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In-house seminar on the how's and why's of color measurement for detergency evaluation
March 3, 2011Prepared by MdMo, SJsm, NBS and TDa
Human color perception, physical phenomena and color coordinates
Instruments for color measurement (in Nz) and associated software
Processing of data from the various instruments – comparisons between the instruments based on real-life sample data
The special problem of UV light and optical brighteners – some real-life sample data
Whiteness measurements/calculations (advanced topic – postponed)
10/04/2023 NOVOZYMES PRESENTATION 2
transmission transmission
UV light (UV = ultraviolet) UV-lys light with a wavelength between 50 and 400 nm (approx)
UV filter UV-filter
value ? lightness, L*
vividness ? see saturation, b*
whiteness hvidhed
Measurable quantities (in principle)
irradiance irradians radiant power per area received at an illuminated surface
radiant energy strålingsenergi
radiant power strålingseffekt radiant energy per time
radiance factor
reflectance, spectral reflectance reflektans ratio of reflected radiant power to incident radiant power
at a certain wavelength
diffuse reflectance
remission remission 'remittance' or the like would have been more consistent terminology
spectral irradiance spektral irradians radiant power, received at a surface, per area and per wavelength interval as a function of wavelength
spectral radiance spektral radians radiant power in the direction of the point from which the source is being observed, per area and per wavelength interval as a function of wavelength
spectral excitance (not exitance) spektral excitans (ikke exitans) total emitted radiant power per area of the radiation source
transmittance transmittans
Measurement process &equipment
aperture (måle)åbning
10/04/2023 NOVOZYMES PRESENTATION 3
Human color perception, physical phenomena and color coordinates
X
Y
Z
R
G
B
x
y
z
L
a
b
L*
a*
b*
r
g
b
10/04/2023 NOVOZYMES PRESENTATION 4
OBJECT
LIGHT SOURCE
OBSERVER / DETECTOR
Observing situation
10/04/2023 NOVOZYMES PRESENTATION 5
Daylight Tungsten Fluorescent
400 500 600 700
Wavelength [nm]
E l D65
400 500 600 700
Wavelength [nm]
E l A
400 500 600 700
Wavelength [nm]
F2E l
LightSource
Illuminant
Light source and illuminant
10/04/2023 NOVOZYMES PRESENTATION 6
Daylight
400 500 600 700
Wavelength [nm]
E l D65
D65 simulates noon daylight in Western/Northern Europe.
Explanation for the D65 nomenclature:
D65: 6500 K (~6503.6 K) = corrected color temperature.
10/04/2023 NOVOZYMES PRESENTATION 7
Incident Light
SpecularReflection
DiffuseReflection
Light interaction with school bus paint
10/04/2023 NOVOZYMES PRESENTATION 8
RED GREEN
BLUE
TEST LIGHT
EYE
BLACK PARTITION
TEST FILTER
2º / 10º
Determination of standard colorimetric observer
10/04/2023 NOVOZYMES PRESENTATION 9
Color matching functions
CIE RGB color matching functions
For most test colors:
T = αr + βg + γb
For some test colors:
T + αr = βg + γb ↕T = βg + γb - αr
RGB tristimulus values
10/04/2023 NOVOZYMES PRESENTATION 10
CIE XYZ color matching functions
XYZ tristimulus values
10/04/2023 NOVOZYMES PRESENTATION 11
=
CIE y Observer
CIE x Observer
CIE z Observer
x
x
x =
=
=
CIE X Tristimulus
X = 41.9CIE Y Tristimulus
Y = 37.7CIE Z Tristimulus
Z = 8.6
x
Visual Stimulus
CIE Illuminant D65
Reflectance
Calculation of tristimulus valuesTristimulus
values
10/04/2023 NOVOZYMES PRESENTATION 12
Tristimulus values expressed mathematically
These values may be what somebody means, if they talk about ”RGB” values or ”XYZ” values.
Visual Stimulus CIE y ObserverCIE Y Tristimulus
* =
10/04/2023 NOVOZYMES PRESENTATION 13
This may also be what somebody means, if they talk about ”xyz” values.
Chromaticity coordinates
XYZ: No good visual correlation
Y is ”understandable”: Lightness
Chromaticity coordinates
10/04/2023 NOVOZYMES PRESENTATION 14
RGB chromaticity coordinates also exist:
This may also be what somebody means, if they talk about ”rg” values.
10/04/2023 NOVOZYMES PRESENTATION 15
RGB color space: All possible colors that can be made from a set of red, green and blue.
It is a “sub-space” - only a selection of colors can be made just by mixing red, green and blue.
RGB color space
10/04/2023 NOVOZYMES PRESENTATION 16
Colors in an RGB color space are often displayed in a color cube in a 3D coordinate system
Coordinates in this space may also be what somebody means, if they talk about ”rgb” values.
Black = (0, 0, 0)White = (1, 1, 1) or (255, 255, 255)
Red = (1, 0, 0) or (255, 0, 0)Green = (0, 1, 0) or (0, 255, 0)Blue = (0, 0, 1) or (0, 0, 255)
10/04/2023 NOVOZYMES PRESENTATION 17
Calculating L*, a* and b*
With X, Y and Z, it is possible to calculate L, a, b and L*, a*, b*, which are coordinatesin two different 3D color spaces.
(Be aware!: Both set of coordinates are commonly referred to as ”L, a, b”).
a axis: green / red
b axis: blue / yellow
L axis: dark / light
10/04/2023 NOVOZYMES PRESENTATION 18
E.g., if X/Xn, Y/Yn, and Z/Zn are all greater than 0.008856, then:
L* = 116 (Y / Yn)1/3 − 16
a* = 500((X/Xn)1/3 − (Y/Yn)1/3)
b* = 200((Y/Yn)1/3 − (Z/Zn)1/3)
Xn, Yn, and Zn are the tristimulus values for the illuminant.
Yn = 100.00 CIE 10° Standard Observer Illuminant Xn Zn
A 111.16 35.19 D65 94.83 107.38 F2 102.13 69.37
10/04/2023 NOVOZYMES PRESENTATION 19
L, a, b vs L*, a*, b*
L*, a*, b* give the best possible uniformity across color space.
- These are the standard coordinates used today.
10/04/2023 NOVOZYMES PRESENTATION 20© 2001 HunterLab© 2001 HunterLab
Reduction to one number – quantifying color difference in 3D
ΔE* = (ΔL*2+ Δa*2 + Δb*2)1/2
10/04/2023 NOVOZYMES PRESENTATION 21
Human color perception, physical phenomena and color coordinates
X
Y
Z
R
G
B
x
y
z
L
a
b
L*
a*
b*
r
g
b
10/04/2023 NOVOZYMES PRESENTATION 23
Color Eye 7000
Color Eye 7000
• Pulsed xenon light source• Measuring geometry d/8• Two spectral analyzers• Spectral range 360 nm to 750 nm (??)• Reflection registered at every 10 nm (??)• Calibration (according to message from Largo in 1996):
– 6 ceramic tiles calibrated by Macbeth in the US against a tile set traceable to NIST (National Institute of Standards and Technology)
– Tolerances 0.3 ΔE CMC 1:1 (white, medium gray, gray) and 0.5 ΔE CMC 1:1 (yellow, green, cyan)
– Daily calibration on black and white standards, control with green tile
Ture Damhus •
The Tidas robots
Tidas 1 & 2Tidas = Transputer-Integrierte Dioden-Array-Spektrometer
MCS 521 VIS diode-array spectrophotometers from Zeiss (340-1000 nm)
Tidas 1
CLX 75 W xenon lamp
measuring unit OFR 90 with integrating sphere
Tidas 2
measuring unit OMK 500-H (380-900 nm)
with SVS CLH 500 halogen lamp (360-2400 nm)- measuring geometry 0/45 (15 individual optical fibersin 15×24 arrangement, double beam to spectrophotometer)- this measuring unit is recommended for textured samples
Lamps
• Deuterium 190-620 nm• Halogen 360-2400 nm• Xenon 280-900 nm• Xenon flash 220-900 nm
[Taken from Zeiss MCS 500 spectrophotometer brochure]
Konica-Minolta spectrophotometer CM-3610d
10/04/2023 NOVOZYMES PRESENTATION 29
Konica-Minolta spectrophotometer CM-3610d
• 4 pulsed xenon lamps• Numerical gloss control for excluding/including specular
component• Numerical UV control with filter cut-off at 400 nm or 420 nm• Dual channel sensor (photodiode arrays) arrangement • Spectral range 360 nm to 740 nm (??)• Reflection registered at every 10 nm (??)• Measuring geometry d/8
Scanner technology – Kodak iQsmart
• Light source: cold cathode lamp• Sensor: CCD (Charge-coupled device) moving
across the stain(s)• Output: r, g, b values
Setup when scanning
Resolution of the output-image (in dots per inch)
Number of colors that the image will be able to show (RGB16 enables 281,474,976,710,656 colors – because 216 x 216 x 216 = 281*1012 )
Sharpness function compensates for loss insharpness during ”scanning and printing”
Red\Green\Blue
10/04/2023 NOVOZYMES PRESENTATION 33
Using our ”Color Analyzer” software for the scanner, the image data is reduced to coordinates in the rgb-space. This is then further reduced into ”intensity”, which is
Black = (0, 0, 0)White = (1, 1, 1) or (255, 255, 255)
Red = (1, 0, 0) or (255, 0, 0)Green = (0, 1, 0) or (0, 255, 0)Blue = (0, 0, 1) or (0, 0, 255)
222 bgr
Camera technology – the DigiEye (Nikon D90)
• Light sources: Fluorescent lamps & LED• Sensor: CMOS (Complementary metal–oxide–semiconductor)
• Output: r, g, b values
Cross-section view of system:1. 4-element lens2. Reflex mirror3. Focal-plane shutter4. Image sensor5. Matte focusing screen6. Condenser lens7. Pentaprism8. Eyepiece
Color theory and measurements in the lab.
5 colorful stains are measured one by one with a white
background.
Measurement equipment:Coloreye
(Specular excluded, No UV).
Influence of the background
Gravy Blueberry jam EMPA116Rubbed grass CS-28
10/04/2023 NOVOZYMES PRESENTATION 39OBJECT
LIGHT SOURCE
OBSERVER
Visual observing situation
10/04/2023 NOVOZYMES PRESENTATION 40
=
CIE y Observer
CIE x Observer
CIE z Observer
x
x
x =
=
=
CIE X Tristimulus
X = 41.9CIE Y Tristimulus
Y = 37.7CIE Z Tristimulus
Z = 8.6
x
Visual Stimulus
CIE Illuminant D65
Reflectance
Calculation of tristimulus values
Tristimulusvalues
Gravy Blueberry jam
EMPA116Rubbed grassCS-28
L* (D65) a* (D65) b* (D65)063KC gravy 70 12 27
Hartleys Blueberry jam 55 22 -2EMPA 116 43 2 5
Rubbed grass 52 3 27CS-28 80 39 51
Paremeters: Color eye, no UV, specular excluded.Data calculations: D65, 10° observer
Why measure at 460 nm?
• Does measuring at 460 nm give an indication of how white the stain is?
• At which wavelength do we have the largest delta value, and hence the biggest window?
• Does the delta reflectance value at 460 nm correspond with the visual stain.
• Historical reasons?
Test conditions.
Stain name Suplier FabricCS-28 CFT cotton
EMPA 116 EMPA cotton063KC gravy Equest Cotton
123KC Tomato Puree Equest Cotton122KC Ketchup Equest Cotton
013bKC Overripe Banana Equest CottonHartleys Blueberry jam Equest Cotton
004KC Chocolate Pudding Equest CottonBlack tea Equest Cotton
Blackberry whole fruit Equest PolyesterBlod Equest Cotton
Rubbed grass Equest CottonGrass liquid Equest PolyesterTangerine Equest Cotton
Red wine (EMPA122) EMPA Cotton
1 2 3No wash Washed with
water Washed with
detergent (+enzymes)
Wash conditions:EU fullscale wash, 30 °C, tap water. Detergent: 37 g/wash Ariel Excel Gel Colour (contains optical brighteners)
Data collection:DigiEyeColor eye Conica Minolta(Photo)
CS-28
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
Washed with de-tergent, No UV
Washed with water, No UV
Not washed, No UV
% R
eflec
tanc
e
EMPA116
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
5.00
10.00
15.00
20.00
25.00
30.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Gravy
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Tomato Puree
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Ketchup
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 700-5.00
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no washDe
lta re
flecti
on
Overripe Banana
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 700
-5.00
0.00
5.00
10.00
15.00
20.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no washDe
lta re
flecti
on
Chocolate pudding
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Blood
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Blueberry jam
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Blackberry Whole fruit
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Red wine
No wash Washed with water Washed with detergent
Compared to white fabric
L* (D65) a* (D65) b* (D65) ΔE(D65)Washed with detergent 82,3 4,6 6,0 15,6Washed with water 78,6 5,1 6,8 19,3Not washed 72,3 16,6 9,6 30,8
420 460 500 540 580 620 660 700
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
25.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no washDe
lta re
flecti
on
Black tea
No wash Washed with water Washed with detergent
Compared to white fabric
L* (D65) a* (D65) b* (D65) ΔE(D65)Washed with detergent 78,9 8,2 19,3 26,9Washed with water 75,1 8,9 21,3 31,0Not washed 77,6 12,0 28,4 35,8
420 460 500 540 580 620 660 700
-10.00
-5.00
0.00
5.00
10.00
15.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no washDe
lta re
flecti
on
Rubbed grass
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
5.00
10.00
15.00
20.00
25.00
30.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Grass liquid
No wash Washed with water Washed with detergent
420 460 500 540 580 620 660 7000.00
5.00
10.00
15.00
20.00
25.00
30.00
Measured on Color eye, no UV, specular excluded
Washed with de-tergent− no wash
Washed with wa-ter− no wash
Delta
refle
ction
Dosis response curves and measuring instrument comparison.
Instrument settings: No UV
CS-28, dosis response
420 440 460 480 500 520 540 560 580 600 620 6400.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
Minolta - CS-28, no washMinolta - CS-28,wash 0,03mg EP/L StainzymeMinolta - CS-28,wash 0,06mg EP/L StainzymeMinolta - CS-28,wash 0,12mg EP/L StainzymeMinolta - CS-28,wash 0,20mg EP/L StainzymeMinolta - CS-28,wash 1,00mg EP/L StainzymeMinolta - CS-28,wash no enzMinolta - WFK 10A
% R
eflec
tanc
e
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 125.0
30.0
35.0
40.0
45.0
50.0
Color eye 2Color eye 3MinoltaTidas
mg EP/L (Stainzyme)
Refle
ctan
ce 4
60nm
Comparing measurements at 460nm
10/04/2023 NOVOZYMES PRESENTATION 62
400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 7000
10
20
30
40
50
60
70
80
90
063KC gravy , Wash, Minolta, No UV(420nm cut)
063KC gravy , Wash, DigiEye, No UV
063KC gravy , Wash, Color eye no. 2, No UV
063KC gravy , No wash, DigiEye, No UV
063KC gravy , No wash, Color eye no. 2, No UV
063KC gravy , No wash, Minolta, No UV(420nm cut)
%Re
flect
ance
10/04/2023 NOVOZYMES PRESENTATION 63
400 420 440 460 480 500 520 540 560 580 600 620 640 660 680 7000
10
20
30
40
50
60
70
80
90
Blod, Wash, DigiEye, No UV
Blod, Wash, Color eye no. 2, No UV
Blod, Wash, Minolta, No UV(420nm cut)
Blod, No wash, DigiEye, No UV
Blod, No wash, Color eye no. 2, No UV
Blod, No wash, Minolta, No UV(420nm cut)
% R
elfe
ctan
ce
Optical brighteners and measuring with UV light from light source included (i.e., with no UV filter).
Common fluorescent whitening agents (FWA) (=optical brighteners, OB) in laundry detergents
These substances are substantive towards cotton, but do not adsorb significantly to polyester
• A DSBP
(distyrylbiphenyl-type) FWA
(Tinopal CBS ex BASF)
• A DAS
(diaminostilbene-type) FWA
Blueing agents vs. FWA
Upper graph: remission of white fabric (a) with blueing agent added
(b low level, c high level)
Lower graph: remission of white fabric (a) with FWA added
(b low level, c high level)
Swatches washed in a detergent without FWA uw = unwashed; w = washed
Data provided by MLsd
400 500 600 7000
20
40
60
80
100
120
Remission without UV
EMPA164 wCS-28 wCS-61 wwfk10A wEMPA164 uwCS-28 uwCS-61 uwwfk10A uw
nm
Rem
issio
n
Swatches washed in a detergent without FWA uw = unwashed; w = washed
Data provided by MLsd
400 500 600 7000
20
40
60
80
100
120
Remission with UV
EMPA164 wCS-28 wCS-61 wwfk10A wEMPA164 uwCS-28 uwCS-61 uwwfk10A uw
nm
Rem
issio
n
Light source: D65
Photos of detergent in a light cabinet (recorded with a digital camera)
Light source: only UV
Equest stain, bistro gravy on cotton.Photos from light cabinet in D65 and UV light.
not washed Washed with water Wash with detergent not washed Washed with water Wash with detergent
420 520 6200
10
20
30
40
50
60
70
80
90
Washed with detergent, No UV(420nm cut)
Washed with wa-ter, No UV(420nm cut)
Not washed, No UV(420nm cut)
Refle
ctan
ce
420 520 6200
10
20
30
40
50
60
70
80
90
Washed with de-tergent, 100% UV
Washed with water, 100% UV
Not washed, 100% UV
Rem
issio
n
Konica Minolta, with UV filter(420 nm cut), measurement on the stain.
Konica Minolta, with no UV filter,measurement on the stain.
Light source in photo: D65 Light source in photo: only UV
063KC-Bistro gravy on cotton
not washed Washed with water Wash with detergent
420 460 500 540 580 620 660 7000
2
4
6
8
10
12
14
16
18
20
UV contribution to remission, Konica Minolta, measurement on stain.
Washed with detergent, (100% UV-No UV)
Washed with water, (100% UV-No UV)
Not washed, (100% UV-No UV)
Delta
rem
issio
n
Light source in photo: only UV
Equest stain, CS-28 on cotton.Photos from light cabinet in D65 and UV light.
not washed Washed with water Wash with detergent not washed Washed with water Wash with detergent
420 520 6200
10
20
30
40
50
60
70
80
90
100
Washed with detergent, 100% UV
Washed with water, 100% UV
Not washed , 100% UV
Rem
issio
n
Light source in photo: D65 Light source in photo: only UV
Konica Minolta, with UV filter(420 nm cut), measurement on the stain.
Konica Minolta, with no UV filter,measurement on the stain.
420 520 6200
102030405060708090
100
Washed with de-tergent, No UV(420nm cut)
Washed with water, No UV(420nm cut)
Not washed, No UV(420nm cut)
Refle
ctan
ce
CS-28, Rice starch on cotton
420 460 500 540 580 620 660 7000
2
4
6
8
10
12
UV contribution to remission, Konica Minolta, mea-surement on the stain.
Washed with de-tergent, (100% UV-No UV)
Washed with water, (100% UV-No UV)
Not washed, (100% UV-No UV)
Delta
rem
issio
n
Light source in photo: only UV
Equest stain, Grass liquid on polyester.Photos from light cabinet in D65 and UV light.
not washed Washed with water Wash with detergent not washed Washed with water Wash with detergent
420 520 6200
102030405060708090
100
Washed with de-tergent, 100% UV
Not washed, 100% UV
Washed with water, 100% UV
Rem
issio
n
Light source in photo: D65 Light source in photo: only UV
Konica Minolta, with UV filter (420 nm cut), measurement on the stain.
Konica Minolta, with no UV filter,measurement on the stain.
420 520 6200
102030405060708090
100
Washed with detergent, No UV(420nm cut)
Washed with wa-ter, No UV(420nm cut)
Not washed, No UV(420nm cut)
Refle
ctan
ce
Grass liquid on polyester
420 460 500 540 580 620 660 7000123456789
10
UV contribution to remission
Washed with detergent, (100% UV-No UV)
Washed with water, (100% UV-No UV)
Not washed, (100% UV-No UV)
Delta
rem
issio
n
Light source in photo: only UV
