Production Sensitometric Testing of Lithographic Films Correlated with Customer Quality Acceptance

Rochester Institute of Technology

RIT Scholar Works

Theses

Thesis/Dissertation Collections

4-30-1962

Production Sensitometric Testing of Lithographic

Films Correlated with Customer Quality

Acceptance

Lawrence Albertson

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.

Recommended Citation

Lawrence

P.

Albertson

Abstract

Various

methods of

production

sensitometric

testing

of

lithographic

films

are

investigated

to

establish correlation

between

a

testing

parameter and customer acceptance of

line

copy

reproduction

in

the

field.

The

chosen

parameter,

"gamma,"

is

compared

statistically

for

acceptable and unacceptable repro

duction

based

on

field

appraisals.

Results

indicate

that

no

correlation exists

between

the

chosen

testing

parameter and

field

acceptance.

Information

is

also obtained

concerning

the

development

and exposure conditions which yield acceptable

line

copy

reproduction

in

the

field.

Introduction

It

is

desirable

in the manufacturing

of all photo-sensitive

materials

to

have

correlation

between

production sensitometric

parameters and customer

acceptability

of

the

product.

In

other

words,

the

ideal

situation

is

one where customer acceptance

is

predicted

by

parametric values obtained

during

production.

In

the

manufacturing

of most photographic materials

there

is

at

least

some

degree

of correlation

in

this

respect.

Many

materials

have

production sensitometric systems which correlate

very

highly

with consumer acceptance.

Photographic

papers are

generally

very

good examples of

this

type

of situation.

However,

Graphic

Arts

materials,

in

particular

high-contrast

lithographic

films,

seem

to

lack

this

correlation.

The

litera

manufacturers

certainly have

production sensitometric systems

in

effect.

Whether

or not

these

systems

have

any

correlation with

customer

acceptance

is

not

known.

An

Investigation

was made

to

obtain

Information

in

th6

Graphic

Arts

field

of

line

copy

reproduction

concerning

the

degree

of

correlation

between

a production sensitometric parameter and

customer acceptance of

the

product.

Also

of

interest

were

the

conditions of exposure and

development

under which

line

copy

re

production

is

acceptable.

Chosen

for

this

experiment were

three

methods of

measuring

the

"gamma" of

lithographic

films

taken

from

published material

in the

field.

It

is

not

known

definitely

that

these

methods are

actually

used

in.

industrial

applications.

It

should

be

noted

that

"gamma"

in

reference

to

lithographic

films

does

not

have

the

conventional

meaning

of

the

slope of

the

straight-line

portion of

the

characteristic

curve,

but

rather

the

slope of

a

line

connecting

two

arbitrarily

defined

points on

the

character

istic

curve.

It

is

in

this

latter

sense

that

the

term

"gamma"

will

be

used

in

this

paper.

An

explanation and

illustration

of

the

three

methods of

measuring

gamma

follows;

V) Z

D-

0.1

net

LOG EXPOSURE

Fig.

1

Ansco

Method

(%).

The

average

gradient

(gamma)

is

obtained

by

con

necting

the

points with

densities

0.1

and

2.5

net on

the

characteristic curve

and

measuring

the

slope of

the

con

necting

straight

line.

If

this

line

intersects

the

characteristic curve

at a

density

below

2.5

net,

it

is

tilted,

using

the

point with

density

0.1

as a

pivot,

until

it

becomes

a

tangent

to

the

characteristic curve.

In

this

case,

the

tangent

slope

is

tk

D

=

3.

net

0_

/

//

Ul

1

t

1

ll l

I

y

D

=

0.2

"*- _net

-.

-

3

-Fig.

2

Haloid

Xerox

Method1

(

?H

)

.

Gamma

is

obtained

by

connecting

the

points with

densities

0.2

and

3.00

net on

the

characteristic curve and

measuring

the

slope of

the

connecting

straight

line.

LOS EXPOSURE

t

CO r UJ L06

EXPOSURE

Fig.

3

Kodak Method

(?K).

The

effec

tive

contrast

(gamma)

is

obtained as

follows:

Locating

a point

0.1

above

fog

(first

point);

locating

a second

point,

0.4

log

E

to

the

right of

this

point;

drawing

a vertical

line

so

that

it

intersects

the

curve at a

third

point

if

the

density

is

higher

than

2.4,

the

third

point

is

given

by

the

point

corresponding

to

density

2.4

on

the

characteristic

curve;

the

slope of

the

lines

connecting

points

1

and

3

is

the

effective contrast.

Experimental

Procedure

Basically

the

procedure

for

this

experiment

involved

photo

graphing

a

test

copy

containing

representative samples of various

line

originals;

exposing

sensitometric

strips;

and

comparing

statistically

gamma values

for

acceptable negatives with gamma

values

for

unacceptable

negatives,

negative

acceptability

being

determined

by

field

appraisal.

To

test

the

three

methods of gamma measurement as

outlined

above,

two

films

known

to

have

different

performance character

istics

in

the

field,

Kodak

Kodalith

Ortho

Type

3

and

Haloid

-*-The names attached

to

the

methods

indicate

the

source of

the

[image:5.558.38.507.87.472.2]

Halolith,

were selected.

Kodak Kodalith

Developer,

which

is

widely

used

in field

applications with

the

above

films,

was

chosen

for

developing

all negatives and sensitometric strips.

The

test

copy

was composed of representative

line

copy

samples suggested

by

Graphic

Arts

field

personnel

located

with

various

printing

_{establishments}

in

Rochester.

Included

in

the

test

copy

were samples of register

marks,

typing

material,

vari-type,

phototype,

pen and

ink

drawings,

serifs,

letterpress,

and

a

resolving

power chart.

In

attempting

to

encompass

the

range

of conditions which produce acceptable negatives an exposure

time-development

time

matrix was

designed using

practical

limitations

of

both

variables as extreme values.

Figure

4

shows

the

matrix

form.

o

U-oi

o o. m

47

30

19

12

8

5

li

2

2i

3

4

DEVELOPMENT

TIME

(MH)

Fig.

4

Exposure

time-development

time

matrix [image:6.558.151.413.419.690.2]

-5

-In

order

to

perform

the

statistical correlation a sensi

tometric

strip

was needed

for

each negative.

To

minimize vari

ability,

sensitometric

strips were exposed

in the

camera with

the

negatives.

Thus

each

11

x

14

sheet of

film

contained a negative

of

the

test

copy,

and a sensitometric

strip

exposed

from

a

0-3.0

density,

continuous wedge placed

in

contact with

the

film

in

the

camera.

The

continuous wedge allowed sensitometric curves

to

be

traced

with a continuous

recording

densitometer.

Statistical

considerations

indicated

that

the

matrix should

be

twice

repli

cated

for

each

film,

resulting

in

a

total

of

144

negatives and

144

corresponding

sensitometric strips.

In

exposing

the

negatives and sensitometric strips a process

camera

utilizing

a vacuum

copy

board,

a vacuum camera

back,

an

electric

timer,

and a voltage-regulated

tungsten light

source was

made available

through

Graphic

Arts

Research

and

Development

at

Rochester

Institute

of

Technology.

Although

the

tungsten light

source

did

not

completely

conform

to

practice,

it

offered

distinct

advantages

In minimizing light

source variation and was of con

siderable

importance

in

assuring

consistent results.

The

negatives and sensitometric strips were exposed and

de

veloped as

indicated

in

the

matrix

in Figure

4.

The

matrix was

twice

replicated

for

each

film.

To

minimize

the

effect of

test

time

the

test

order was established

by

use of a

table

of random

numbers.

The

negatives were

then

taken

into

the

Graphic

Arts

field

as

being

either acceptable or unacceptable.

Sensitometric

curves

were prepared

from

the

sensitometric strips

by

use of a contin

uous

recording densitometer.

The

three

methods of gamma measure

ment were

then

applied

to

each sensitometric curve.

Results

The

data

from

the

evaluations of

five

appraisers

in

the

field

appears

in

Figure

5.

Each

of

the

matrices

in

Figure

5

is

a combi

nation of

the

appraisal results

from

the

twice

replicated matrices

for

each

film.

The

numbers

in

the

boxes

indicate

the

number of

times

the

negatives

from

corresponding

boxes

in the

twice

replicated ma

trices

were

Judged

as acceptable.

Since

there

were

two

matrices

for

each

film

and

these

were shown

to

five

appraisers,

the

maximum num

ber

of acceptable appraisals

is

ten

for

each

box

in

Figure

5.

Haloid

Halolith

Film

Kodak

Kodalith

Ortho

Type

3

Film

r-r47

0

1*

2

0

0

0

47

&

30

|19

^12

3

g

8

X u.

5

0

9

4

2

0

0

Hi

>-630 ID

^19

12

0

0

1

0

0

0

0

9

9

10

0

0

0

0

4*

1

0

0

0

0

1

10

0

0

0

0

0

5*

2

₀

₀

₀

1

6

9

₀

3

o o

0

0

0

0

5* 1*

0

0

0

0

6

1

m

5

0

0

0

0

1*

₀

₀

₀

₀

₀

1* 1*

2

2i

3

4

8

DEVELOPMENT

T\ME

6*1*0

Is

li

2

2i

3

4

8

DEVELOPMENT

TIME

(MIN.)

Fig.

5

Appraisal

Data

*The

asteriks

indicate

occurrences of acceptable negative

quality

where gamma values could not

be

obtained

from

the

corresponding

sensitometric strips

by

one or

#ore

of

the

methods of gamma meas

urement.

Comparison

of

the

matrices

in

Figure

5

with

those

in

Figure

6

will point out which of

the

methods of gamma

measurement

[image:8.558.53.504.423.647.2]

Kodak

Kodalith

Ortho

Type

3

Film

(%)

tt

47

tf

N^

UJ

30

2

h

19

lu

12

(D

8-8

>< Ul

5

5.610

7.710

9.245

14.680

4.660

7.890

7.975

9.660

8.140

4.175

7.740

10.065

8.900

4.105

10.000

10.065

9.750

4.215

12.050

3.940

ii

2

2i

3

4

DEVELOPMENT TINAE

(MIN)

8

Haloid

Halolith

Film

(

?A)

U*7

Hi

42.30

Ui

w

5

3.200

4.355

5.060

4.950

3.120

4.440

4.670

4.360

3.020

4.800

4.700

2.840

3.810

4.320

2.800

4.440

2.730

ii

8

Kodak

Kodalith

Ortho

Type

3

Film

(Tfe)

o47

40-30

u_

Il9

2

12

2

8

us

5

2.900

5.450

7.425

9.130

14.925

4.160

7.870

7.945

9.335

8.760

3.810

7.600

9.930

9.130

3.835

9.910.

10.170

10.720

3.875

13.025

3.510

3.385

ii

2

2i

3

4

DEVELOPMENT

TIME

(MIN.)

8

Haloid

Hal

ol

lth

Film

(

7K

)

^47

<n

19

ul a

12

/>

2

8

X

UJ _

3.350

4.535

5.165

5.065

1.800

3.875

4.850

4.050

1.730

4.550

4.450

3.485

1.450

4.370

4.110

1.745

4.220

1.650

4.050

1.050

ii

2

2i

3

4

DEVELOPMENT

TIME

(MIN.)

8

[image:10.558.69.462.99.570.2]

Kodak

Kodalith

Ortho

Type

3

Film

(%)

d47

UJ

HI

30

h9

*12

tn

2

8

x

UJ

6.590

9-560

11.535

17.775

4.790

9.040

10.605

13.860

8.005

4.445

8.750

10.760

9.065

4.245

10.000

9

.

515

9.505

4.340

9.380

4.150

li

2

2i

3

4

DEVELOPMENT

TIME

(MIN.)

8

Haloid

Halolith

Film

(7M)

o

UJ

Ui

47

30

pl9

ul a

12

3

2

8

X Ui r

4.420

5.160

5.135

3.640

4.370

4.795

4.745

3.545

4.830

5.000

3.360

4.635

3.360

li

2

2i

3

4

DEVELOPMENT

TIME

(MIN.)

The

gamma

data

obtained

from

applying

each of

the

three

methods of gamma measurement

to

each sensitometric curve appears

in Figure

6.

As

with

the

appraisal

data,

the

gamma measurements

have

been

combined

from

the

twice

replicated matrices

for

each

film

into

a single gamma matrix

for

each

film

containing

average

gamma values.

There

are no gamma values

for

some

boxes

because

of gross underexposure and/or underdevelopment which prevented

measurements

from

being

made.

There

were also

borderline

cases

where,

because

of

the

cri

teria

for

a particular

method,

only

one gamma value could

be

obtained

for

corresponding

boxes

from

the

twice

replicated matrices

for

each

film.

In

these

cases a

judgment

had

to

be

made as

to

whether

the

situation was a result of error

in

the

experimental

procedure or variation

in

the

process,

in

the

cases of an error

judgment

the

data

was

discarded;

in

the

cases of a variation

judgment

the

single value was

taken

as an

indication

of

the

aver

age value.

Average

gamma values

for both

films

and

the

three

methods

of gamma measurement were calculated

for

acceptable and unaccept

able negatives.

In

all cases

the

acceptable negative average

gamma was a weighted calculation

based

on appraisal

data

each

gamma value

being

used once

in

the

calculation

for

each acceptable

appraisal

(i.e.,

if

a negative was appraised as _acceptable

four

times,

than

the

corresponding

gamma value was used

four

times

in

calculating

the

average value

for

acceptable negatives.

)

Using

the

same

data

in

the

similar

manner,

standard

deviations

(s)

were

also calculated.

Table

I

lists

the

calculated values of average

-9

-Kodak Kodalith

Oftho

Type

3

Film

Haloid

Halolith

Film

acceptable negatives unacceptable negatives acceptable negatives unacceptable negatives

Ic

X

8.873

6.481

4.166

3.039

S

2.131

4.153

0.564

1.651

/a

X

8.857

6.982

4.098

3.947

s

1.780

3.947

0.513

0.974

J,

X

9.698

7.524

4.552

4.304

s

2.771

4.925

0.179

.

0.803

Table

1

The

values

for

average gammas and standard

deviations

of

acceptable and unacceptable negatives were compared

statistically

for

each

film

and each method

to

determine

significant

differ

ences.

An

"f"

test

was run

comparing

variances

(s2)

and a "t"

test

was run

comparing

average gamma values.

The

results of

these

tests

are shown

in

Table

2

and

Table

3.

Kodak Kodalith

Ortho

Type

3

Film

Haloid

Halolith

Film

calculated

11fii

book

"f"2 calculated

11fti

book

"f"

>K

3.789

3.09,<**0.001

8.600**

3.46,*o.01

X

4.918***

4.37,<**0.001

3.608*

2.64,ed0.05

X

**

3.159

3.12,cc0.01

20.156

10.3,OL*0.01

Table

2

"f"

Test

on

Variances

^Duncan,

Ache

son

J.,

"Quality

Control and

Industrial

Statistics,"

1952,

p.

878,

Table

J.

*The

asteriks

indicate

the

values

found

to

be

significant.

One

asterik represents significance with

the

probability

of

being

wrong

one

time

in

20;

two

asteriks,

one

time

in

100;

and

three

[image:13.558.45.496.56.293.2] [image:13.558.32.496.327.691.2]

Kodak Kodalith

Ortho

Type

3

Film

Haloid

Halolith Film

calculated "t"

book

"t"3 _calculated

"t"

book

"t"

>K

1.607

2.31,cC0.05

2.105

2.26,0^0.05

?A

1.246

2.78,oc=0.05

0.435

2.20,ot0.05

>

1.151

2.57,ct0.05

0.892

2.26,eC*0.05

Table

3

"t"

Test

on

Average

Gammas

Analysis

of

Results

From

Table

3

it

can

be

seen

that

there

are no significant

differences

between

the

average gammas of acceptable negatives

and

those

for

unacceptable negatives

for

any

of

the

three

methods

of gamma measurement with either of

the

two

films.

It

can

be

seen

from

Table

2

that

the

variances

(s2)

were all

significantly

different.

From

this

fact

alone

it

appears as

if

this

parameter

may

be

a useful

indication

of customer

acceptability,

rather

than

gamma.

Closer

examination of

the

standard

deviations,

however,

shows

that

the

data

overlaps

for

acceptable and unacceptable

negatives.

Because

of

this

overlapping

of

data

it

would

be

impossible

to

clearly

separate

the

distributions,

and

it

would

therefore

be

unwise

to

determine

the

acceptability

of

the

product

in

the

field

by

this

measurement.

The

fact

that

there

were occurrences of acceptable negatives

where gamma measurements could not

be

made

helps

to

support

the

above analysis.

Further

examination of

this

point reveals

impor

tant

information

and a possible clue

towards

the

solution

of

the

[image:14.558.48.487.80.245.2]

-11

-problem of

lack

of correlation

between

production sensitometric

testing

and customer acceptance of

the

product.

Inspection

of

the

characteristic

curves,

for

the

occurrences of acceptable nega

tives

where gamma measurements could not

be

made,

indicate

one of

the

shortcomings of

the

various gamma measurement methods.

Although

people

in

the

Graphic

Arts

field

maintain

that

a minimum

background

density

of about

2.5

is

necessary

for

acceptable

line

copy

reproduction,

the

sensitometric curves of acceptable nega

tives

indicate

that

this

value could

be

as

low

as

1.8.

It

is

easily

seen

why

two

of

the

methods of gamma

measurement,

7^

andO^

fail

to

measure gammas

for

acceptable negatives with

low

back

ground

densities,

or

in

the

case of sensitometric

strips,

low

maximum

densities,

y^

and

*Vh

require maximum

densities

of at

least

2.5

net and

3-0

net,

respectively,

before

the

methods can

be

applied,

"V.

is

not as

wholly

dependent

on a mimimum value of

Dmax

as

the

other

two

methods,

but

this

factor

is

still

extremely

important

with

this

method also.

A

method of gamma measurement

which

is

going

to

satisfy

the

desired

correlation as stated pre

viously

must,

then,

be

able

to

make

the

measurement

for

the

entire

range of possible maximum

densities

for

acceptable

line

copy

reproduction.

Figure

5

contains considerable

information

concerning

the

range of exposure and

development

conditions which will produce

acceptable

line

copy

reproduction.

From

these

two

matrices

it

is

easily

seen which combinations of exposure

time

and

development

time

produce acceptable negatives, what

the

ranges of each vari

films

the

area of acceptable negatives appears

to

lie

along

a

diagonal

with slope

approximately

equal

to

-1.

In

producing

acceptable

line

copy

reproduction

Kodak

Kodalith

Ortho

Type

3

Film

appears _superior

to

Haloid

Halolith

Film.

Conclusions

Using

just

the

measurement of gamma

by

any

of

the

three

methods and with either

film

it

is

not possible

to

predict

acceptability

of

the

product

by

the

customer.

For

Kodak

Kodalith

Ortho

Type

3

Film

the

optimum exposure

time

appears

to

be

30

seconds under

the

experimental

conditions,

with

development

varied

from

two

to

three

minutes

for

maximum

number of acceptable negatives.

For the

same

film

optimum

develop

ment

time

appears

to

be

three

minutes under experimental conditions

with exposure varied

from

12

to

30

seconds

for

maximum number of

acceptable negatives.

For

Haloid Halolith

Film

there

does

not appear

to

be

clear-cut optimum exposure and

development

times

for

maximum production

of acceptable negatives.

However,

the

area of acceptable negatives

in

the

experimental matrix appears

to

coincide quite

closely

with

the

area

for

the

Kodak

film.

The

minimum background

density

for

acceptable

line

copy

repro

duction

appears

to

be

1.8.

With

the

information obtained

in

this

experiment,

especially

that

concerning

the

background

density

of acceptable

negatives,

a

method of

measuring

gamma which would correlate with acceptable

-13

-Acknowledgments

The

author wishes

to

acknowledge

the

kind

assistance of

the

following

people:

Professor

Hollis

M.

Todd

and

Professor

Albert

D.

Rickmers,

Rochester

Institute

of

Technology;

Mr.

Robert

P.

Smith,

and

Dr.

Chung

Wei

Chen,

Xerox

Corporation;

Mr.

Warren

Rhodes,

Graphic

Arts

Research

and

Development,

Rochester

Institute

of

Technology;

Mr.

Anson

Halsey,

Mr.

C.

Peterson,

and

Mr.

John

Schoonhagen,

Case-Hoyt

Corporation;

Mr.

Fred

Hess,

Stecher-Traung

Lithographic

Corporation;

and

Mr.

E3

Potter,

Smith-Hart

Printing