Imagesetter output resolution in newspaper color image reproduction

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5-1-1998

Imagesetter output resolution in newspaper color

image reproduction

Sabine Süsstrunk

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Recommended Citation

Imagesetter Output Resolution in Newspaper

Color Image Reproduction

by

Sabine

Siisstrunk

A thesis

submitted

in

partial

fulfillment of

the

requirements

for

the

degree of

Master

of

Science in

the

School

of

Printing

Management

and

Sciences

in

the

College

of

Imaging

Arts

and

Sciences of

the

Rochester Institute

of

Technology

March 1993

School of Printing Management and Sciences

Rochester Institute of Technology

Rochester, New York

Certificate of

Approval

Master's Thesis

This is to certify that the Master's Thesis of

Sabine Siisstrunk

With a major in Electronic Publishing

has been approved by the Thesis Committee as satisfactory

for the thesis requirement for the Master of Science degree

at the convocation of

Thesis Committee:

Frank Cost

Thesis Advisor

Marie Freckleton

Graduate

Program

Coordinator

Permission

to

Reproduce

Title

of

the

Thesis:

Imagesetter Output Resolution in Newspaper Color Image

Reproduction.

I,

Sabine

Siisstrunk,

hereby

grant permission

to the

Wallace

Memorial

Library

of

RIT

to

reproduce

my

thesis

in

whole or

in

part.

Any

reproduction will not

be for

commercial use or profit.

Acknowledgments

The

author would

like

to

acknowledge

the

following

individuals for

their

assistance.

Each

contributionwas

invaluable

for

the

productionand completion of

this thesis.

Mr. J. A.

Stephen

Viggiano

of

RIT

Research

Corporation for

providing

usable

file

formats

and

for

helping

with

the

evaluation of

the

resolutiontargets.

Mr.

Jim Hamilton

of

Linotype-Hell

Company

for

the

output of

the

separations.

Professor

Frank

Cost

of

the

School

of

Printing

Management

and

Sciences

at

RIT

for

providing

the

resolution

target

file.

Also,

his

encouragement

along

the

way

was

very

much appreciated.

Mr. Alex

Letko for

stripping

and

printing

the test

matrix.

Mr.

Mike

Stokes

of

Apple

Computers for

helping

to

set

up

the

paired

comparison experiment and

for explaining

the

intricacies

of statistical analysis.

Professor Kenneth Hoffmann

of

the

Printing

Department

of

The National

Institute

of

the

Deaf

at

RIT

for

proof reading.

On

a more personal

note,

many

thanks

to

Dr.

Marianne Schonenberger

Tomamichel

and

Professor

Franz Tomamichel. Without their

encouragement and

help,

the

authorwould never

have been

in

a position

to

write

this

thesis.

Table

of

Contents

List

of

Tables

vii

List

of

Figures

x

Abstract

xii

Chapter

1.

Introduction

1

1.1

The

Problem

1

1.2

Its Background

and

Present

Significance

2

1.3

The

Reason

for Interest in

the

Study

3

Endnotes for Chapter

1

5

2.

Theoretical Background

6

2.1

Electronic Halftone

Reproduction

6

2.1.1

Input

6

2.1.2

The

Histogram

8

2.1.3

Output

12

2.2

Statistically

Valid

Methods

for

Visual Evaluation

of

Quality

....

16

Endnotes

for

Chapter 2

20

3.

Hypotheses

22

4.

Methodology

23

4.1

The

Choice

of

Imagesetter Resolutions

for

the

Study

23

4.2

The

Choice

of

Images for

the

Study

24

4.3

The

Design

of

the

Test

Matrix

26

4.4

The

Preparation

of

the

Images for Output

27

4.5

The

Output

of

the

Separations

30

4.6

Proofing,

Page

Assembly,

and

Plate

Making

32

4.7

Printing

33

4.8

Evaluation

of

Resolution Targets

and

Dot Shapes

34

4.9

Visual Evaluation

35

Endnotes

for Chapter

4

39

5.

Results

41

5.1

Physical Evaluation

of

the

Test

Matrix

41

5.1.1

Fresnel Zone Plates

41

5.1.2

Dot

Shapes

43

5.2

Visual

Evaluation

of

the Test Matrix

45

5.2.1

Analysis

of

the

Observers'

Results

45

5.2.2

Evaluation

of

the

Observer

Survey

51

5.2.3

Results of

the

Statistical Analysis

55

5.2.3.1

Woman

55

5.2.3.2

Street Cafe

56

5.2.3.3

Fruit Basket

56

5.2.3.4

Bicycle

56

5.2.3.5

All

Images

Combined

57

Endnotes

for

Chapter 5

58

6.

Summary

and

Conclusion

59

Appendices

Appendix

A

-Test Matrix

Design

64

Appendix

B

-Linotype-Hell

Recommendations for Screen Frequencies

and

Screen Angles

66

Appendix C

-Printed

Test Matrix

68

Appendix

D

-

Observer

Matrix

69

Appendix

E

-

Observer Results

Matrix

71

Appendix

F

-

Observer

Survey

73

Appendix G

-

Dot

Shapes

on

Proofs

and

Press Sheet

75

Appendix

H

-

Observer Results

77

Appendix

I

-Frequency

Matrices

82

Appendix

J

-

Proportion Matrices

88

Appendix

K

-z-Score

Matrices

and z-Score

Scales

94

Appendix L

- _z-Scales

105

List

of

Tables

Table

Page

1

-

Number

of

grey levels

for

each separation

depending

on

the

output resolution

14

2

-Image

characteristicsof

the

four images

used

in

the

study

25

3

-

Aim

dot

percentages and

corresponding

brightness

values

for

negativeseparations

29

4

-

Equipment

used

to

output

the

separations

for

the test

matrix

31

5

-

Plate

exposure

32

6

-

Equipment

used

for printing

the

test

matrix

33

7

-Frequency

response matrix of

the

image Woman

(total

of

32

observers)

46

8

-Frequency

response matrix of allresponses

(all

image

types

combined)

for

the total

group

ofobservers

46

9

-

Proportion

_{matrixof all}

four images

combined

(total group

of

observers)

47

10

-z-Score matrix of all

four

images

combined

(total group

of

observers)

49

11

-

Linotype-Hell

recommendations

for

screen

frequencies

and screenangles

(HQS)

for

Linotronic 530/500

with

PostScript

RIP

30

and

PostScript

software

52.3 N3

67

12

-

Observer

_matrix

70

13

-

Observer

results

Woman

78

14

-

Observer

results

Street Cafe

79

15

-

Observer

results

Fruit

basket

80

16

-

Observer

results

Bicycle

81

17

-Frequency

matrix

Woman

83

18

-Frequency

matrix

Street Cafe

84

19

-Frequency

matrix

Fruit

basket

85

20

-Frequency

matrix

Bicycle

86

21

-Frequency

matrix of all

four

images

87

22

-Proportion

matrix

Woman

89

23

-

Proportion

matrix

Street

Cafe

90

24

-

Proportion

matrix

Fruit

basket

91

25

-

Proportion

matrix

Bicycle

92

26

-

Proportion

matrixof all

four images

93

27

- _{z-Scorematrix}

Woman

95

28

-z-Score scale

Woman

96

29

- _{z-Score matrix}

Street Cafe

97

30

- _{z-Score scale}

Street

Cafe

98

31

- _{z-Score matrix}

Fruit

basket

99

32

- _{z-Score scale}

Fruit

basket

100

33

-z-Scorematrix

Bicycle

101

34

-z-Score scale

Bicycle

102

35

- _{z-Score matrix of all}

four

images

103

36

- _{z-Score scale ofall}

four

images

104

37

-z-Scale with

95

percent confidence

indicators Woman

106

38

- _{z-Scale with}

95

percentconfidence

indicators

Street Cafe

110

39

- _z-Scale

with

95

percent confidence

indicators Fruit

basket

114

40

-z-Scalewith

95

percent confidence

indicators Bicycle

118

41

- _{z-Scale with}

95

_{percent confidence}

indicators

of all

four

images

122

List

of

Figures

Figure

Page

1

-

Visual

effectofcorrectand

incorrect sampling

ratios

8

2

-

Brightness

changeof

the

image Woman

when

subtracting

30

from

each pixel value

9

3

-

Histogram

of

the

image Fruit

basket

10

4

-

A

2x2

spot matrix per

halftone dot

results

in

a

total

of

5

grey

levels

14

5

-

Approximation

of a

50

percentround

dot

in

a

4x4

spotgrid

vs. a

50

percent round

dot in

a

16x16

spot grid

15

6

-

User

interface

_of

"level"

command

in

Photoshop

2.0

(Image

Bicycle,

magenta

channel)

28

7

-

Fresnel

_{zone plates}

35

8

-

Smallest Fresnel

_{zone plates of}

the

test target

ateach resolution

on

the

proofs

(magnification factor:

34)

42

9

-

Smallest

Fresnel

_zoneplates

test target

at

846

spiand

1690

spi

outputresolutionon

the

press sheet

(magnification factor:

34)

44

10

-

Properties

_of

the

_normal

distribution

48

11

- _{z-Scales of}

the

different

observergroups

for

all

four images

combined

49

12

-z-Scale

including

intervals

of+/-

2

_z

for

_all

four images

combined

(total

group

ofobservers)

51

14

-

Dot

shapesateach outputresolution on

the

proofs and

the

press sheet

76

15

-z-Score scale

Woman

96

16

-z-Score scale

Street Cafe

98

17

-z-Scorescale

Fruit

basket

100

18

-z-Scorescale

Bicycle

102

19

-z-Scorescale of all

four images

104

20

-z-Scalewith

95

percent confidence

indicators

Woman

(professionals)

107

21

- _z-Scale

with

95

percentconfidence

indicators Woman

(others)

108

22

- _{z-Scale with}

95

_{percent confidence}

indicators Woman

(total)

109

23

- _{z-Scale with}

95

_{percentconfidence}

indicators

Street

Cafe

(professionals)

Ill

24

-z-Scale with

95

percentconfidence

indicators

Street

Cafe

(others)

112

25

-z-Scale with

95

percentconfidence

indicators Street Cafe

(total)

113

26

-z-Scale with

95

percentconfidence

indicators Fruit

basket

(professionals)

115

27

-z-Scale with

95

percentconfidence

indicators Fruit

basket

(others)

....

116

28

- _{z-Scale with}

95

percentconfidence

indicators Fruit

basket

(total)

117

29

-z-Scale with

95

percent confidence

indicators Bicycle

(professionals)

119

30

-z-Scale with

95

percent confidence

indicators

Bicycle

(others)

120

31

-z-Scale with

95

percent confidence

indicators Bicycle

(total)

121

32

- _{z-Scale with}

95

percent confidence

indicators

for

all

four images

(professionals)

123

33

-z-Scale with

95

percent confidence

indicators

for

all

four

images

(others)

124

34

- _{z-Scale with}

95

percent confidence

indicators for

all

four images

(total)

125

Abstract

The

use of color

in

newspaper

printing

has significantly

increased

over

the

last

few

years.

To

compete with other news

media,

advertising

as wellaseditorial

design had

to

become

more

visually

attractive,

using

more color graphics and

images.

The

concurrent

development

of

integrated

desktop

pre-press systems

facilitated

the

integration

of

color,

having

less

cost associatedwithnew

technology

purchases

than the traditional

high

end systems.

The

purposeof

the thesis

is

to

compare

different

outputresolutions of an

imagesetter

and

to

find

the

minimal output resolution

necessary

for

acceptable

quality

in

newspapercolor

image

reproduction.

The

speed of an

imagesetter,

which

is dependant

on

the

chosen output

resolution,

is

an

important factor

in

newspaper

turn-around time.

In

this study,

a matrix was

designed containing

various

test targets

and

four

different

images

with

different

image

characteristics at

four different

output

resolutions.

Most

imagesetters

on

the

market

today

support outputresolutions

that

approximate

the

four

selected

for

the

study

(846,

1016, 1270,

and

1693

spots

per

inch).

The

screen

frequency

of

the

images

was

85

lines

per

inch,

a common

screen

ruling

in

newspaper reproduction.

The

separationswere output on a

Linotronic

530

imagesetter.

The

output

time

varied

from

18

minutesatthe

lowest

resolution of

846

SPI

to

about

half

an

hour

at

the

highest

resolution of

1693

spi.

The

test

matrix wasprintedon

Consolidated

Newsprint

on anoffsetnewspaper

Goss

Community

press.

The

print application's spatial

resolving

power was evaluated

by

exarnining

Fresnel

zone plate resolution

targets

under magnification.

Due

to

ink

spreading,

no visible

difference

could

be detected

on

the

printed

test

matrix

between

the

different

output resolutions.

The

test

matrix was alsosubmitted

to

an audience

for

visual evaluation.

The

psychometric method applied was

the

paired comparison

method,

which

is

based

on

the

principle

that the

percentageof observers

preferring

astimulus

over

the

othergives a

direct

indication

of

how

the

two

stimuli

differ. In

this

study,

the

stimuli were

the

images

with

different

output resolutions.

Each

reproduction was paired with another

image

from

the

same

type,

but

with

another output resolution.

The

observers

had

to

indicate if

they

preferred

the

left

or right

image

of a pair.

The

criterion

for

evaluation was"better."

The

statisticalanalysis of

the

paired comparisonmethod

indicates

that

for

all

four images

combined, there

is

a

95

percent confidence

level

that

novisual

difference in

quality

between

the

four

resolutionscould

be detected

by

the

observers.

Experimental

noise,

specifically

registration,

skewed some of

the

individual

image

results.

As

a

result, the

first

hypothesis-the

visual

quality

of

images

reproduced

in

newspapers

is

not

dependent

on

the

imagesetter

outputresolutionabovea certain

limit for

a given set of print parameters-wasproven

to

be

correct.

However,

the

second

hypothesis-for

offset newspaper

printing

onconsolidated

newsprint at a screen

frequency

of

85

lpi,

the

resolution

limit lies between

1,000

and

1,200

SPi-has

to

be

rejected.

This

study

concludes

that

for

the

given print

parameters, the

resolution

limit is 846

spi.

Further

studies might even

indicate

a

lower limit.

To

summarize,

one of

the

major

disadvantages

of electronic

halftone

reproductions

today, namely

output

speed,

can

be

optimized

independently

from

technical

considerationssuch as

hardware

and software systems.

A

ininimal

output resolution can

be found

for

a given print application

by

exarnining

its

characteristics,

suchas

resolving

power and print contrast.

Any

image

outputat

a resolution

higher

than the

mirtirnum

does

not

improve

the

quality

of

the

reproduction,

and

only

slows

down

the

production

turn-around time.

Chapter

I

Introduction

1.1

The Problem

The

purpose of

the

study

is

to

compare

different

output resolutions of an

imagesetter

and

to

find

the

minimal output resolution

necessary

for

acceptable

quality

in

newspaper color

image

reproduction.

Considering

the

amount of

data

a color

image

file

contains,

the

speed with which an

imagesetter

can "write" a

file

is

an

important factor

that

influences

the turn-around

time

in

newspaper

production.

The higher

the resolution, the

longer

the

actual

imaging

ofan output

takes.

As

an

example, the

imaging

of a

file

at

1600

spotsper

inch

(spi)

takes

approximately

twice

as

long

than

at

800

SPI.

The four

chosen output resolutions

(846

spi, 1016 spi, 1270 spi,

and

1693

spi)

aresupported

by

most

imagesetters

on

the

market

today.

To

control

the

variables,

all

images

were written with

the

same

imagesetter

(Linotronic

530)

as

negative

film

separations with

identical

screen

frequency

and screen angles.

The

test

matrixwas printed on

Consolidated Newsprint

on an offset newspaper

Goss

Community

press.

The

printed matrix was submitted

to

a

test

audience

for

visual

evaluation,

judged

visually.

A

statistically

_{valid method}

had

to

be developed before

the

final

questioning

of

the

test

audience.

A

test

target,

a number of concentric circles

in

different

sizes,

was

included

to

measure

physically

the

limitations

of

the

different

output resolutions.

1.2

Its Background

and

Present Significance

The

use of color

in

newspaper

printing

has

significantly

increased

over

the

last

few

years.

To

competewith othernews

media,

newspaper

design

has become

more

visually

attractive,

integrating

morecolor

images,

text

and graphics.

Before

1984,

color

in

newspaper

printing

was

usually limited

to

special

inserts,

such as

separateadvertisementor

the

weekend magazine.

In

1984,

the

newly

founded

USA

Today

introduced

a new newspaper

design

concept,

using

color

aggressively

throughout the

paper

to

highlight

certaineditorial

departments

and

to

distinguish itself

from

other newspapers on

the

racks.

In

the

following

years,

most newspaper publishers

followed

suit.

By

1990,

86

percent of allnewspapers

printed editorial colorat

least

four times

aweek.1

At

the

same

time,

the

development

of electronic

publishing

technology

facilitated

the

integration

of color.

Page

layout

and

design

software

developments

enabled

the

assembly

of newspaperpageson

screen,

allowing

for

visual

(soft)

proofing before

the

page

is

physically

assembled.

Imagesetters,

the

newestgenerationof output

devices,

enabled

the

concurrentoutputof

text,

graphics and

images,

making stripping

a minimal

step

in

page production.

As

with

the development

of most

technologies,

speed

has been

amajor

and output

time

a newspaperpage required made

the

use of

imagesetters

unrealistic

for

daily

production,

even

considering

all

the

advantages of an

electronic

publishing

system.

But

as

the

processing

capabilities of raster

image

processors

(RIP)

and

the

speed of

PostScript

imagesetters

increase, they

become

a realalternative

to

newspaperpublishers.

Image

files

which

have

taken

hours

to

separate

just

a

few

years ago can

be

processed

today

in just

a

few

minutes.2

Limiting

the

outputresolutioncanspeed

up

the

output even

further.

1.3

The

Reason

for

Interest in

the

Study

All

the

factors

mentioned above

have

led

to

heavy

investment in

electronic

publishing

by

newspaper production management.

Considering

the

tight

schedule and

the

number of pages

involved in

daily

newspaper

production,

the

speed of

the

process

from

editorial

to

distribution is

crucial.

The

speed of

the

imagesetter

is

an essential

factor in

production

turn-around time.

Although

trade

publications such as

The

Seybold Report

on

Publishing

Systems

and

Color

Publishing

have

publishedspeed

tests

of

high-resolution

PostScript

imagesetters,

most studies give

only

vague

reasoning for

the output resolution

chosen

for

a given

test.

In

a

Seybold

Report,

the

resolution

for

newspaper

tests

was

between 1,000

and

2,000

spi,

with

the

justification

that

"...not

many

people

would print newspaper pages at

anything

higher

than

that."3

The

reason

for

interest in this

study

is

to

find

a

way

to

speed

up

the

imagesetter

output

time

even

further,

independently

from

technical

constraints

suchas

processing capability

of

the

raster

image

processor,

laser

arrangement

obtain areproduction

that

is

visually

not

distinguishable

from

higher

resolution

output,

the

imaging

ofseparationscan

be

optimized

to the

shortest

time

Endnotes

for

Chapter 1

1"New

Color

Ink Book

Due

in

1993."

American Newspaper

Publishers

Association,

Special

Supplement

to

Tech News (December

1990): 1

2"PostScript

Speed

Tests:

Hyphen, Harlequin, RIP30, Emerald,

etc.",

The

Seybold Report

on

Publishing

Systems

20

no.10/11

(February

25,

1991):

5

Chapter

II

Theoretical Background

2.1

Electronic Halftone Reproduction

Electronic

halftone

reproduction consists of

three

major steps:

scanning

(input),

editing

and

/or

manipulation,

and

output,

normally

by

means of an

imagesetter.

The

primary

difference

of electronic

halftone

reproduction compared

to

conventional

halftone

reproduction

is

the

process

whereby analog

image

information

(density)

is

converted

into digital information

(brightness

levels),

manipulated,

and

then

converted

back

to

analog

information

by

exposing films

on an

imagesetter.

Conventional

halftone

reproduction

is

a

purely analog

process.

2.1.1

Input

To

accurately

reproduce an

image,

there

should

be

no

information lost

in

the

conversion

from

analog

(continuous)

to

digital

(discrete) form,

neither

in

number of

tones

nor

in

spatial

detail.

Digitizing

an

image is

aprocess

whereby

samples

of aphotographare

taken

atspecific

locations

within

it. Each

sample

is

givena numeric value

based

on

its

brightness,

ranging from

black

to

white.1

is

oftenreferred

to

as a picture

element,

or

pixel,

because

of

its

representationof a

discrete

elementof

the

digital

image."2

For

halftone

_reproduction

purposes, the

conversion of

the

continuous

tones

into

256

discrete grey

levels

per separation

is

usually

sufficient

to

represent

the

brightness

of an

image

accurately.3

The

number ofsamplesper

image

area

determines

the

spatial resolution of an

image. Resolution is

a

term

used

for

describing

the

limitation

of

the

digitizing

process.

The higher

the

resolution or

sampling

rate, the

closer a

digital image

will represent the original.

According

to the

Nyquist

Criterion,

also

known

as

the

Sampling

Theorem,

".

..to

fully

represent

the

rate of

brightness

change,

or

detail,

in

anoriginal

image

wemustsample

it

at a rate at

least

twice

as

high

as

the

highest

spatial

frequency

of

the

detail."4

The

"detail"

in

a

halftone

reproduction

is

the

individual

halftone

dot,

and

the

spatial

frequency

of

the

halftone dot is

given

by

the

screen ruling.

As

an

example,

if

the

chosen screen

frequency

is 85

lines

per

inch,

there

are

85 halftone

dots

per

inch

recorded onto

film

or paper.

In

order

to

comply

with

the

Nyquist

Criterion,

the

scanning

resolution

for

an

image

has

to

be

chosen

in

such a manner

that

the

resulting

image file

has

twice

as

many

pixels per

linear inch

than

halftone

dots

after output.

If

the

pixelcount

is

too

low,

aliasing may

occur,

whichwould

be

seenasamoirepattern

in

the

digitized

image

or,

if

the

pixelcount

is

much

too

low,

as"staircasing"

(see

Figure

l).5

There have been

some

indications

that

the

2

to

1

sampling

ratio might

be

excessive and a ratio

between 1.7

and

1.4

to

1

might

be

sufficient

for

most

reproduction purposes.

A lower

sampling

ratio would

decrease

the

image file

size,

thereby

further

accelerating

the

editing

and

processing time for

a given

system.

As

there

have

not

been

any

conclusive studies published

by

the

time

this

8

according

to the

Nyquist Criterion

to

eliminate

any

decrease

in image

quality

due

to

incorrect

sampling.

ump

IflHlUlf

100

ppi

20

ppi

Figure

1

-

Visual

effect of correct and

incorrect

sampling

ratios.

The

image

on

the

left

side was sampled

according

to the

Nyquist

criterion.

The image

file

Street Cafe

contains

100

pixelsper

inch

(for

a screen

frequency

of

53 lpi).

The image

to

the

right

was

undersampled,

the

image

file

contains

20

pixels

per

inch.

2.1.2

The Histogram

Although

image

manipulationand

editing

capabilitiesofelectronic

halftone

reproduction systems werenot part of

this study,

there

are some conceptswhich

have

to

be

introduced

as

they

werepartof

the

image

file

preparation

for

output.

Digital

image

editing

and manipulationare

based

on

the

fact

that

various

image

characteristicsare

described

numerically.

As

mentioned

above,

each pixel [image:24.530.70.462.117.434.2]

its

brightness

value.

In

caseof acolor

image,

each pixel

has

more

than

one

grey

valueassociated with

it,

depending

on

the

amount of channels

the

image

contains

(three

channels

for

red,

green and

blue;

or

four

channels

for

cyan,

magenta,

yellow and

black).

By

convention,

if

a particular pixel

has

anumerical

value of

0,

the

visualappearanceof

that

pixel

is

black;

if

the

value

is

255,

the

appearance

is

white.

Simple image

editing

functions like

overall

brightness

or contrast changes are

executed

by

simple mathematical

functions. As

an

example,

if

an

image

should

appearoverall

darker,

a specific value

is

subtracted

from

each pixel value

(see

Figure

2).

In

case of a contrast

change,

each value

is

multiplied

by

a

factor.

If

the

factor is

smaller

than

1,

the

contrast

is

decreased;

if

the

factor is

greater

than

1,

the

contrast

is

increased.

These

most

fundamental image

processing

operations

arecalled point

operations,

as all pixelsaremodifiedindividually.6

normal

[image:25.530.70.461.380.627.2]

-30

Figure 2

-

Brightness

_{change of}

the

image Woman

when

subtracting

30

from

10

A

tool

oftenused

to

assess

the

brightness

_{and contrast}attributes of an

image

is

the

image

histogram.

In general,

a

histogram is defined

asa

frequency

distribution

graphof aset of numbers.

An

image histogram

is

a graph which

contains

brightness

valueson

the

horizontal

axis

(0

to

255),

and

"number

of

pixels"

on

the

verticalaxis

(see Figure

3).

A

histogram

is

aneasy-to-read representationof

the

concentrationofpixels versus

brightness

in

an

image. It

providesan

immediate

analysis whether

the

image is

basically

dark

or

light

and

high

or

low

contrast.7

pixel values

Figure

3

-

Histogram

[image:26.530.106.404.262.603.2]

11

Adobe

Photoshop,

an

image

manipulationand

editing

software

for

the

Apple Macintosh

platform,

uses

the

histogram

representation

to

allow

the

operator

to

manipulate

highlight,

midtone andshadow placement.

Another

important

concept

in

desktop

publishing is

the

conversion

from

additive

to

subtractive color space.

There

is

a

difference

in

color gamut

between

the two

systems.

Additive

systems,

such as

CCD-scanners

and

monitors,

record

or

display

colors as a combination of

red,

green and

blue. On

the

other

hand,

reproductions are printedwith

cyan, yellow, magenta,

and

black inks. To

be

able

to

previewon a monitor

how

an

image

will reproduce-so-called"soft"

proofing-the

monitor

has

to

be

calibrated

to the

reproduction system.

A

simple

mathematical conversion of

brightness

values,

based

on

the

concept

that

red,

green and

blue

are

complimentary

colors

to cyan,

magentaand

yellow,

does

not

take

into

consideration

the

spectralcontaminationsof real

inks

and

the

black

printer,

and

is

therefore

not applicable.

Consequently,

conversion algorithms

have

to

be

established

that

calculate

brightness

values

for

the

black

separation,

depending

on

the

"strength"of

the

black

printer and

the

overall

brightness

value

of

the

pixel.

These

algorithms

usually

differ from

onesoftwaremanufacturer

to

another.

The

"original"

images

used

in

this

study

were

digitized

CMYK

files,

which

were converted

to

RGB

and

then

back

to

CMYK. As

true

color rendition was not

part of

this study,

no special considerations were given

to

the

conversion

process.

The Adobe

Photoshop

separation

function

wasused

to

convert

the

RGB

files

into CMYK. Each

separation was

then

treated

individually

to

adjust

for

press specifications.

Additionally,

there

was nocalibratedmonitor available

for

12

2.1.2

Output

The

device

used

to

expose electronic

halftone

separationsonto photographic

film

or paper

is

called

imagesetter.

A

newer generationof

former typesetters,

an

imagesetter

can

be described

asasophisticated

laser

printer,

whereby

photographic

film

orpaper

is

exposedwith

laser

beams in

agrid structure.

These

exposure"marks" are often referred

to

as

spots,

dots

ormachine

pixels,

but

for

the

purposeof

this

document,

the term

spot will

be

usedexclusively8

The

number of spotsexposedover a certain

image

area

define

the

resolution of a

device,

hence

the term

spotsper

inch

(spi)

for

describing

imagesetter

output

resolution.

The

outputresolution an

imagesetter

can achieve

is

device

dependent,

primarily

on

the

diameter

of

the

laser beams

and

their

array.

Most

imagesetters

on

the

market

today

have

the

option of

selecting

different

output

resolutions,

usually

between

approximately

400

(600)

up

to

2400

(3600)

spi.

The

spot size

has

to

be

adjusted

according

to the

resolution

setting

chosen.

One

method

is

to

adjust

the

diameter

of

the

laser

beam

by

moving it

closer

to

or

further

away

from

the

film,

or

by inserting

different lenses

between

the

laser

and

the

film.

Another

technique

is

to

vary

the

intensity

of

the

beam,

but

this

method cancause

problems

maintaining

consistent

dot

quality.9

A

low

intensity

beam

may

not

expose

the

photographic material

sufficiently

to

createanadequate

density

necessary for

correct plate exposure.

As

the

laser

beam's

intensity

peaks

in

the

middle and

decreases

to

the edges,

the imagesetter

spots

have

to

overlap slightly

to

expose asolid

density

halftone

13

halftone dot

would containunexposed

areas,

which would result

in

a

decrease

of

dot

quality,

not

to

mention

uncontrollable

variationsof areacoverages

(dot

percentages).

Considering

agiven

file

andagiven

system, the

speedwith which an

imagesetter

canexpose

film

or paper

is

directly

related

to

the

outputresolution.

The imagesetter

used

for

this study, the

Linotronic

530,

offers eight

different

addressableresolution

settings,

ranging

from 423

spi

to

2540

spi.

The

speed

for

output of aspecific

file

at

423

spi

is

givenas

47.4

inches

per

minute, the

speedat

2540

spias

5.3

inches

perminute.10

Note

that the

output speed at a given

resolution will

vary,

depending

on

the

complexity

of

the

output

file.

In

electronic

halftone

reproduction,

a cluster of

imagesetter

spots creates a

halftone

dot.

Depending

on

the

imagesetter

outputresolutionand

the

screen

frequency,

the

number of spots used

to

create one

halftone dot

varies.

More

spots allow

for

finer increments

in dot

sizes.

If,

for

example,

four

spotsareavailable

to

image

one

halftone

dot,

five different dot

percentage values arepossible: no spot

exposed

leaves

the

area unexposed

(0%

dot),

onespot exposed results

in

a coverage ofonequarter of

the

area

(25%

dot),

etc.

(see

Figure

4).

As

a

consequence,

screen

frequency

and output resolution

have

a

direct influence

on

the

numberof

grey

levels

visibleand can

be

calculated

using

the

following

equation:

(Resolution

*

Screen

Frequency)2₊

1

=

Grey

Levels

11

14

5

Bi W

0

spot

1

spot

2

spots

3

spots

4

spots

Grey

Level 1

Grey

Level

2

Grey

Level 3

Grey

Level 4

Grey

Level 5

Figure

4

-

A 2x2

spotmatrix per

halftone dot

results

in

a

total

of

5

grey

levels.

The

more

imagesetter

spots used

to

create one

halftone

dot,

the more

grey

levels (or

colors)

a

halftone

reproduction will contain.

Considering

the

resolutions chosen

for

this experiment,

and

the

given screen

frequency

of

85

lines

per

inch,

the

theoretical

number of

grey levels

each separationcontains can

be

calculated

according

to the

formula

above.

Table 1

-

Number

of

grey levels

for

each separation

depending

on

the

output resolution.

Resolution

Grey

levels

Number

of

Colors

(CMYK)

846

spi

100

100

million

1016

spi

144

430

million

1270

spi

224

3.5

billion

1693

spi

(398)

256

(25)4.3

billion

As

can

be deduced from

Table

1,

the

fewer

grey levels

a separation

contains,

the

more

limited

the

color rendition of

the

reproduction

becomes. Note

that the

number of colors are

only

theoretical

figures,

calculated

by

multiplying

all

15

separations

(i.e. 100x100x100x100

=

100

million) to

obtain all possible combinations.

In

reality, the

rangeofcolorsareproductionwillcontain

is

severely limited

by

process constraints such as

highlight

andshadow placement which are never at

0

or

100

percent,

the

black

separationwhich

is

not a

full

tonal

separation,

and

the tonal

rangeof

the

image

itself. In

addition,

independently

from

the

imagesetter

resolution, the

brightness

resolution of

the

digitized

image

will

limit

the

maximumnumber of

grey levels

orcolorsobtainable.

The images

used

in

this

study have

a

brightness

resolution of

8

bits

per pixel.

In

this

case,

the

theoretical

number of

398

grey levels

for

an output resolution of

1693

spi

is

not

achievable,

as

the

image itself is limited

to

2^or

256

grey

values per channel.

Another

consideration of

imagesetter

output resolution

is

the

halftone

dot

shape.

A

halftone dot has

a

better

defined

shape

if

morespotsare used

to

image

it.

If

fewer

spots are

used,

the

circumferenceof

the

dot looks

jagged.

Although

electronically

created

halftone dots

are so-called "hard"

dots

and are

less

likely

to

loose

their

shape

during

plate

exposure,

ink

spreading

or

dot

gain

during

printing becomes

unpredictableand

poorly defined halftone dot

shapes

may

result

in

considerable color shifts.

i

1

IH

!

\

i

16

It

remains

to

be

seen

if

the

above mentioned constraintsof

low

output

resolution-number ofcolorsand

dot

shape-are

important factor

in

newspaper

image

reproduction,

considering

all

the

other

limiting

factors

suchaspoor

registration,

inferior

paper

quality,

coarsescreen

frequency

and

low

ink density.

By

letting

anaudience

visually

evaluate

the outcome,

the

hypotheses

stated

in

Chapter HI

can

be

proven or rejected.

2.2

Statistically

Valid Methods

for

Visual

Evaluation

of

Quality

The

idea

that the

human

sensory

system can

be

used

to

measure a physical

quantity

goes

back

to the

German

physicist

Gustav

Theodor Fechner.

He

established

that

it is

possible

to

develop

".

..anexact

theory

of

the

relation of

body

andmind."12

Fechner's

_{controversial}

law

_predicts

that

_{equalstimulus}

ratios elicit equal

sensory

differences.13

Consequently,

visualpsychophysics

is

concernedwith

"...the

study

of

lawful

stimulus-response relationships and

theoretical

concepts about

explanatory

mechanisms."14

Physical

sciences,

sometimes referred

to

as

the

"exact"

sciences,

arenot

particularly

controversial.

They

depend

on an

instrument

to

measurea

physical quantity.

As

an

example, two

people

measuring

the

length

ofanobject

will

probably

get

the

same

result,

as

the

calibrationof a ruler

is

universally

the

same.

In

other

words,

a meter was once

defined

as

the

length

of astandardmetal

bar in

Paris,

and

any

instrument

capableof

measuring length

in

the

metric

system

incorporates

the

length

of

this

standard.15

On

the

other

hand,

the

measurement or

scaling

ofsubjective qualities

is

17

inherently

private,

a person can

only

evaluateon

the

strength of

his

or

her

own

sensation.

If

one observer

insists

thatacolor

is

ten

times

as saturated

than

another

color,

although

they

nearly

match

for

another

observer,

there

is

no

ground

to

doubt

either judgement.16

Although

a color can

be

specified as

".

..the

matching

of spectral wavelength withadditive amountsof

three primaries"17,

the

appearanceof thatcolor

".

..dependson

many

unspecified parameters suchas

luminance,

area,

retinal region

stimulated,

duration

of

presentation,

state of

adaptation of

the

eye,

and

the

influence

of

surrounding

colors."18

Different

methods

have

been

established

to

estimate

sensory

magnitude.

Psychophysical

methods assume

that there

is

a

direct relationship

between

stimulus and response.

For example,

if

the

intensity

of a

light bulb is

turned

down,

".

..thesensation of

brightness clearly

decreases

monotonically

withthe

diminution

of

the

physical

intensity

of

the

light.

Consequently,

there should

be

no

difficulty

in

establishing

an ordinalscale of

brightness

as a

function

of

physicalintensity"19

Psychometric

methods,

as opposed

to

psychophysical

ones,

areconcerned

with

the

scaling

of stimuli which

do

not

have any

measurablephysical

quantities.

The

stimuliare rated

according

to the

reaction

they

produceon

human

observers.

In

other

words,

psychometricmethods give

indications

about

responsedifferences.20

In

this

study, the

stimuliprovided

to

the

observerswere

images

with

different

outputresolution.

To

test

the

hypothesis,

the

observers

had

to judge the

quality

of

the

reproduction,

which

is

asubjective

criterion,

as

it

depends solely

on

the

observers

definition

of

quality

and

is independent from

the physical specifications of

the

reproduction.

There

are

three

psychometricmethods established

that

providea

18

ofpaired

comparison,

and

the

methodofcategories.

When

using

the

rank order

method, the

observer

is

asked

to

order

the

stimuli

according

to

a specified

criterion.

The

result

for any

particular

observer,

by

definition,

will

be

an ordinal

scale.

This

method

is

useful

if

the

differences

of

the

stimuli

is

relatively

apparent

and

the

number of stimuli

is

not

too

large.21

The

method chosen

for

this

study

to

measure

the

existence of a visual

difference

between

the

reproductions

is

the

pairedcomparisonmethod.

Described

formally

the

first

time

by

Louis

Leon Thurstone

(1927)

in

the

law of

comparative

judgments,

"..

.theobserver's

task

in

the

methodof paired comparison

is

to

discriminate between

two

stimuli..

It is

".

..basedon the notion

that the

proportion of

times

stimulus

A

will

be judged

greater

than

stimulus

B

is

determined

by

the

degree

to

which sensation

A

and sensation

B

differ".23

In

other

words, the

proportion of observers

judging

onestimulus

to

be

greater

than

the

other gives a

direct

indication

of

how

the

attributesunder

study

differ. The

stimuli

in

this

study

were

the

images

reproduced with

different

output

resolution.

If 95%

of

the

observers preferred oneoutputresolution

to

another,

one could

safely

assume

that there

is

a real

difference

in

quality

of

the two

images.

If,

however,

the

images look

the

same

to the

observers,

the proportion of

response should

be

around0.50.24

The

methodology

of paired comparison as

it

applies

to this

experiment

is described in

section

4.8.

The

paired comparison method works

best

when

the

number of stimuli

is

low

and

the

stimulus

differences

are

very

small

(in

fact,

when

the

differences

are

not small

enough,

the

method

does

notwork well).

By forcing

the

observers

to

19

The

method

of

categoriesrequiresobservers

to

sort stimuli

into

a

limited

numberof

categories,

usually

having

useful

labels. As

an

example, the

labels for

this

experimentcould

have been

excellent, good,

passable,

and

bad. This

method

is

advantageous

if

the

number of stimuli

is large. The

numberof categories used

depends

on

the experiment,

seven

is

usually

considered amaximum.26

The

choice ofwhich method

to

use

is entirely up

to

the

experimenter.

It

usually depends

on

the

degree

of precision

needed,

as well as

the

time

and cost of

the

experimentation.

In

any

case,

a psychophysical experiment

has

to

be

Endnotes for Chapter

2

Gregory

A.

Baxes,

Digital

Image Processing.

(Englewood

Cliffs,

N.J.:

Prentice-Hall,

1984;

reprint,

Denver,

CO:

Cascade

Press,

1984):

22

2(lbid,

22)

3Caren

Eliezer,

"Color

Screening

Technology:

A Tutorial

on

the

Basic

Issues,"

The

Seybold Report

on

Desktop

Publishing

6,

no.

2

(October

2,

1991):

16

.

4(Baxes 1984, 23-24)

5(lbid,

24)

6(Ibid,

38)

7(lbid,

32-33)

8Jim

Hamilton,

Digital

Halftone

Dots

(Hauppage,

NY:

Linotype-Hell

Company,

1991),

partnumber

3060,

Technical Information:

1

9(Eliezer 1991, 17)

10"Linotronic

530,"

Linotype

Company

(1990):

2

"(Eliezer

1991,

16)

12E.

G.

Boring,

What

is

Science?

(J.

R.

Newman,

ed.,

New York:

Simon

and

Schuster,

1955)

as quoted

in James C.

Bartleson,

Franc

Grum,

ed.,

Optical

Radiation Measurements

(Orlando:

Academic

Press, Inc., 1984),

vol.

5,

Visual

Measurements:

335-336

13James

C.

Bartleson,

Franc

Grum,

ed.,

Optical Radiation

Measurements

(Orlando: Academic

Press, Inc., 1984),

vol.

5,

Visual Measurements: 338

21

14(Ibid,

336)

15(Ibid,

338-340)

16(lbid,

339)

17(Ibid,342)

18(Ibid,

342)

19(lbid,

357-358)

20(lbid,

358)

21(lbid,359)

22George

A.

Gescheider,

Psychophysics

-Method, Theory,

and

Application,

2d

ed.

(Hillsdale,

N.J.,

London: Lawrence Erlbaum

Associates,

1985):

147

^(Ibid,

147)

24(lbid,

147)

^(Bartleson,

Grum

1984, 485)

26(Ibid,

359)

Chapter

III

Hypotheses

The

visual

quality

of

images

reproduced

in

newspapers

is

not

dependent

on

the

imagesetter

output resolutionabove a certain

limit

for

agiven set of print

parameters.

For

offset newspaper

printing

on consolidated newsprint at a screen

frequency

of

85

lpi,

the

resolution

limit

lies between

1,000

and

1,200

spi.

Chapter

IV

Methodology

4.1

The

Choice

of

Image Resolutions for

the

Study

As

mentioned

in

section

2.1.2,

the

screen

frequency

of a reproduction and

the

imagesetter

outputresolution

determine

the

number of colors an

image

can contain.

Lowering

the

outputresolution willresult

in

fewer grey levels

per

separation,

and

consequently

fewer

colorsper reproduction.

To

make this

study

valid

for

practical

application,

it

was moreobvious

to

vary

the

imagesetter

output resolution

than the

screen

frequency.

The

screen

frequency

of reproductions

for

a given newspaper

is

usually

predetermined

by

press

characteristics such as print

method,

ink

and paper quality.

On

the

other

hand,

most

imagesetters

on

the

market

today

offer arangeof addressableoutput resolutions.

It

is left

to the

prepress operator

to

choose

the

resolution

best

suited

for

the

printapplication.

In

this

study,

the

screen

frequency

was

kept

constantat

85

lpi

(see

section

4.4).

The hypothesis

is based

on theassumption

that

there

should

be

a

decrease

in

image

quality

if

the

outputresolution

is

too

low. At

a certainadaptation

level,

the

human

eye

is

able

to

distinguish

128

to

256

grey levels

simultaneously.

Consequently,

anoutput resolution

between

1,000

SPI

(139 grey levels

per

24

separation)

and

1,200

spi

(200 grey levels

per

separation)

should

theoretically

be

sufficient

to

obtainagood

image

reproductionat

85 lpi.

Any

output resolution

higher

than

that wouldnotgivea

distinguishable increase

in image

quality,

as

the

human

eye

is

incapable

of

resolving

the

differences. On

the

other

hand,

any

output resolution

lower

than

1,000

spi

could

theoretically

createartifacts

in

the

reproduction.

To

test this

theory,

output resolutionswhich were considered"normal"and

outputresolutionswhich were considered

too

high

and

too

low had

to

be

included

in

the test

matrix.

Besides

the

normal

1,000

and

1,200

spi

imagesetter

output

resolutions,

only

one

"high"

and

"low"

resolution could

be

considered

due

to

sizeconstraints.

The

next

higher

than

1,200

spiresolution

setting

for

most

imagesetters is approximately

1,600 SPI,

the

next

lower

than

1,000

SPI

setting

is

approximately

800

spi.

The

final

output

resolutions,

846 spi, 1016

spi,

1270

spiand

1693 spi,

were

determined

by

the

actual

imagesetter

Linotronic 530

used

to

output

the

films (see

section

4.5).

4.2

The Choice

of

Images for

the

Study

The

numberof

images

that

could

be

used

in

this

experimentwas

physically

limited

by

the size of

the test

matrix

(22.75"

x

30")

and

the

number ofoutput

resolutions

to

be

tested

(846

spi, 1016

SPI, 1270

SPI,

and

1693

spi).

The images had

to

be carefully

chosen

to

represent awiderange of

image

categories.

The

four

images

used

in

this

study

come

from

asetof six

SCID

(Standard

25

continuous

tone

color

images destined for hard

copies madewith

proofing

or

printing

processes.

The

images

were scannedon a

Dainippon

SG-608

high-performance color

scanner,

andstoredonmagnetic

tape

in

CMYK

format

witha spatialresolutionof

2560

pixels

(long

side)

times 2048

pixels

(short

side).

The

brightness

resolution

is 8

bits

per

pixel,

or

256 levels.

The data

format

is

based

on

the

ANSI

IT8.1-1988

"User Exchange Format for

the

Exchange

of

Color Picture

Data

between Electronic Prepress

Systems

via

Magnetic

Tape"

to

ensure

compatibility

of

the

color

image

data,

and

data

transfer

between

different

output systems.1

Due

to test

matrix size

constraints,

not all six

images

could

be

used

for

this

study,

and still

be

reproducedat acceptable

image

size and

in

all

four

chosen

outputresolutions.

Two images

were

eliminated,

the characteristicsof other

four

images

used

for

the

study

are

described in Table

2.

Table

2

-

Image

characteristics of

the

four images

used

in

the

study.

Image

name

Characteristics

Woman

Low-frequency

image

(gradual

tonal

increase

from light

to

dark),

allows

for

evaluation of

the

reproductionof

human

skin.

Street Cafe

High-frequency

image

withcomplicated

geometric patterns and

shapes,

allows

for

evaluation of

the

reproduction of

fine

detail.

Fruit

basket

Low-key

image,

allows

for

evaluation of

the

26

Table

2

-continued

Image

name

Characteristics

Bicycle

High-key

and

high-frequency

image,

allows

for

evaluationof

the

reproductionof

highlight

to

midtone

gradation as wellas

image

sharpness.

4.3

The Design

of

the

Test

Matrix

The

test

matrix was

designed

on an

Apple Macintosh

personal

computer,

using

QuarkXPress

3.0

page

layout

software.

The

size of

the test

matrix was

determined

by

press

specifications,

the

press

having

a

total

paper width of

30

inches

and a repeat

(cut-off)

length

of

22.75 inches.

The

matrix

had

to

be

designed

in

such a

way

that

the

space

is

optimally

utilized,

allowing

for

normalsize

image

reproduction and

easy assembly

of

separations with

different

output resolutions.

Test

targets

to

measuresolid

ink

density,

UGRA

wedges

to

measure plate

exposure,

andresolution

targets

consisting

of

Fresnel

zoneplates

(see

page

34) had

to

be included

in

the

matrix.

The

resulting

layout

(see

Appendix

A)

contained

16

images. Each

column

consisted of

the

four different

types

of

images

reproducedwith

the

same output

resolution.

The dimension

of

the

images

came out

to

be

4.4"

x

5.5",

leaving

room

at

the

bottom

and

the

sides

for

test targets

and

title information.

The four

files

sent

for

output were

basically

identical,

except

for

a

letter

at

the

bottom

of

the

images

indicating

the

output resolution

(A:

846 spi, B: 1016 spi,

27

"white

space"

around

the

sides

to

facilitate

stripping.

The

first file (846

spi)

additionally

contained

the

title information.

The Fresnel

zone plates

(see

section

4.8)

resolution

test target

was a

PostScript

program written

by

Professor Frank

Cost

and

imported

into

PageMaker 4.0

page

layout

softwareon an

IBM DOS

personal computer.

The

EPS

file format

was not

compatible with

QuarkXPress,

therefore

the targets

could not

be imported into

the

layout. The

target

wassent asa separate

PageMaker

file

(for

Macintosh),

to

be

imaged

with

the

sameoutput resolutions

than

the

image files.

The image

files,

discussed in

section

4.2,

and

the

page

layout

files

were stored on a

SyQuest

44MB

removable

disk.

4.4

The

Preparation

of

the Images

for Output

As described

in

section

4.2,

the

original

image

file

data

was stored on magnetic

tape

in CMYK

format.

To be

able

to

import

the

files

asraw

data

(binary

data)

into

Adobe

Photoshop

2.0,

the

image

editing

software used

for

this study,

the

images

had

to

be

converted

to RGB. The

conversionwasexecuted

using

separation

algorithms

developed

by

Mr. J. A. Stephen

Vlggiano from

the

RIT Research

Center.

After

importing

the

RGB

files into

Photoshop,

the

images

were resampled

according

to the

Nyquist

criterion.

Considering

the

chosen screen

frequency

of

85 lines

per

inch

and

the

physical size of

the

images

of 4.4"

x

5.5",

the

image

files

were sized

down

to

748

x

935

pixels.

The

choice of

85

lines

per

inch

as screen

frequency

was

for

the

following

28

offsetnewspaperprinting.

Because

the

study

could

only

evaluate

the

effect of

output resolution onone

frequency,

85

lpi

was a

logical

choice.

Second,

press

specifications which

had

to

be included

in

the

preparation of the

images

were

only

available

for

85

lpi

screen

frequency.

After

resampling,

the

images had

to

be

converted

to

CMYK

again so

that

highlight

and shadow placement aswell as

dot

gain specifications could

be

included for

eachseparation.

Photoshop

2.0's

separationalgorithms are

transparent to the

operator,

except

for

the

choice of

three

black

printers.

As

true

color

rendition,

i.e.

matching

the

reproduction with

the

original,

wasnot part of

this study,

no

further

consideration was given

to the

separation

process,

and

the

medium

black

printer

setting

was chosen.

Each

separation

had

to

be

adjusted

for

highlight

andshadow

dot

placement

as well as

dot

gain.

The

most convenient

way

in

Photoshop

2.0

to

adjust output

values

is

under

the

"level"

command,

which allows

histogram

compression and

extensions

for

each channel

(or

separation).

Input Leuels:

0

1.00

255

Output

Leuels:

0

255

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OCM

OVOK

O

Master

Figure

6

-

User

interface

of

"level"

command

in

Photoshop

2.0

(Image

Bicycle,

29

A Kodak

Customized

Color

Analysis

2_executed

for

the

Goss

Community

Newspaper

Printing

Press

which was used

to

print

the test

matrix gave valuable

informat