THE INFLUENCE OF PARAMETRIC EFFECTS ON THE APPEARANCE OF SMALL COLOUR ...

199 Pages·2012·8.98 MB·English

CLOTHWORKERS'
LIBRARY
UNIVERSITY
OF LEEDS
THE INFLUENCE OF PARAMETRIC EFFECTS ON THE
OF SMALL COLOUR DIFFERENCES
APPEARANCE
by
Kim
Dong-Ho
for degree
Submitted in the
the of
accordance with requirements
Doctor Philosophy
of
The University Leeds
of
Department Colour Chemistry Dyeing
of and
April 1997
I REFERENCE
The is his
candidate confirms that the work submitted own and that appropriate
has been has been
credit given where reference made to the work of others.
BORROWED
BE
TO
NOT
MARK/
CLASS
NUMBER
BOOK
L/aT2%11
ABSTRACT
The the two background
effects of physical parameters, and gap, on the perception of small
differences (AE* < 5) investigated by 248 21
colour were use of colour-difference pairs around
from Each by 30
colour centres made painted samples. pair was assessed an average of times
under each viewing condition using a grey-scale method and/or a paired-comparison method.
From the data, (ellipses) determined by
visual colour-difference ellipsoids or tolerances were use
logistic
by least-square
of a or a probit maximum-likelihood analysis model, or a method.
The perceived tolerance sizes along the three colour-difference directions AL*, OC1 and AH` in
the CIELAB space were found to be little influenced by a change of lightness of the grey
background but influenced (i. decrease in by 0.51' between
tolerance
significantly e., size) a gap a
The factor for lightness for
pair of samples. gap the component was greater than that chroma or
hue both latter having This be for
components, the similar magnitudes. could an explanation the
increase lightness I (or factor KL) by factor 2 in
the tolerance the three
of relative parametric a of
CIELAB formulae (CMC, BFD CIE94) for judgements, in
modified and acceptability which
having dividing line between In
textile them, the
samples, an unclear are mainly used. addition,
Q is be between lightness
the tolerance thought to the the
value of relative used practically ratio
tolerances.
and chroma
The from The
experimental uncertainties non-physical parameters were also quantified.
degrees (i. judgements
of precision e., standard error) of colour measurements and observer were
found to be (±4% ±7%, The different data
good and respectively). methods of scaling and
found have little impact
to the
analysis were on results.
The lightness, hue in
chroma and tolerances with respect to the standard colour position the
CIELAB in detail datasets from
space were studied using the various existing and the set this
The lightness dependency lightness for
study. tolerance showed a clear upon the metric medium
to light but in the dark there discrepancy between datasets.
colours, case of colours was a the
Both the hue tolerances dependency both hue-angle
chroma and showed upon the chroma and
dependency
and not the single upon the metric chroma, as assumed in the CIE94 formula.
New functions derived from
the finally
weighting were above experimental evidence, and a
formula, LCD (Leeds Colour Difference)
The LCD formula is
new was proposed. nearly as
flexible CIE94 but individual
simple and as smoothes the functions to CMC
weighting compared
BFD, for lightness tolerances for light discrimination
and especially
colours and chromaticity
blue It found
near the region. was also that the reliability of the BFD formula is improved when
the size of the chroma weighting function is increased by 1.5 times the form lightness
and of
function is
weighting made parallel to those the CIELAB formulae.
of other modified
I dedicate late father.
this thesis to
my mother and
Acknowledgments
The Dr. J. H. Nobbs for his during
thanks this
author supervision and advice
research.
I for
to
am also grateful all observers willingly conducting visual assessments
and the former and present Korean colleagues in the department for their help
and assistance.
My special thanks go to Mr. C. Yoon and Mr. K. Suragul for their intensive
Dr. K. Sunwoo for helping
observing sessions, me adapt to new circumstances
Jeff Pitchford for booth frame
background.
and
making of viewing and
Finally, family for
thanks to all members of my their love,
continuing support
Ms. I. Kim for her friendship
and encouragement and to love.
and
iv
Table Contents
of
1. INTRODUCTION
1
...........................................................................................
1.1 Colour Specification Systems
1
.........................................................................
1.1.1 Colour
1
order system
.........................................................................................
1.1.1.1 Munsell 2
system
...............................................................................................
1.1.1.2 Natural (NCS) 2
colour system
...........................................................................
1.1.2 CIE
4
system
........................................................................................................
1.1.2.1 CIE 5
tristimulus
values
......................................................................................
1.1.2.2 CIE Standard Observers (colour functions) 7
matching
.......................................
1.1.2.3 CIE Standard Illuminants Sources 7
and
.............................................................
1.1.2.4 CIE / illumination 8
standard viewing conditions
.................................................
1.1.2.5 CIE diagrams 10
chromaticity
............................................................................
1.2 Colour Appearance Phenomena
11
..................................................................
1.2.1 Colour 12
constancy
............................................................................................
1.2.2 Achromatic induction 12
and chromatic
...............................................
1.2.3 Chromatic
14
adaptation
....................................................................................
1.2.4 Metamerism
15
...................................................................................................
1.3 Colour-Difference Fonnulae
16
.........................................................................
1.3.1
Formulae based Munsell
the 17
on system
.......................................................
1.3.1.1 CIELAB
17
........................................................................................................
1.3.2 Formulae
based
the
on empirical approach 20
..................................................
1.3.2.1 CIELUV
20
........................................................................................................
1.3.3 Formulae based
on the theoretical approach 21
................................................
1.3.3.1 FMC
22
..............................................................................................................
1.3.4 Advanced formulae
colour-difference 23
.............. ........................................ ...
1.3.4.1 CMC, BFD CIE94
23
and
..................................................................................
1.3.4.2 DCI-95
25
..........................................................................................................
1.3.4.3 LLAB
26
............................................................................................................
V
1.4 Quantifying Visual Colour Difference
27
........................................................
1.4.1 General introduction
27
...................................................................................
..
1.4.1.1 Types
of scales 27
............................................................................................
..
1.4.1.2 Psychophysical
methods 28
...............................................................................
..
1.4.1.3 Weber's law
28
................................................................................................
..
1.4.1.4 Representation data
of 29
................................................................................
..
1.4.2 Scaling
methods 30
...........................................................................................
..
1.4.2.1 Ranking
method 30
..........................................................................................
..
1.4.2.2 Paired-comparison
30
method
.......................................................................... ..
1.4.2.3 Category
32
method
.........................................................................................
..
1.4.2.4 Ratio
method 33
..............................................................................................
..
1.4.2.5 Grey-scale
34
method
.......................................................................................
..
1.5 Thesis Aims
35
....................................................................................................
..
1.6 References
36
.......................................................................................................
2. THEORY
40
..........................................................................................................
2.1 Analysis Visual Data
of 40
................................................................................
2.1.1
Maximum-likelihood
method 40
........................................................................
2.1.1.1
Logistic function
41
...........................................................................................
2.1.1.2
Probit
analysis 43
................................................................................................
2.1.1.3 Sampling
44
......................................................................................................
2.1.2 Least-square
method 46
......................................................................................
2.2 Visualisation
Ellipsoid
the
of
47
........................................................................
2.2.1 Calculation
of principal axes
..............................................
2.2.2 Ellipsoid
tilting
50
..............................................................................................
2.2.3 Ellipse
parameters 50
..........................................................................................
2.2.4 Ellipsoid (ellipse)
transform
52
.........................................................................
vi
2.3 Measures Fit
of 54
................................................................................................
2.4 Errors in Colour Measurement
56
....................................................................
2.5 Observer Assessments
58
..................................................................................
2.5.1 Colour discrimination
tests
59
...........................................................................
2.5.1.1 Farnworth-Munsell
100 Hue Test
59
.................................................................
2.5.1.2 Triangle Test
59
................................................................................................
2.5.1.3 HVC (Hue, Value, Chroma) Color Vision Skill Test
and 59
...............................
2.5.2 Observer
uncertainty 60
....................................................................................
2.5.2.1 Precision
of visual results 61
..............................................................................
2.5.2.2 Observer
variability 62
........................................................................................
2.6 Physical Parameters
63
........................................................................................
2.6.1 Gap
effect 64
......................................................................................................
2.6.2 Background
effect 65
..........................................................................................
2.6.3 Other
effects 66
..................................................................................................
2.7 References
67
.......................................................................................................
3. EXPERIMENTAL
70
........................................................................................
3.1
General
70
......... .....................................................................................................
3.2 Sampling
70
..........................................................................................................
3.2.1 Part
data
one
analysis methodology 70
-
.....................
.....................................
3.2.2 Part
two lightness
study tolerances
of 71
-
.....................
..................................
3.2.3 Part
three hue dependence
study
of angle 72
..................................................
3.2.4 Standard
pairs
74
...................................................
..............................................
3.2.5 Grey
scale
74
......................................................................................................
3.3 Sample Preparation
75
........................................................................................
3.4 Colour Measurements
76
...................................................................................
vii
77
3.5 Visual Assessments
......... ...............................................................................
77
3.5.1 Viewing
conditions
.......................................................................................
78
3.5.2 Observer judgements
......................................................................................
80
3.5.2.1 Paired-comparison
method
............................................................................
80
3.5.2.2 Grey-scale
method
.........................................................................................
80
3.6 Software Packages
.........................................................................................
81
3.7 References
.......................................................................................................
4. RESULTS AND DISCUSSION
PART I-5 CIE COLOUR CENTRES 82
.................................................
82
4.1 Red Centre
.......................................................................................................
90
4.2 Grey Centre
.....................................................................................................
94
4.3 Blue Centre
'
.... ..................................................................................................
98
Green Centres
4.4 Yellow
and
............................................................................
98
4.5 Comparison Previous Studies
with
..............................................................
formulae 99
4.5.1 Overall fit
of colour-difference
.....................................................
101
4.5.2 Principal
tilting parameters
and ellipse
axes,
..............................................
4.6 References 103
......................................................................................................
5. RESULTS AND DISCUSSION
EFFECTS
PART 11 PARAMETRIC 104
-
..................................................
Parameters Background Gap 104
5.1 Physical
and
-
............................................
104
lightness difference
5.1.1 Effects
on
....................................................................
104
differences
5.1.1.1 Lightness
under standard condition
.............................................
viii
112
5.1.1.2 Lightness differences
under parametric condition
.........................................
factors for lightness difference 115
5.1.1.3 Parametric
correction
...................................
5.1.2 Effects discrimination 117
on chromaticity
........................................................
5.1.2.1 Chromaticity discrimination 117
under standard condition
...................................
5.1.2.1.1 Chroma dependence hue differences 119
of chroma and
....................................
5.1.2.1.2 Hue dependence hue differences 124
of chroma and
........................................
5.1.2.2 Chromaticity discrimination 132
under parametric condition
................................
5.1.2.3 Parametric factors for hue differences 132
correction chroma and
........................
5.1.3 Effects discrimination 3 CIE 134
on colour around colour centres
..................
5.2 Colour Measurement Error 136
...........................................................................
5.3 Observer Uncertainty 139
....................................................................................
5.4 References 142
......................................................................................................
6. NEW WEIGHTING FUNCTIONS FOR THE MODIFIED
CIELAB COLOUR-DIFFERENCE FORMULA 144
.............................
6.1 Specification New Weighting Functions 144
of
...............................................
6.1.1 Lightness function 145
weighting
......................................................................
6.1.2 Chroma hue functions 146
and weighting
.........................................................
6.1.3 Ellipse function 146
rotation
...............................................................................
6.1.4 Modification BFD functions 148
the
of weighting
...........................................
6.2 Test New Weighting Functions
149
of
...............................................................
6.3 LCD New Weighted CIELAB Formula 155
-
.......................... .......................
6.4 References
157
......................................................................................................
7. CONCLUSIONS
158
..........................................................................................
ix
APPENDICES
164
....................................................................................................
A. 1 Experimental data
164
........................................................................................
A. 2 Ellipsoid (ellipse) for 3 CIE
coefficients and parameters centres
for for lightness difference
tolerance the
and vectors red and of
11
centres 175
.....................................................................................................
A. 3 Coefficients 180
and parameters of chromaticity ellipses 182
.....................
formula
A. 4 BFD(i: 184
c) colour-difference
........................................................
X
List Figures
of
3
Figure 1-1. Schematic diagram of the Munsell colour solid
...........................................
(W) black (S) (R)
Figure 1-2. Arrangement of colours on a white red plane
- -
3
NCS
the
of
............................................................................................................
Figure 1-3. CIE tristimulus functions: (a) r, g, b for colour matching
spectral
(b)
lights 435.8,546.1 700.0
with monochromatic of and nm, and xx, yx, za,
6
imaginary
for
colour matching with primaries
........................................................
Figure 1-4. Spectral distributions CIE Illuminants A, B, C, D65 9
energy of
....................
Figure 1-5. CIE illumination
recommended and viewing conditions
9
for
reflectance measurements
..................................................................................
11
Figure 1-6. CIE 1931 diagram
chromaticity
................................................................
in
field
Figure 1-7. Examples
of visual configuration used
13
induction
(a) induction (b)
and chromatic
achromatic
............................................
diagram for D65 (solid dots)
Figure 1-8. Colour adaptation
appearance
15
for A (open triangles)
and adaptation
Figure 1-9. Reflectance curves of a target and an attempted match
16
showing metamerism
...........................................................................................
21
Figure 1-10. CIELUV
colour space
............................................................................
CIE diagram 22
Figure 1-11. MacAdam ellipses plotted on a chromaticity
.......................
27
Figure 1-12. Various
measurement scales
...................................................................
data interval 31
Figure 1-13. Transformation to
an scale
of visual
....................................
Figure 2-1. Distribution
of observer responses:
(a) Gaussian function (cummulative (b) logistic function 42
normal), and
...................
Figure 2-2. Depiction of filtering algorithm applied to nonmonotonic
45
observer responses
............................................................................................
49
Figure 2-3. Three dimensional
polar co-ordinates
........................................................
a 53
Figure 2-4. Chromaticity-discrimination in b* diagram
ellipse
...................................