ASTM E1815-96
(Test Method)Standard Test Method for Classification of Film Systems for Industrial Radiography
Standard Test Method for Classification of Film Systems for Industrial Radiography
SCOPE
1.1 This test method covers a procedure for determination of the performance of film systems used for industrial radiography. This test method establishes minimum requirements that correspond to system classes.
1.2 This test method is to be used only for direct exposure-type film exposed with lead intensifying screens. The performance of films exposed with fluorescent (light-emitting) intensifying screens cannot be determined accurately by this test method.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E 1815 – 96
Standard Test Method for
Classification of Film Systems for Industrial Radiography
This standard is issued under the fixed designation E 1815; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope metric Conditions for Transmission Density
ISO 5-3 Photography Density Measurements—Part 3:
1.1 This test method covers a procedure for determination
Spectral Conditions
of the performance of film systems used for industrial radiog-
ISO 7004 Photography—Industrial Radiographic Film, De-
raphy. This test method establishes minimum requirements that
termination of ISO Speed and Average Gradient When
correspond to system classes.
Exposed to X and Gamma Radiation
1.2 This test method is to be used only for direct exposure-
type film exposed with lead intensifying screens. The perfor-
3. Terminology
mance of films exposed with fluorescent (light-emitting) inten-
3.1 Definitions—For definitions of terms used in this test
sifying screens cannot be determined accurately by this test
method, refer to Terminology E 1316.
method.
3.2 Definitions of Terms Specific to This Standard:
1.3 The values stated in SI units are to be regarded as the
3.2.1 film system—the film and associated film-processing
standard. The values given in parentheses are for information
requirements according to the criteria established by the
only.
manufacturers of the film and processing chemicals.
1.4 This standard does not purport to address all of the
3.2.2 gradient G—the slope of the characteristic curve at a
safety concerns, if any, associated with its use. It is the
certain density, D, and a measure of the contrast of the film
responsibility of the user of this standard to establish appro-
system.
priate safety and health practices and determine the applica-
3.2.3 granularity, s —the stochastic density fluctuations in
D
bility of regulatory limitations prior to use.
the radiograph that are superimposed to the object image.
2. Referenced Documents 3.2.4 ISO speed S—determined by the dose K , measured in
s
gray at a specified optical density, D, in the radiograph.
2.1 ASTM Standards:
E 94 Guide for Radiographic Testing
4. Significance and Use
E 999 Guide for Controlling the Quality of Industrial Ra-
2 4.1 This test method provides a relative means for classifi-
diographic Film Processing
cation of film systems used for industrial radiography. The film
E 1079 Practice for Calibration of Transmission Densitom-
2 system consists of the film and associated processing system
eters
(the type of processing and processing chemistry). Section 6
E 1316 Terminology for Nondestructive Examinations
3 describes specific parameters used for this test method. In
2.2 ANSI Standards:
general, the classification for hard X rays, as described in
PH 2.18 Photography (Sensitometry)—Density Measure-
Section 6, can be transferred to other radiation energies and
ments, Spectral Conditions
metallic screen types, as well as screens without films. The
PH 2.19 Photography Density Measurements—Part 2: Geo-
usage of film system parameters outside the energy ranges
metric Conditions for Transmission Density
specified may result in changes to a film/system performance
PH 2.40 Root Mean Square (rms) Granularity of Film
classification.
(Images on One Side Only) Method of Measuring
3 4.1.1 The film performance is described by signal and noise
2.3 ISO Standards:
parameters. The signal is represented by gradient and the noise
ISO 5-2 Photography Density Measurements—Part 2: Geo-
by granularity.
4.1.2 A film is assigned a particular class if it meets all four
of the minimum performance parameters: for Gradient G at D
This test method is under the jurisdiction of ASTM Committee E-7 on
Nondestructive Testing and is the direct responsibility of Subcommittee E07.01 on
5 2.0 and D 5 4.0, granularity s at D 5 2.0, and gradient/
D
Radiology (X and Gamma) Method.
noise ratio at D 5 2.0.
Current edition approved May 10, 1996. Published July 1996.
2 4.2 This test method describes how the parameters shall be
Annual Book of ASTM Standards, Vol 03.03.
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
E 1815
measured and demonstrates how a classification table can be 6.2 X-ray Spectral Quality:
constructed. 6.2.1 Use the same X-ray spectral quality for determining
4.3 Manufacturers of industrial radiographic film systems
both the film gradient and its root mean square granularity.
will be the users of this test method. The result is a classifica- Make the film exposures with an 8-mm (0.32-in.) copper filter
tion table as shown by the example given in Table 1. This table
at the X-ray tube and the kilovoltage set such that the half value
also includes speed data for user information. Users of indus- layer in copper is 3.5 mm (0.14 in.). The kilovoltage setting
trial radiographic film systems may also perform the tests and
will be approximately 220 kV.
measurements outlined in this test method, provided that the 6.2.2 Determine the required kilovoltage setting by making
required test equipment is used and the methodology is
an exposure (or exposure rate) measurement with the detector
followed strictly. placed at a distance of at least 750 mm (29.5 in.) from the tube
4.4 The publication of classes for industrial radiography
target and an 8-mm (0.32-in.) copper filter at the tube. Then
film systems will enable specifying bodies and contracting make a second measurement with a total of 11.5 mm (0.45 in.)
parties to agree to particular system classes, which are capable
of copper at the tube. These filters should be made of 99.9 %
of providing known image qualities. See 7.2. pure copper.
6.2.3 Calculate the ratio of the first and second readings. If
5. Sampling and Storage
this ratio is not 2, adjust the kilovoltage up or down and repeat
5.1 For determination of the gradient and granularity of a
the measurements until a ratio of 2 (within 5 %) is obtained.
film system, it is important that the samples evaluated yield the Record the machine setting of the kilovoltage for use with the
average results obtained by users. This will require evaluating
film tests.
several different batches periodically, under the conditions
6.3 Film Cassette and Screens:
specified in this test method. Prior to evaluation, the samples
6.3.1 The film cassette (holder) shall provide a means of
shall be stored according to the manufacturer’s recommenda-
ensuring good film screen contact. A vacuum cassette may be
tions for a length of time to simulate the average age at which
used.
the product is normally used. Several independent evaluations
6.3.2 Lead-foil screens shall be used with the front screen
shall be made to ensure the proper calibration of equipment and
thickness being 0.130 6 0.013 mm (0.005 6 0.05 in.) and the
processes. The basic objective in selecting and storing samples
back screen thickness being 0.250 6 0.025 mm (0.010 6 0.001
as described above is to ensure that the film characteristics are
in.).
representative of those obtained by a consumer at the time of
NOTE 1—These thicknesses reflect commercially available tolerances
use.
in lead foil for use as radiographic screens.
6. Procedure
6.3.3 It is especially important that the exposure to the film
6.1 Principle: specimen for the granularity measurements be spatially uni-
form. Any nonuniformities in X-ray transmission of the cas-
6.1.1 Film to be tested shall be exposed to X rays from
tungsten target tubes. Inherent filtration of the tube, plus an sette front or nonuniformities or defects in the lead-foil screens
could influence the granularity measurement. Therefore, exer-
additional copper filter located as close to the target as possible,
cise considerable care in selection and maintenance of the
shall provide filtration equivalent to 8.00 6 0.2 mm of copper.
cassette and lead screens to minimize these effects.
6.1.2 The film system includes a front and a back screen of
0.02 to 0.25-mm lead. If single-coated films are used, the 6.3.4 Expose single-coated films with the emulsion-coated
surface in contact with the front screen.
emulsion-coated surface must face the X-ray tube. Vacuum or
pressure cassettes may be used to ensure sufficient contact 6.4 Film Processing—The film image quality will vary with
between the film and screen. the processing variables, such as chemistry, temperature, and
TABLE 1 Typical Film System Classification
Automatic Film Processing
Developer: Type A
Developer immersion time: XXX seconds
Developer temperature: XX°C/YY°F
Minimum
Minimum Gradient G at
Gradient/ Maximum
ASTM System Granularity Granularity, s , ISO Speed Dose, K ,m Gy,
A D s
Film Type
Class Ratio, G/s ,at at D 5 2.0 above S D 5 2.0
D
D 5 2.0 D 5 4.0
D 5 2.0 above D
o
above D above D
o o
D
o
A Special 5.4 9.1 360 0.015 32 29.0
B I 4.5 8.4 281 0.016 64 14.0
C I 4.4 7.6 232 0.019 100 8.7
D I 4.4 7.6 169 0.026 200 4.6
E II 4.4 7.6 142 0.031 320 3.2
F III 4.0 5.2 114 0.035 400 2.5
G W-A 4.2 6.5 225 0.019 100 8.6
H W-B 4.1 5.3 170 0.025 300 5.0
A
Family of films ranging in speed and image quality.
E 1815
method of processing (manual or automatic). The film process- by transmitted light. The film may have emulsion coated on
ing and record requirements shall be in accordance with Guide one side or both sides of the film support.
E 999.
6.7.3 Expose the film specimen with X rays having the
6.5 Exposure Conditions:
spectral quality described in 6.2. The cassette and lead-foil
6.5.1 The plane of the film shall be normal to the central ray
screens shall be as specified in 6.3. Expose the film specimen
of the X-ray beam. Use a diaphragm at the tube to limit the
in accordance with the exposure conditions of 6.5. Exercise
field of radiation to the film area. The X-ray tube target to film
care to ensure that the film specimen does not contain density
distance shall be adequate to ensure that the exposure over the
variations arising from the exposing equipment (such as
useful area of each exposure step is uniform to within 3 %.
nonuniform beam filters or damaged or defective lead screens).
6.5.2 To minimize the effects of backscattered radiation, use
During and after exposure, prior to processing, maintain the
1 1
a 6.3 6 0.8-mm ( ⁄4 6 ⁄32-in.) thick lead shielding behind the
film specimen at the temperature and relative humidity condi-
cassette. The shielding lead shall extend at least 25 mm (1 in.)
tions specified in 6.5.5. The film processing chemicals and
beyond each edge of the cassette. Alternatively, the shielding
procedures shall be the same as those used for determining
lead may be omitted, provided that the cassette is supported
gradient, and they shall be described completely as specified in
such that the X-ray beam strikes no scattering material, other
6.4.
than air, for a distance of at least 2 m (78.7 in.) behind the
6.7.4 The film specimen for granularity measurement shall
cassette.
have a diffuse density of 2.00 6 0.05 above base plus fog. As
6.5.3 Modulation of the X-ray exposure may be accom-
an alternative, three or more samples of the film specimen at
plished by changing the exposure time or tube target to film
different density levels, within the range from 1.80 to 2.20,
distance. Changing the tube current is not recommended but
may be measured, and the granularity value at a diffuse density
may be done, provided it is verified by measurement (see 6.2)
of 2.00, above base plus fog, shall be taken from a smooth
that the X-ray spectral quality does not change.
curve drawn through a plot of the data points. The granularity
6.5.4 Measure exposures with an air-ionization chamber, or
value shall be in terms of diffuse density.
other types of X-ray detectors, having linear response over the
6.7.4.1 The microdensitometer scanner output is measured
range of X-ray intensities and exposure times used for the film
as projection density. Thus to obtain the desired diffuse density,
exposures.
convert the data using the slope of the curve of diffuse density
6.5.5 During and after exposure, prior to processing, keep
versus projection density at the mean density value of the
the film at a temperature of 23 6 5°C (59.7 6 5°F) and a
granularity film specimen. Determine this curve using a film
relative humidity of 50 6 20 %. Start processing of the film
having a stepped series of densities, which is prepared using
between 30 min and 8 h after exposure. Process an unexposed
the same type film, exposure, and processing techniques as
specimen of the film sample with the X-ray-exposed specimen
used for the granularity film specimen. Measure the diffuse
in order to determine the base plus fog density.
density of each step with a microdensitometer. The specimen
6.5.6 Measure the visual diffuse transmission density of the
film shall be scanned using identical microdensitometer set-
processed films with a densitometer complying with the
tings. A limited range of densities can typically be measured
requirements of ANSI PH 2.19 and ISO 5-2 and calibrated by
for a given microdensitometer gain setting. The stepped series
the method of Practice E 1079. Use a minimum aperture of 7
of densities shall lie within that range. Choose the number of
mm (0.275 in.).
steps such that the slope of the curve, at the mean density of the
6.6 Measurement of Gradient G:
granularity film specimen, is determined to an accuracy of 6
6.6.1 Gradient G relates to a D versus log K curve. In the
5%.
scope of this test method, G is calculated from the slope of a D
6.7.5 Determine the granularity of the film specimen by
versus K curve at density (D−D ), as follows:
o
evaluating no fewer than three samples of the specimen and
dD K dD determining their mean so that a maximal uncertainty of 10 %
G 5 5 3 (1)
d log K log e dK
is achieved.
6.7.6 Adjust the optical system of the microdensitometer so
where:
that both emulsions, or the one emulsion in the case of a
K 5 dose required for density D − D , and
o
single-coated film, are in focus at all points in the scan.
D 5 fog and base density.
o
6.7.7 Scan the film specimen along three different paths
6.6.2 The D versus K curve is approximated by a polyno-
within the test area. Take the median of the three granularity
mial of the third order. To obtain a regular and reliable shape
readings as the granularity of the film specimen at the mean
of this curve, make a series of exposures to obtain at least 12
measured density.
uniformly distributed measuring points between density 1.0
6.7
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