 50°
L* = 0
L* = + 58,12
a* = + 36,26
b* = + 30,41
L* = 100
+a*
-a*
+b*
-b* Blue
Red
Green
Yellow
D65 / 10°spectro-guide 45/0
Color Scale Standard Sample Differences
L* 36.84 37.77 0.93a* -24.10 -24.59 -0.49b* 12.00 11.88 -0.12
dE* = 1.05
Measurement Report scales
Metamerism – 2 samples: pigments with different reflectance
D65 Daylight
match
A Tungsten
mismatch
% Reflectance
Metamerism Index MI
< 1 (spectrum needed)
Instrument´s Display of MetamerismD65/10°
dL* = 0,10
da* = 0,05
db* = 0,05
dE* = 0,12
A/10°
dL* = 0,08
da* = -1,04
db* = 0,10
dE* = 1,04
F11/10°
dL* = 0,06
da* = -1,62
db* = 0,06
dE* = 1,62
Metamerism Index
D65/10° - F11/10° 1,64
D65/10° - A/10° 1,06
F11/10° - A/10° 0,57
Limitations of CIELab System
Standard
Sample 1
E * = 0.57 0.57 0.57 = 12 2 2
Sample 2
E * = 0.0 1.0 0.0 = 12 2 2
E* = (L*)2 + (a*)2 + (b*)2
Limitations of CIELab SystemMeasured values do not correlate with visual impression
• Visual acceptability is based on ellipses not circles: Tolerances for hue are tighter than for chroma
• Chromatic colors have larger tolerances than pastels or near neutrals
• Size and shape of ellipse change dependent on the hue: Acceptable color differences vary from color to color Green has larger tolerances than dark blue
All colors within one ellipse are perceived as the same color.
Rectangular versus Elliptical Tolerances
± a*
Product Standard
Acceptable Match
± b*
Visually Rejected Match
Improvements of CIELab System
•Goal:• Better agreement with visual color perception
• One tolerance for all colors = uniform color space
dE*CMC
DIN99dE00
dE*94
ECMC – Color Measurement Committee of The Society of Dyers and Colorists (UK): 1988
• Based on visual evaluation of textile samples
• Currently specified in the following standards:- British Standard BS6923- American AATCC Test Method 173- ISO International Standard 105-J03
• Based on elliptical (not rectangular) spacing and L*C*H*
• Corrects for chroma, hue and lightness dependent perception
ECMC – Color Difference Formula
• 3-dimensional ellipsoid with axes corresponding to
hue, chroma and lightness
• Weighting factors (= semi-axis) SL, SC and SH
are dependent on color of standard
• Application factors l and c to modify the lengths of
semi-axes
212
ab
2
ab
2
:CMC
*H*C*LE
=
HCL
clScSlS
÷ ÷÷
lSL
HS
ccS
ECMC – Color Difference Formula
dECMC (l:c) = dL*
lSL( )2
+(dC*ab
cSC )2
+ )dH*ab
SH
2
(Where SL = 0.040975 L1 Sc = 0.0638 C1 + 0.638
1 + 0.01765 L1 1 + 0.0121 C1
Unless L1 < 16 when SL = 0.511
And SH = SC (Tf + 1- f) where f = (C1)4 1/2
(C1)4 + 1900( )
T = 0.36 + 0.4*cos( h1 + 35) unless h1 is between 164 and 345 when:
T = 0.56 + 0.2*cos( h1 + 168) where L1, C1 and h1 relate to the standard
ECMC – Color Difference Formula Better correlation to visual perception: Brilliant Yellow with Chroma / ΔHue
Chromatic colors have larger visual
tolerances in chroma than in hue
Color Difference: dE*dL*=1, dC*=1.3, dH*=0.65
Color Difference: dECMC
-4
-3
-2
-1
0
1
2
3
4
-4 -3 -2 -1 0 1 2 3 4
-4
-3
-2
-1
0
1
2
3
41
Standard; STANDARD 07
L*=84.25; a*=5.74; b*=96
45°
-dL*
+dL*+db*
-db*
+da*-da*
L* a* b* dL* da* db* dC* dH*
Standard YellowYellow -HYellow -CYellow +C
dE*
3.18 2.92 3.43
dECMC
1.64 0.88 1.02
84.25 5.74 96.0084.46 8.88 96.49 0.22 3.14 0.49 0.7384.52 5.75 93.09 0.27 0.01 -2.91 -0.1984.37 5.86 99.42 0.12 0.12 3.43 0.08
-4
-3
-2
-1
0
1
2
3
4
-4 -3 -2 -1 0 1 2 3 4
-4
-3
-2
-1
0
1
2
3
42
45°
-dL*
+dL*+db*
-db*
+da*-da*
ECMC – Color Difference Formula Better correlation to visual perception: Brilliant Red with C* vs. Brown (Less chromatic Red) with C*
Color Difference: dECMC
-4
-3
-2
-1
0
1
2
3
4
-4 -3 -2 -1 0 1 2 3 4
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1
Standard; STANDARD 09
L*=38.83; a*=33.35; b*=26.67
45°
-dL*
+dL*+db*
-db*
+da*-da*
dECMC
1.13
38.83 33.35 26.67
L* a* b* dL* da* db* dC* dH* dE*
Std Brown
Brown -C 38.69 31.14 25.21 -0.14 -2.21 -1.46 0.24 2.65
-4
-3
-2
-1
0
1
2
3
4
-4 -3 -2 -1 0 1 2 3 4
-4
-3
-2
-1
0
1
2
3
41
Standard; STANDARD 08
L*=38.64; a*=64.26; b*=52.16
45°
-dL*
+dL*+db*
-db*
+da*-da*
Color Difference: dECMC
dECMC
0.84
38.64 64.26 52.16
L* a* b* dL* da* db* dC* dH* dE*
Std Brilliant Red
Brilliant Red -C 38.59 62.06 51.11 -0.05 -2.20 -1.05 0.58 2.44
Chromatic colors have larger visual tolerance than achromatic colors.
ECMC – Color Difference Formula; Influence of ratio l : c• Ratio l:c allows for a weighting of lightness to chroma
• Most common ratio: 2:1Variation in lightness can be double
compared to chroma variations
C*H*
ratio 1:1
C*
H*
ratio 2:1
L*
L*
ECMC – Color Difference FormulaInfluence of Commercial Factor: cf
• Commercial Factor (cf) determines the overall size of the ellipse
• cf sets the color tolerance: ECMC < cf PASS
ECMC > cf FAIL L*
C*
H*
cf=1.0
L*
C*
H*
cf=0.5
ECMC – Color Difference FormulaInfluence of Commercial Factor: cf
cf = 0.5
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
-2 -1,5 -1 -0,5 0 0,5 1 1,5 2
-2
-1,5
-1
-0,5
0
0,5
1
1,5
22
Standard; STANDARD 01
L*=61,62; C*=3,47; h°=263,97
45°
-dL*
+dL*+db*
-db*
+da*-da*
cf = 1.0
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
-2 -1,5 -1 -0,5 0 0,5 1 1,5 2
-4
-3
-2
-1
0
1
2
3
42
Standard; STANDARD 01
L*=61,62; C*=3,47; h°=263,97
45°
-dL*
+dL*+db*
-db*
+da*-da*
cf = 1.5
-2
-1,5
-1
-0,5
0
0,5
1
1,5
2
-2 -1,5 -1 -0,5 0 0,5 1 1,5 2
-4
-3
-2
-1
0
1
2
3
42
Standard; STANDARD 01
L*=61,62; C*=3,47; h°=263,97
45°
-dL*
+dL*+db*
-db*
+da*-da*
ECMC – Color Difference Formula Summary
• One tolerance for all colors: cf = size of the tolerance ellipse
• Tolerance is based on elliptical spacing
Size and shape of tolerance ellipse is calculated based on Standard location in the color space
0.51245°
Solids
cfcl
ECMC - Typical Tolerances
E00 (CIEDE2000) - Color Difference Formula:2001
• Based on several already existing data sets
• Currently published in the following CIE recommendation:- CIE Technical Report 142: Improvement to industrial colour difference evaluation
• Based on elliptical spacing and L*C*H*
• Corrects for lightness, chroma and hue dependent perception
ECMC – Color Difference Formula Summary
• Better correlation to visual perception:
• Chromatic Colors: Larger visual tolerance ellipse ECMC smaller for chromatic colors than for achromatic colors
(C* and H* are weighted less) compared to E*
• Light Colors: Larger visual tolerance ellipse for lightness ECMC smaller for light colors than for dark colors
(L* is weighted less) compared to E*
• Visual acceptability most sensitive to 1. Hue – 2. Chroma – 3. Lightness (l:c:h = 2:1:1)
E00 - Color Difference Formula
• Difference components L’, C’, H’:
• L’ = L’b - L’s• C’ = C’b - C’s
• where: h’ = h’b - h’s
=
2
'sin''2'
hCCH sb
Weighted color difference part
• Not the regular CIELAB components
L*, C*, H* are used, but the primed
components L’, C’, H’
b = Batch = Sample
s = Standard
= Sample - Standard
=
HHCC
T
HHCCLL SK
H
SK
CR
SK
H
SK
C
SK
LE
'''''222
00
Rotation functionWeighted color difference
E00 - Color Difference Formula
Weighted color difference part
• Improves agreement with visual color
difference perception for neutral colors
• For low chroma colors „G“ increases the
modified a‘ compared to the regular a*
• At higher chroma color a‘ approaches a*
Modification of a* (red-green) axis:
L’= L*
a’ = a* (1 + G)
b’ = b*
22 ''' baC =
=
'
'tan' 1
a
bh
=
77
7
25*
*15.0
ab
ab
C
CG
=
HHCC
T
HHCCLL SK
H
SK
CR
SK
H
SK
C
SK
LE
'''''222
00
E00 - Color Difference Formula
=
HHCC
T
HHCCLL SK
H
SK
CR
SK
H
SK
C
SK
LE
'''''222
00
77
7
25'
'2
=
C
CRC
=
2
25
275'exp30
h
CT RR = 2sin
Rotation function
• Interaction between chroma and hue
difference in blue region (275° ± 25°)
Main influence for high chroma blue
colors
Tilt of major axis of the tolerance
ellipse in the counter-clockwise
directionPhilipp Urban, Mitchell Rosen and Roy Berns: Constructing Euclidean Color
Spaces Based on Color Difference Formulas IS&T/SID Color Imaging Conference,
pp. 77-82, Albuquerque, New Mexico (2007) PDF
E00 - Color Difference Formula
=
HHCC
T
HHCCLL SK
H
SK
CR
SK
H
SK
C
SK
LE
'''''222
00
• Weighting functions to account for
variation in visual color difference
sensitivity dependent on
lightness – chroma - hue
=
2
2
50'20
50'015.01
L
LSL
)('045.01 CSC =
63'4cos20.06'3cos32.0'2cos24.030'cos17.01 = hhhhT
TCSH = '015.01
E00 - Color Difference Formula
=
HHCC
T
HHCCLL SK
H
SK
CR
SK
H
SK
C
SK
LE
'''''222
00
kL = kC = kH = 1 for reference conditions
• Application factors kL, kC, kH to correct for variations in reference conditions:- Illumination: D65- Illumination intensity: 1000 lx- Background field: uniform, neutral grey with L* = 50- Viewing field: > 4°- Sample:
- Homogeneous color without apparent pattern- Direct edge contact between sample and standard- Color difference 1 - 5 CIELAB units
Chroma Circles
colors on the same circle
have the same chroma value
Hue Lines
colors on the same line
have the same hue value
+ b*
90°
+ a*
0°-a*
180°
h°
-b*
270°
CIELAB - System: L*C*h°- Coordinates
Appearance - Gloss
Focus on Reflected Image
Haze Gloss DOI
Image Forming Quality
How is Gloss Perceived?
ObserverIllumination
Smooth Surface
How is Gloss Perceived?
ObserverIllumination
Rough Surface
Glossmeter Design
Defined angles of gloss
20°
85°
60°
Angles of IlluminationSemi GlossLow Gloss High Gloss
0
10
20
30
40
50
60
70
80
90
100
1 2 3 4 5 6 7 8 9 10 11 12 13
85°
60°
20°
Recommended Geometries
Recommended geometryGloss level
Semi gloss
High gloss
Low gloss
60° value
10 to 70 units
> 70 units
< 10 units
60° geometry
20° geometry
85° geometry
Specular Gloss: Dependent on curvature
Specular Gloss:Dependent on coating material
20°
Gloss
Example: 1K versus 2 K
Refractive index
1.541.521.51 1.531.50
80
85
90
95
1 K
2 K
Visual:
Same brilliance
No correlation
Thank you for your attention!
Jeralyn CampBYK Gardner
May 2-3, 2016