optical blending: a comparison of spectrophotometric

OPTICAL BLENDING: A COMPARISON OF SPECTROPHOTOMETRIC

MEASUREMENTS AND HUMAN VISUAL ASSESSMENTS

OF BLENDED COLOR BLOCKS

By

CAROL P. DAHMS

Under the Direction of Helen Epps

ABSTRACT

This study makes comparisons about optical blending by using woven samples, known

colors. Samples were prepared and instrumental color measurements were taken on those

samples. Human visual assessments of the samples were gathered and compared to the

instrumental measurements.

INDEX WORDS: Optical blending, Color, Natural Colour System, Woven




By

CAROL P. DAHMS

B.S., Charleston Southern University, 1973

A Thesis Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment

of the Requirements for the Degree

MASTER OF SCIENCE

ATHENS, GEORGIA

2007

i

2007

Carol P. Dahms

All Rights Reserved




by

CAROL P. DAHMS

Major Professor: Helen Epps

Committee: Patricia Annis Patricia Hunt-Hurst

Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia August 2007

iii

ACKNOWLEDGEMENTS

My thanks go to the following individuals for their assistance. Of course, to Dr. Helen Epps, who

made this step on the degree process easier by her willingness to give support and advice. To the

other committee members, Dr. Patricia Annis, Dr. Patricia Hunt-Hurst and Glen Kaufman,

Lamar Dodd School of Art, my thanks for your participation and comments. Thanks also go to

Jenny and Annette at Jacquard Products, Inc. for help with information about the dyes, and the

staff at the Yarn Barn of Kansas. For allowing me to recruit subjects from their classes, thanks

are extended to Dr. Diann Moorman, Dr. Arthur Grider, Ms. Emily Blalock, and Dr. Jan

Hathcote. I also thank the other TXMI faculty and my fellow students for their moral support.

iv

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS........................................................................................................... iv

TABLE OF CONTENTS.................................................................................................................v

LIST OF TABLES........................................................................................................................ vii

LIST OF FIGURES ..................................................................................................................... viii

CHAPTER

1 INTRODUCTION .........................................................................................................1

2 REVIEW OF LITERATURE ........................................................................................3

Color Vision Theories ...............................................................................................3

Color Vision ..............................................................................................................3

Optical Blending........................................................................................................4

Instrumental Color Measurement ..............................................................................7

Natural Colour System ..............................................................................................8

3 METHODS AND PROCEDURES .............................................................................10

Preparation of Samples............................................................................................10

Instrumental Measurements of Blended Color Blocks............................................11

Card Selection Process ............................................................................................12

Human Visual Assessments ....................................................................................14

4 RESULTS ....................................................................................................................17

Analysis of Cards Chosen .......................................................................................17

Analysis of Target Card Elimination.......................................................................22

5 SUMMARY AND RECOMMENDATIONS..............................................................26

v

Analysis of Cards Chosen .......................................................................................26

Analysis of Target Card Elimination.......................................................................28

Recommendations ...................................................................................................28

REFERENCES ..............................................................................................................................30

APPENDICES ...............................................................................................................................32

A Dyes from Jacquard Products ......................................................................................32

B CIE L*a*b* Measurements of Cards Used for Assessments.......................................33

C Comparisons of Blended Color Blocks, Target and Chosen Cards .............................36

D Sample of Recording Sheet..........................................................................................37

vi

LIST OF TABLES

Page

Table 3.1: Card Description and Corresponding Code Numbers ..................................................12

Table 4.1: Number of Times Participants Chose Cards.................................................................18

Table 4.2: Summary of Number of Times Each Card Was Chosen ..............................................19

Table 4.3: Overall Analysis of Card Choices ................................................................................19

Table 4.4: Card Choices by Blended Color Block.........................................................................20

Table 4.5: Elimination of Target Card...........................................................................................23

vii

LIST OF FIGURES

Page

Figure 1.1: Color Blanket Use in Pilot Study ..................................................................................1

Figure 2.1: Georges Seurat’s A Sunday on the La Grande Jatte .....................................................6

Figure 2.2: NCS Colour Space ........................................................................................................8

Figure 2.3: NCS Colour Wheel........................................................................................................8

Figure 2.4: NCS Colour Triangle.....................................................................................................9

Figure 2.5: NCS Notation Description.............................................................................................9

Figure 3.1: Blended Color Blocks Used for Visual Assessments..................................................11

Figure 3.2: Cards Used for Visual Assessments............................................................................13

Figure 3.3: Sample of Card Arrangement Used for Visual Assessments ......................................15

viii

CHAPTER ONE

INTRODUCTION The purpose of this research was to study optical blending by comparing instrumental

color measurements with visual assessments of woven color blocks consisting of known blends

of colored yarn. It is known that human visual assessments and instrumental color

measurements often do not agree. Optical blending further complicates this issue.

The first objective was to analyze the cards that participants chose and how often they

chose those cards. A second objective was to determine at what point in the viewing process the

designated target card was eliminated. For purposes of this study, a standard size of juxtaposed

colors and constant viewing distance were used thereby eliminating any variability that a change

in these two conditions might cause. The methodology used in the pilot study was used in this

study with only slight variation.

Figure 1.1 Color Blanket Used in Pilot Study

1

Previous to this research, a pilot study was conducted using an existing wool color

blanket on which instrumental color measurements were taken. The blanket consisted of thirty

colors in one and one-half inch stripes in the warp direction. The same thirty colors were woven

in as filling/weft in the same color order as in the warp, creating intersecting blocks of all of the

colors with each of the other colors. A photograph of the blanket appears in Figure 1.1. Each of

the solid color blocks and each of the blended color blocks were measured on a

spectrophotometer to determine whether or not a relationship existed between the color

measurement of a specific blended block and the average of the two solids colors that were used

to form it. Evidence was found 1) that a relationship did exist between the blended blocks and

the two solid colors used to form it and 2) that this relationship was approximately equal.

2

CHAPTER TWO

REVIEW OF LITERATURE

In order to achieve the stated objectives, the researcher needed to be familiar with the

areas of color vision, theories about color vision, optical blending, instrumental color

measurement, the Natural Colour System and other work performed in these areas. A review of

the existing literature was conducted.

Color Vision Theories

Many theories about how color vision works have been postulated. Important among

those are the works of Thomas Young and Hermann Helmholtz along with that of Ewald Hering.

In 1802, Young postulated what is often referred to as the trichromatic theory. It stated that there

are three different kinds of color receptors in the eye. Each of those receptors has a different

spectral sensitivity. His work was refined by Herman Helmholtz in the 1850s. These two

scientists based their theories on the observation that any color in the visible spectrum can be

matched by mixing three basic colors of light in different proportions.5

Another equally important theory was that of Ewald Hering in 1878. Referred to as the

opponent process theory, it postulated that there were two different groups of cells that

controlled color and a third group that controlled brightness. His theory was based on two

primary factors. One, that blue and yellow could not exist together in the same color nor could

red or green. Secondly, he observed that the afterimage of each color existed and that it was

these opposing colors; red afterimages to green, green to red, yellow to blue, and blue to yellow.

Subsequent research has shown that both theories were correct and that our color vision is a

complex combination of both. 5

3

Color Vision

Light enters the eye and is focused on the retina by the lens and the aqueous humor. The

retina contains rods and cones. Cones contain photopigments and are sensitive to color.

Photoreceptors, which are a specialized type of neuron located in the retina, send signals to

retinal ganglion cells converting light into electrical signals. As these are transferred from the

cones to the retinal ganglion cells, the trichromatic sensations of the cones are converted into the

opponent process system. These impulses travel through the optic nerve and to the brain where

perception of color occurs.7

The rods contain rhodopsin which responds to a single photon of light but are not

sensitive to the wavelengths of that light so rods cannot distinguish color. Cones respond to high

levels of light and are sensitive to a particular wavelength. Cones contain three different light

sensing pigments: ertholable (R cones) which are sensitive to the longer red wavelengths,

chorolabe (G cones) which are sensitive to the medium green wavelengths and cyanolab (B

cones) which are sensitive to the shorter blue wavelengths of light. These cones signals are not

distinct, but are overlapping allowing humans to see discriminate minute differences in color.

Where the cones lie and how their signals blend with each other determine how we see a color.17

Optical Blending

Optical effects occur in a variety of related forms, three of which are: 1) simultaneous

contrast, the effect adjacent color areas have on each other, 2) successive contrast, the afterimage

effect, and 3) optical blending which has a spatial component and causes a blending of colors.

This study focuses on the third. The phenomenon of optical blending occurs when two separate

colors are juxtaposed such that when viewed they are seen as yet another color or variation of the

4

original colors. Optical blending is described by various names: partitive mixing10, optical

mixing3,8,16,18,19, apparent intermixture11 and assimilation effects13.

Chevreul (1854) referred to optical blending as “mixture of colors” and defined it as

follows: “There is a mixture of colours whenever materials of various colours are so divided and

then combined that the eye cannot distinguish these materials from each other: in which case the

eye receives a single impression.”8 What is seen are actually two separate colors, but because

of their size and/or proximity, the eye blends the two colors and the viewer sees yet a third color.

Lambert, Staepelaere and Fry call this phenomenon optical color mixtures. They

describe optical mixtures as being “produced by eye/brain responses to the placement of

colorants rather than the physical mixtures of light or colorants.”16

In a woven fabric, optical blending often occurs when one color is used in the warp

direction and another color in the filling/weft direction. The two colors of the yarns interact with

each other to form another color or color variation. Optical blending also involves a spatial

component. Viewed at close distance the colors appear separate but when viewed from a greater

distance they appear as one color. The size of the juxtaposed colors and the distance from which

they are viewed can influence the color that is observed.

The occurrence of these optical color mixtures is affected by many conditions, variable

with any given media. In a previous study of appearance of woven textiles, Joshi (1982)

addressed the behavior of colored yarns in woven textiles. “The apparent behaviour of coloured

yarns when woven depends upon many factors: (1) the count of the yarn, (2) the size of the

pattern, (3) the type of weave (4) juxtaposition of coloured area (5) the viewing distance (6) the

eye fatigue (7) position of the fabric (8) the type of the material of which the cloth is made (9)

the twist applied to the yarn of which the fabric is made (10) the illumination in which the fabric

5

is viewed (11) the capacity of the eye of the observer (12) planning of coloured areas to improve

the weave effect.”14 Any of these factors can be a variable in a woven fabric. The scope of the

current study was limited to the juxtapositions of the yarns at a specified and constant viewing

distance.

Additional study by Sharavova and Guseva (1998) addressed optical and spatial blending

and concluded that “By using two differently colored fibres and varying the character of the

weave, it is possible to obtain a variety of hues. Changing the type of weave alters not only the

surface finish of the material but also its color characteristics.”22 For the scope of this study, the

character of the weave, i.e. the weave structure, was constant so that comparisons were made

only on the variability of color and no other fabric characteristics.

Optical blending occurs also in other media. The Pointillist painting movement, lead by

Georges Seurat, utilizes the juxtaposition of small dots of paint to create impression of color and

to increase or decrease luminance.6,9 See Figure 2.1. Television and computer screens also

employ optical blending by using small rectangles of colored lights to produce all the colors seen

on the screen.

Figure 2.1 Georges Seurat’s, A Sunday on the La Grande Jatte

6

Instrumental Color Measurement

Instrumental measurement that eliminates the variability of human vision is now

available. Instruments and software are available by which color measurements can be taken.

Spectrophotometers measure light as a function of wavelength. These instruments vary by the

wavelengths measured, techniques used for those measurements, the sources of variation

designed to be measured and how they acquire the spectrum. Most commonly, they measure

absorption or reflectance.

Reflectance spectrophotometers are used to obtain precise color measurements. In this

type of instrument, the electrical signaling is a spectral reflectance factor with wavelength

sampling and bandwidths of 10 nanometers across the visible spectrum from 400 – 700

nanometers; hence, the instrument is designated as a thirty-one point color spectrophotometer.

These measurements quantify color based on a system that simulates what an average observer

sees.

Reflectance is measured and multiplied (wavelength by wavelength) by stored data

representing the standard observer function and the illuminant function. From this calculation,

the instrument produces tristimulus values (the amounts of a set of primary colors). CIE L*a*b*

values are calculated from these data as follows: L* = 903.3(Y/Yn) for Y/Yn ≤ 0.008856,

a* = 500[(X/Xn)1/3 – (Y/Yn)1/3] and b* = 200[(Y/Yn)1/3 – (Z/Zn)1/3], where X, Y & Z are the

tristimulus values with X representing red, Y representing green and Z representing blue. CIE

La*b* values correspond to Hering’s opponent theory of color vision. The three parameters

within the CIE La b system are L*, a* and b*. The L* scale ranges from zero (absolute black) to

100 (absolute white). The a* scale ranges from negative infinity (green) to positive infinity

(red). Similarly, the b* scale ranges from negative infinity (blue) to positive infinity (yellow).5

7

Natural Colour System

Various systems have been created to describe and represent color. The Natural Colour

System (NCS) is a color order system that is based on how human beings perceive color rather

than on relationships between the primary colors and their mixtures. In common with the

opponent theory of Hering, the system has four chromatic colors red (R), blue (B), yellow (Y)

and green (G). The three dimensional color space, a representation of which is shown in Figure

2.2 is double cone shaped and is organized with the elementary colors (hues) on the edges of a

circular plane. The white to black scale (lightness and darkness) is perpendicular to and cuts

through the center of the color plane with the most black and most white being at the tips of the

cone. Intermediate hues are noted by percentages of each elementary hue that composes it

represented in Figure 2.3. An example is Y30R which represents a yellow with 30% red.

Figure 2.2 Figure 2.3 NCS Colour Space NCS Colour Wheel

This color space is based on a principle of similarity referred to as ‘nuance’. Unique to

this system is ability to establish the relationship between equivalent whiteness, blackness and

chromaticity without regard to hue chosen.5,23 An example of one color triangle is represented in

Figure 2.4. A whiteness scale and a blackness scale of 0-100 are established. The same degree

of blackness can be found on a parallel line between W (whiteness) and C (chromaticity). The

same degree of whiteness can be found on a parallel to line between S (blackness) and the C

8

(chromaticity). The same degree of chromaticity can be found on a line parallel to the W

(whiteness) and S (blackness). The nuance is established by using the intersection of the two

points on which the color of interest falls. See Figure 2.5. Any color can be defined by the three

numbers added together, W(whiteness) + S(blackness) + C(chromaticity) = 100. An example is

nuance 1050. The number 10 is the degree of blackness (S). The number 50 is the degree of

chromaticity. The remaining 40, though not represented in the number, is the degree of

whiteness (W). The same relative nuance can be found between any hue triangle and another.23

Figure 2.4 Figure 2.5

NCS Colour Triangle NCS Notation Description

9

CHAPTER THREE

METHODS AND PROCEDURES

For this study samples of blended color blocks of known composition were woven and

used to compare human visual assessments with instrumental color measurements. A standard

size of juxtaposed colors and constant viewing distance were used, thereby eliminating any

variability that a change in these two conditions might cause. The methodology used in the pilot

study was used in this study with only slight variation.

A number of limitations in the pilot study were eliminated in this research as the

researcher had control of the dyes, dyeing process and weaving process. Other limitations will

be discussed in subsequent sections of the Procedures chapter.

Preparation of Samples

Samples were prepared from Henry’s Attic “Pony” yarn purchased from the Yarn Barn of

Kansas. This two-ply wool yarn has a yarn linear density of 2835 yards per pound1 and twist of

5 per inch2. Wool was chosen in order to be consistent with the pilot study and since it was easy

to dye. Acid dyes used were from Jacquard Products. The names, company color numbers,

mixtures and respective Colour Index numbers are described in Appendix A. Yarns were dyed

to match, as closely as possible, colors in the NCS color order system.

A piece was woven that included all four colors in warp and the same four colors in the

weft(filling) It was woven in plain and balanced weave. This was consistent with the pilot

study. Plain and balanced weave provided the most yarn interlacements possible and at equal

increments so that optimum optical blending was achieved. The blocks were woven at

approximately 20 x 20 yarns per inch fabric count. The size of the individual woven color blocks

was four inches square. The fabric was cut into individual color blocks for ease of handling

10

during instrumental and visual testing. This produced six blended color blocks. See Figure 3.1

which is a photograph of the individual woven color blocks that were used.

Figure 3.1 Blended Color Blocks Used for Visual Assessments

The size of the samples in the current study may have been a limitation. Larger samples

may produce different results. Because the samples are handwoven, there is some inevitable

unevenness in the woven structure. This unevenness was definitely a limitation. Some areas of

the blended block were slightly more of one color than the other. To maintain consistency, all of

the blended blocks were shown to each of the participants with the same orientation. The upper

left hand corner was marked and always mounted that direction.

Instrumental Measurement of Color Blocks

The instruments and materials used in this phase of the study were the handwoven color

blocks, the Gretag Macbeth CE-7000A spectrophotometer with spherical geometry, and Gretag

Macbeth Optiview software, version 1.7. CIE L*a*b* measurements were taken using a one-

inch aperture. The 10° observer function (field of view) and the D65 illuminant were used.

Color block samples were presented to the port with the warp oriented in the same

direction for each measurement. A neutral gray fabric was placed behind the block to control for

any transmission through the specimen while measurement was taken. This neutral gray fabric

11

was applied to a stiff cardboard to prevent “pillowing” or deformation while the sample was in

the spectrophotometer port.

Card Selection Process

For the visual assessment portion of the study, participants were asked to compare the

blended color block and a set of NCS color cards. In preparation for this step, NCS color cards

were chosen by the researcher. In order to allow for differences in what participants might

observe, hue and nuances were chosen at increments of one NCS step away in each of the

directions within the NCS color space. The nine cards are described as follows. A “target” card,

i.e., that card whose instrumental measurement most closely matched the instrumental

measurement color block of interest, was selected. Two more cards were chosen, one that was

one step more whiteness and another that was one step more blackness than the target card.

Chroma was considered and cards were selected with one step more in chromaticity and one step

less in chromaticity than the target card with more whiteness and more blackness within each

step. For hue differences, cards were selected at one hue lower and one hue higher than the

target card but at the same nuance. A chart that includes the NCS color cards used and the

CIEL*a*b* measurements associated with those cards appears in Appendix B. Figure 3.2

contains a description of the card with the corresponding code number. Figure 3.3 shows all of

the color cards used in the visual assessments.

Table 3.1 Card Descriptions and Corresponding Code Numbers

Code # Card Description Code # Card Description 1 target 6 less chroma (more white) 2 more white 7 less chroma (more black) 3 more black 8 same nuance, lower hue 4 more chroma (more white) 9 same nuance, higher hue 5 more chroma (more black)

12

target more white

more black

more

chroma light

more chroma

dark

blendedfabric block

less chroma

light

less chroma

dark

same nuance

hue lower

same nuance

hue higher

Layout of Cards and Samples

Figure 3.2 Cards Used for Visual Assessments

The researcher was unable to dye the yarn to get an exact match to an NCS card to be

used as a target. Therefore, the cards which had measurements that most closely matched the

measurements on the blended blocks were used as target cards. A difference in these two sets of

measurements may also be the result of texture differences between the woven fabric sample and

the smooth surfaced cards.

The target card, R40B 5020, for the red blue blended block was somewhat darker and

slightly more red. For the green red blended block, the target card, Y30R 6010, was slightly

more red and less yellow. Card B70G 4040, the target card for the green blue was lighter and

13

more green. The target card, G30Y 3030, for the blue yellow blended block was somewhat

darker with somewhat more green and less yellow. For the yellow green blended block, the

target card, G40Y 2050, was slightly darker, somewhat less green and more yellow. The target

card, Y30R 3050, the yellow red blended block was slightly lighter, slightly more red and

slightly less yellow. A numerical comparison of the blocks, the target cards, and the

subsequently chosen cards appears in Appendix B.

Human Visual Assessments

Participants were twenty volunteers. They were University of Georgia female students in

their twenties. Since this study was conducted with only one age group and only females, testing

of other age groups and/or a group of males might produce different results. To prevent any

possible bias, students were solicited who had no color training in art or science and did not

already know the researcher, although recent work done by Revels20 suggests that level of

experience and training has no effect on the ability to assess color differences.

Prospective participants were first tested for color discrimination ability and screened for

areas of color confusion that would also have revealed any possibility of colorblindness. This

testing was done using the Farnsworth-Munsell 100 Hue Test in a MacBeth Spectra Light II box

at the daylight setting. Participants with a score of at least average discrimination ability and

with no visual anomalies were asked to participate in the study. Levels of discrimination are pre-

defined with the test.

Within three weeks, participants returned to evaluate the samples. All who volunteered

were eligible to participate. Different results may have been attained if color discrimination

testing and blended blocks card matching had been done in the same session.

14

The room was darkened with all the window blinds closed and all lights off except for the

light box illumination. Participants viewed the fabric blocks and cards in a MacBeth Spectra

Light II box at the daylight setting. Their selections were made from a seated position twenty-

six feet away from the light box. This distance was selected because preliminary evaluation with

two other volunteers demonstrated that for these fabrics, this was the minimum distance at which

optical blending occurred. Fabric blocks were presented with woven fabric block in the center

and one card above, one card to the left, and the third card to the right of the block as in the

Figure 3.3 below.

Figure 3.3 Sample of Card Arrangement Used for Visual Assessments

Preliminary evaluations showed that visual assessment of color differences was more

easily facilitated when there is no separator between the areas being compared; therefore the

researcher eliminated this separation by slightly overlapping the cards onto the fabric block. The

fabric blocks and the cards were the same size and, as previously stated, the fabric blocks were

presented in a consistent orientation.

In total, there were six blended color blocks to evaluate and nine cards from which to

choose for each blended color block. Subjects were shown each of the blended color blocks

separately and presented a set of the selected NCS color cards to view. Participants answered by

saying the letter for the position of the card that they chose. Participants were asked to turn

around and face away from the light box each time the researcher made a change of cards and

15

fabric blocks. These cards were presented in three sets of three cards each. Three cards were

randomly chosen and the participant was asked to choose the card that was “most closely the

same color as the fabric block in the center”. A second set of three more cards were chosen from

the remaining cards and the same instructions were given. The same procedures were followed

for a third set. The three cards selected from each of the three preceding groups were then

presented in the final set and the same instructions were repeated. The participant selected the

card that they felt was most closely the same color as the blended color block. Participants were

not told that the final set of cards included their previously selected cards. The eliminated and the

selected cards in each group were recorded. Each color block and its card sets were presented to

the participants twice and in random order. Other card placement combinations may produce

different results. An example of the sheet used to record participant’s choices is included in

Appendix D.

16

CHAPTER FOUR

RESULTS

The results are separated into two sections. The first section reviews the results of the

human visual assessments and card choices made by the participants. The second section

analyzes the point in the human visual assessments at which the target card was eliminated or

chosen.

Since the distance of viewing was determined to be twenty-six feet from the light box the

use of a two degree observer function (a smaller field of view) for the measurements may have

been more appropriate. The decision was made to continue use of the ten degree observer

function, since it had been used in the pilot study and in the original NCS card measurements. In

most cases, CIE L*a*b* measurements calculated for two degree and ten degree are not

appreciably different.

Table 4.2, a summary of Table 4.1, presents information on the number of times each

card was selected along with identification of the cards most frequently selected for each of the

blended color blocks.

Analysis of Cards Chosen

A tabulation of the cards chosen by each of the participants is presented in Table 4.1.

Overall the participants chose three cards more frequently than the others. There were nine

possible cards from which to choose. Table 4.3 details these results.

17

Table 4.1 Number of Times Participants Chose Cards

Card Number 1 % 2 3 4 5 6 % 7 8 9 %

Total % of 1, 6 & 9

Participant A 4 33 1 2 17 5 42 92 B 4 33 2 1 8 1 4 33 74 C 2 17 3 2 2 17 1 1 1 8 42 D 2 17 1 2 1 2 17 1 3 25 59 E 2 17 1 3 25 2 4 33 75 F 2 17 1 2 17 2 5 42 76 G 3 25 2 2 1 2 0 1 1 8 33 H 3 25 1 2 3 25 3 25 75 I 6 50 4 33 2 17 100 J 4 33 3 2 17 1 2 17 67 K 0 1 7 2 0 2 0 0 L 5 42 2 1 8 1 3 25 75 M 3 25 1 1 1 2 17 4 33 75 N 2 17 2 1 2 17 2 3 25 59 O 3 25 3 25 1 5 42 92 P 4 33 1 2 17 1 4 33 83 Q 3 25 1 2 2 17 4 33 75 R 4 33 1 2 17 1 4 33 83 S 4 33 2 17 6 50 100 T 6 50 1 1 2 17 2 17 84 66 11 10 19 12 39 5 13 65

18

Table 4.2 Summary of Number of Times Each Card Was Chosen

Card # Card Name

Red Blue

Green Red

Green Blue

Yellow Green

Blue Yellow

Yellow Red

Total ofEach

Card #

1 target 15

(38%) 6 5 25

(63%) 4 11

(28%) 66

(28%) 2 more white 2 3 1 0 1 4 11 3 more black 2 1 1 2 3 1 10

4 more chroma (light) 0

10 (25%) 1 1 0 7(18%) 19

5 more chroma (dark) 1 1 0 5 0 5 12

6 less chroma (light) 3 0

27 (68%) 3 2 4

39 (16%)

7 less chroma (dark) 1 1 2 0 1 0 5

8 nuance before 8 (20%) 1 1 0 2 1 13

9 nuance after 8 (20%) 17

(43%) 2 4 27

(68%) 7(18%) 65

(27%) out of 40 possible choices per card 240 total

Table 4.3

Overall Analysis of Card Choices

Card # Description # of Choices % #1 target 66 28% #6 less chroma, lighter 39 16% #9 same nuance, one hue higher 65 27%

Total (out of 240) 170 71%

The participants chose card #1, the target card, for twenty-eight percent of their choices.

This is the card whose instrumental measurements were the closest to the instrumental

measurements of the specified blended color block. Twenty-seven percent of the choices were

19

card #9, the card that was the same nuance as the target but one hue higher. This card has less of

the first color and more of the second color than the target card. Card #6, the lighter card of the

two with less chroma was chosen for sixteen percent of the choices. These cards account for

seventy-one percent of the total cards chosen overall.

The distribution of results was similar when the chosen cards were analyzed for three of

the blended color combinations. Table 4.4 details these results.

Table 4.4 Card Choices by Blended Color Block

Blended Color Block Card # Description %

blue yellow #9 same nuance, one hue higher 68%

green blue #6 less chroma, lighter 68%

yellow green #1 target 63%

green red #9 #4

same nuance, one hue higher more chroma, lighter

43% 25%

red blue #1 #8 #9

target same nuance, one hue lower same nuance, one hue higher

38% 20% 20%

yellow red #1 #4 #9

target more chroma, lighter

same nuance, one hue higher

28% 18% 18%

Three of the blended color blocks and the cards chosen as a match to them have fairly

consistent results. The green blue blended color block was matched by sixty-eight percent of the

20

participants to card #6, B70G 4030, which was the lighter of the two cards with less chroma (less

color). Sixty-three percent of the participants chose card #1, G40Y 2050, the target card as the

match for the yellow green blended color block. Card number #9, G40Y 3030 was chosen as the

match for the blue yellow blended color block sixty-eight percent of the time. This is the card

that is the same nuance as the target but one hue higher (less green and more yellow).

Trends in the results are less clear with the red blue, green red and the yellow red blended

color blocks. For the red/blue blended color block, thirty-eight percent of the participants chose

the target card, card #1, R40B 5020. Another forty percent were evenly split between R30B

5020, the same nuance as the target at one hue lower (less red and more blue) and card #9, R50B

5020, the same nuance one hue higher (less red and more blue). Addition of the choices for card

#1 and #9 totals fifty-eight percent.

Forty-three percent of the participants chose card #9, Y40R 5020 as the closest card for

the green red blended color block. This is the card which is the same nuance as the target but

one hue higher (less yellow and more red). Another twenty-five percent of the participants chose

card #4, Y30R 5020, the lighter of the two cards with more chroma.

The yellow red blended color block had the least clear results. Eleven percent of the

participants chose the target card, Y30R 3050, the card that most closely matches the blended

color block. Another seven percent of the participants chose card #6, Y30R 3040, the lighter

card of the two cards with less chroma. Card #9, Y40R 3050, was chosen by another seven

percent of the participants. This was the card with the same nuance as the target at a higher hue

(less yellow and more red).

Data analyzed by participant appear in Table 4.1. This analysis was consistent with the

findings of the analysis by blended color block. Two of the participants chose Cards #1, #6 and

21

#9 one-hundred percent of the time. Seventy percent of the participants chose those same cards

for, at least, seventy percent of their choices.

Participants did not generally choose cards that had simply more whiteness, simply more

blackness, the darker of the two cards with more chroma or the darker of the two cards with less

chroma. Instrumental color measurements on these cards are detailed in Appendix B.

Analysis of Target Card Elimination

An analysis of the point at which the target card was eliminated or chosen seemed to be

of value. Cards were presented to the participants in three groups of three cards. The choices

from each of those three groups were included in a final viewing group and participants chose

the final card from that group. Table 4.5 contains information as to whether or not the target

card was eliminated in one of the three preliminary viewings, eliminated at the final viewing or

not eliminated, i.e. chosen as the closest match. In each of two rounds of viewing, participants

could eliminate the target in one of the preliminary rounds, in the final viewing or choose the

target.

The cards were coded as follows. Card #1 was the target card, Card #2 was more white,

while Card #3 was more black. Cards #4 and #5 were cards with more chroma, the #4 being an

increment lighter than the target and #5 being an equal increment darker. Cards #6 and #7 were

cards with less chroma and the same increment differences as the more chroma cards. Card #8

was a card that was the same nuance as the target but one hue lower. Card #9 was a card that

was the same nuance as the target card but one hue higher.

22

Table 4.5 Elimination of Target Card

Red Blue

Green Red

Green Blue

Yellow Green

Blue Yellow

Yellow Red

Totals per person

Pers

on

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

Prel

imin

ary

Vie

win

gs

Fina

l Vie

win

g

Not

Elim

inat

ed

A 2 2 2 1 1 1 1 2 5 3 4B 1 1 2 2 1 1 1 1 2 5 3 4C 1 1 2 1 1 1 1 1 1 1 1 7 3 2D 2 1 1 1 1 2 1 1 1 1 6 4 2E 2 1 1 1 1 2 2 1 1 3 6 3F 2 1 1 1 1 2 1 1 1 1 4 6 2G 1 1 2 2 2 2 2 8 1 3H 1 1 1 1 2 1 1 1 1 2 6 3 3I 2 1 1 2 1 1 1 1 1 1 3 3 6J 1 1 2 1 1 2 2 1 1 4 4 4K 1 1 2 2 2 2 2 9 3 0L 1 1 1 1 1 1 2 2 2 3 4 5M 2 2 1 1 1 1 2 2 6 3 3N 2 2 1 1 1 1 1 1 1 1 5 6 1O 2 1 1 1 1 2 2 1 1 4 5 3P 1 1 1 1 1 1 1 1 2 1 1 4 5 3Q 1 1 2 1 1 2 2 1 1 7 2 3R 1 1 1 1 1 1 2 1 1 2 3 5 4S 1 1 2 1 1 2 2 1 1 2 5 5T 2 1 1 1 1 2 1 1 1 1 3 3 6

Total by

color 8 17 15 25 9 6 22 13 5 9 6 25 16 20 4 17 12 11 97 77 66% of 40 20 43 38 63 23 15 55 33 13 23 15 63 40 50 10 43 30 28 40 32 28

23

Overall, for twenty-eight percent of the choices the target card was the selected card.

Broken down by blended color block combination, the results were as follows. For the red blue

blended color block, twenty percent eliminated the target card in one of the preliminary

viewings, forty-three percent eliminated it at the final viewing and thirty-eight percent selected it

as the “most close”.

A larger percentage, sixty-three percent, eliminated the target card at one of the

preliminary viewings for the green red color block, while another twenty-three percent

eliminated it at the final viewing. Only fifteen percent of the time was it chosen as the card that

was the most close.

For the green blue blended color block, fifty-five percent of the time the target card was

eliminated as the card that was the most close in one of the preliminary viewings. Thirty-three

percent eliminated it in the final viewing, while it was only selected thirteen percent of the

choices.

The yellow green blended color block showed different results. Sixty-three percent chose

the target card as the card that most closely matched the blended color block. Only twenty-three

percent eliminated the target card at one of the preliminary viewings and only fifteen percent

elimination occurred at the final viewing.

For the blue yellow blended color block, forty percent eliminated the target card in one of

the preliminary viewings and for another fifty percent, it was eliminated at the final viewing. For

only ten percent was it selected as the card that most closely matched.

For forty-three percent of the selections, the target card was eliminated in one of the

preliminary viewings as the match for the yellow red blended color block. For another thirty

24

percent, it was eliminated at the final viewing, while it was selected as the card that most closely

matched by twenty-eight percent.

25

CHAPTER FIVE

SUMMARY AND RECOMMENDATIONS

The researcher does not believe that any specific conclusions can be drawn from this

research. Subsequent study would be required. The following paragraphs present information

that can be obtained from this research and recommendations for further study.

Analysis of Cards Chosen

It is noted that none of the three color space directions is totally independent. As one

direction changes, the other two are effected.

In reviewing the results of this study, there is strong evidence to support the following

statement. When asked to choose a card that most closely matches the blended color block, the

participants perceived either the target card, Card#1, the card whose measurements most closely

matched the measurements of the blended color block, or Card #9, the card which was the same

nuance but one hue higher than the target. Some participants also perceived a lighter version of

less chroma, Card #6, as the card that most closely matched.

The choice of target card occurred for twenty-eight percent of the choices indicating the

subjects indeed saw the target as the closest match. By their choice of hue higher card, #9,

participants demonstrated that they perceived that there was a different mix of the two colors

used to form the blended color block than the mix indicated by the target card which was

instrumentally the closest match. Sixteen percent perceived a lighter and less chroma color as

the closest match. These three card choices represented seventy-one percent of the subjects. See

Tables 4.1 and 4.2 for tabulation and summation of choices made by participants.

26

An evaluation was also made by each of the blended color blocks separately. In sixty-

eight percent of the selections, participants chose card #6 as the one that most closely matched

the green blue blended color block. They saw less chroma and more lightness than the target.

For the yellow green blended color block, the participants chose the target card, card #1,

sixty-three percent of the time, even though the target card was more yellow and slightly less

green than the blended color block. Since the target card is somewhat darker, this may account

for these differences.

Card # 9 was chosen to most closely match the blue yellow blended color block in sixty-

eight percent of the selections. The test group perceived the blended color block as having a

different mix of yellow and green than the target card.

When red was used with each of the other colors to form the blended color blocks, the

participants, as a group, made a wider range of choices. Even when the range of choices was

wider, the Card #1 and Card #9 were still chosen more often than the other cards. In the other

three blended colors blocks (the ones without red), Card #1 and Card #9 account for 58 choices

out of 240 possible choices.

For the red blue blended color block, fifty-eight percent of the participants perceived

Card #1 or #9 as the closest matches. They either perceived the target as the best match or they

perceived a card with more blue and less red as a better match.

The subjects had a similar perception for the green red blended color block. Card #9 was

chosen for forty-three percent of the selections. The participants perceived a different mix card

of yellow and red than the target card indicated.

27

Participants, as a group, made the widest range of choices when viewing the yellow red

blended color block. Again, they chose the target card, Card #1 the most frequently, but at only

twenty-eight percent of the choices. As in other colors, they also chose Card #9.

Based on the results, it can be concluded that for the group of subjects who participated

in this study, the card that was most closely the same color as the blended color block was one of

three cards. By twenty-eight percent, they selected the target card, the card whose instrumental

measurements most closely matched the blended color card. Another twenty-seven percent

perceived the blended color block as the same nuance but one hue higher, i.e. they perceived a

different mix of the two colors used to form the blended block. Thirdly, sixteen percent

perceived the blended color block as less chroma and lighter.

Only occasionally did participants see the blended color blocks as simply darker, simply

lighter, with more chroma and darker or with less chroma and darker.

Analysis of Target Card Elimination

Among the blended color blocks, a particular pattern did not emerge. Overall,

approximately one third of the time the target card was eliminated in one of the three preliminary

viewings, while another third of the time it was eliminated in the final viewing. In the last one

third, the target card was the chosen card. When evaluated by individual participant, only five of

the twenty participants varied from this pattern.

Recommendations

Further study could be conducted in this area by simply repeating this experiment with

more precisely dyed colors. Other color combinations and the visual perception of those

combinations could be studied and compared to this research. Other conditions of the study

could be varied such as size of swatch, density of plain weave structure and, therefore viewing

28

distance could be altered to compare results obtained. The 2°observer function could be used in

further study. Visual testing could be performed with males, other age groups or other ethnicities

as they might make different selections.

29

REFERENCES

1. ASTM D 1577-01: Standard Test Method for Linear Density of Textile Fibers 2. ASTM D 1423-02: Standard Test Method for Twist in Yarns by Direct-Counting 3. Albers, Josef, Interaction of Color, Yale University Press, New Haven, 1963, entire text 4. Backhaus, Werner G.K., Kliegl, Reinhold, Werner, John S., Editors, Color Vision, Perspectives from Different Disciplines, Walter de Gruyter, New York, 1998, pages 17-18 5. Berns, Roy S., Billmeyer and Saltzman’s Principles of Color Technology, Third Edition, John Wiley & Sons, Inc., 2000 6. Berns, Roy J., Rejuvenating the Color Palette of Georges Seurat’s A Sunday on the La Grande Jatte, Color Research and Application, Volume 31, Issue 4, August 2006, pages 278-293 7. Carlson, Neil R., Physiology of Behavior, 4th Edition, Allyn and Bacon, Boston, Massachusetts , 1991, pages 178-185 8. Chevreul, M.E. and F. Birren, The principles of harmony and contrast of colors and their applications to the arts, 1967, Reinhold Publications, New York, p. 256. 9. Dunstan, Bernard, Painting Methods of the Impressionists, Watson-Guptill Publications, New York, 1976, p. 129 10. Gerritsen, Frans, Theory and practice of color: a color theory based on laws of perception, Van Nostrand Reinhold, New York, 1975. 11. Eastlake, Charles Lock, translator, Theory of Colours, Johann Wolfgang von Goethe, The MIT Press, Cambridge, Massachusetts and London, England, pages 226-229 12. Grossicki, Z., Watson’s Textile Design and Colour, Revised 1975, original Version 1912, Butterwoth and Co., 1975, pages 138-144 13. Jameson, Dorothea, From Contrast to Assimilation: In Art and in the Eye, Leonardo, Volume 8, Issue 2, Spring 1975, pages 125-131 14. Joshi, R.P., Apparent Change of Colour in Woven Textiles, The Indian Textile Journal, Volume 92, May 1982, p. 71 15. Knutson, Linda, Synthetic Dyes for Natural Fibers, Revised Edition, 1986, Interweave Press, Inc., Loveland, Colorado, p. 12-44 & 101-118

30

16. Lambert, P., B. Staepelaere, and M.G. Fry, Color and Fiber, 1986, West Chester, Pa.: Schiffer Publications, p.57-60 17. Long, Jim and Joy Turner Luke, The Munsell® Student Color Set, Second Edition, Fairchild Publications, New York, 2001, p. 40-49 18. Nassau, Kurt, The Physics and Chemistry of Color, Wiley & Sons, New York, 2001, pages 13-14 19. Osborne, Roy, Lights and Pigments, Colour Principles for Artists, Harper & Row Publishers, New York, 1980, pages 114-120 20. Revels, Carol Tomasino, Describing Color Differences: How Good are Your Color Comments?, AATCC Review, Volume 7, Issue 1, January 2007, pages 40-44 21. Rivlin, Joseph, The Dyeing of Textile Fibers: Theory and Practice, 1992, Philadelphia College of Textiles and Science, p. 84-98 22. Sharavova, N.I. and N.Y. Guseva, Determination of Color Characteristics in Optical Mixing of Colors in Polymer Fibres, Fibre Chemistry, 1998. 30(6): p. 387 23. www.ncscolor.com, Natural Colour System company website, retrieved 10/7/2006

31

http://www.ncscolor.com/

APPENDIX A

DYES FROM JACQUARD PRODUCTS

Blue Green Red Yellow

Company Color Name Sky Blue Emerald Crimson Sun Yellow

Company Color Number 621 629 619 601

Mixture **** Turquoise 624 Red 617 ****

Yellow 601 Blue 621

Colour Index numbers Blue 129 Blue 7 Red 266 Yellow 49

Yellow 49 Blue 324

32

APPENDIX B

CIEL*a*b Measurements of Cards Used for Assessments

Yellow Green Blue Yellow CIEL*a*b* CIEL*a*b*

Code # Card Name Hue Nuance L a b Hue Nuance L a b

Blended Color Block 64.89 -20.42 41.05 60.56 -13.55 22.2

1 target G40Y 2050 66.48 -17.86 37.79 G30Y 3030 63.14 -15.47 19.13

2 more white G40Y 1050 75.55 -19.57 39.54 G30Y 2030 71.22 -15.43 19.89

3 more black G40Y 3050 57.32 -16.46 33.62 G30Y 4030 54.72 -13.81 17.21

4

more chroma (more white)

G40Y 1060 73.48 -22.14 47.25 G30Y 2040 68.52 -20.63 26.26

5

more chroma (more black)

G40Y 2060 62.74 -19.28 42.08 G30Y 3040 60.09 -19.04 24.33

6

less chroma (more white)

G40Y 2040 69.29 -15.18 31.46 G30Y 3020 66.49 -10.63 13.46

7

less chroma (more black)

G40Y 3040 61.13 -13.74 27.86 G30Y 4020 58.01 -9.85 12.65

8

same nuance lower hue

G30Y 2050 64.84 -20.93 31.3 G20Y 3030 61.99 -17.47 15.43

9

same nuance higher

hue

G50Y 2050 68.38 -13.44 40.61 G40Y 3030 63.62 -10.35 21.97

33

APPENDIX B CIEL*a*b Measurements of Cards Used for Assessments

Continued

Yellow Red Red Blue CIEL*a*b* CIEL*a*b*

Code #

Card Name Hue Nuance L a b Hue Nuance L a b

Blended Color Block 58374 18.06 39.81 44.75 10.34 -6.37

1 target Y30R 3050 57.23 20.05 38.3 R40B 5020 46.97 11.81 -7.22

2 more white Y30R 2050 66.14 21.03 42.59 R40B 4020 54.99 11.07 -7.34

3 more black Y30R 4050 49.59 18.87 35.19 R40B 6020 36.99 12.52 -7.56

4


Y30R 2060 63.29 23.86 46.79 R40B 4030 49.29 16.89 -10.41

5


Y30R 3060 54.71 23.54 43.24 R40B 5030 39.42 17.18 -10.31

6


Y30R 3040 60.58 16.39 33.36 R30B 4020 54.95 12.69 -3.7

7


Y30R 4040 52.78 15.82 30.82 R30B 6020 37.23 14.15 -4.04

8 same

nuance lower hue

Y20R 3050 59.46 15.28 42.69 R30B 5020 47.52 13.6 -4.04

9 same

nuance higher hue

Y40R 3050 56.57 23.21 36.00 R50B 5020 47.16 8.97 -10.93

34

APPENDIX B CIEL*a*b Measurements of Cards Used for Assessments

Continued

Green Red Green Blue CIEL*a*b* CIEL*a*b*

Code # Card Name Hue Nuance L a b Hue Nuance L a b

Blended Color Block 48.62 4.52 14.49 -23.67 -0.93

1 target Y30R 6010 47.85 5.56 11.91 B70 G 4040 48.12 -27.06 -0.96

2 more white Y30R 5010 53.96 5.39 13.05 B70 G 3040 58.66 -27.65 -1.14

3 more black Y30R 7010 39.11 4.82 9.96 B70 G 5040 38.24 -25.93 -1.39

4


Y30R 5020 50.1 9.11 19.15 B70 G 3050 52.72 -34.86 -0.80

5


Y30R 6020 43.01 8.89 16.77 B70 G 4050 43.13 -34.41 -0.75

6


Y20R 6005 48.94 2.14 7.6 B70 G 4030 54.5 -21.41 -1.23

7


Y20R 7005 40.13 1.63 5.4 B70 G 5030 44.39 -20.72 -1.35

8

same nuance lower hue

Y20R 5020 51.72 7.24 20.69 B60 G 4040 48.66 -27.11 -3.76

9

same nuance higher

hue

Y40R 5020 50.65 10.67 17.58 B80 G 4040 48.77 -28.22 1.88

35

APPENDIX C

Comparison of Blended Color Blocks, Target and Chosen Cards Yellow Green

L* a* b* Blended Color Block Measurement 64.89 -20.42 41.05

Target card, #1, G40Y 2050 66.48 -17.86 37.79 Chosen Card #1, (63%) 66.48 -17.86 37.79

Blue Yellow L* a* b*

Blended Color Block Measurement 60.56 -13.55 22.20 Target card #1, G30Y 3030 63.14 -15.47 19.13

Chosen Card #9, G40Y 3030 (68%) 63.62 -10.35 21.97 Yellow Red

L* a* b* Blended Color Block Measurement 58.74 18.06 39.81

Target card, #1, Y30R 3050 57.23 20.05 38.30 Chosen Card #1 (28%) 57.23 20.05 38.30

Chosen Card #4, Y30R 2060 (18%) 63.29 23.86 46.79 Chosen Card #9, Y40R 3050 (18%) 56.57 23.21 36.00

Red Blue L* a* b*

Blended Color Block Measurement 44.75 10.34 -6.37 Target card, #1, R40B 5020 46.97 11.81 -7.22

Chosen Card #1, (38%) 46.97 11.81 -7.227 Chosen Card #8, R30B 5020, (20%) 47.52 13.60 -4.04 Chosen Card #9, R50B 5020, (20%) 47.16 8.97 -10.93

Green Red L* a* b*

Blended Color Block Measurement 48.62 4.52 14.49 Target card, #1, Y30R 6010 47.85 5.56 11.91

Chosen Card #4, Y30R 5020, 25% 50.10 9.11 19.15 Chosen Card #9, Y40R 5020, (43%) 50.65 10.67 17.58

Green Blue L* a* b*

Blended Color Block Measurement 52.97 -23.67 -0.93 Target card, #1, B70G 4040 48.12 -27.06 -0.96

Chosen Card #6 (68%), B70G 4030 54.50 -21.41 -1.23

36

APPENDIX D

SAMPLE OF RECORDING SHEET Yellow Red

Participant

CODEtarget Y30R 3050 1 more white Y30R 2050 2 more black Y30R 4050 3 more chroma (light) Y30R 2060 4 more chroma (dark) Y30R 3060 5 less chroma (light) Y30R 3040 6 less chroma (dark) Y30R 4040 7 same nuance, lower hue Y20R 3050 8 same nuance, higher hue Y40R 3050 9

Participant Selections

Round 1 Round

2 eliminated eliminated Set 1 choice eliminated eliminated Set 2 choice eliminated eliminated Set 3 choice eliminated eliminated Final choice

37

optical blending: a comparison of spectrophotometric

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