ASTM E1815-96(2001)
(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 (Reapproved 2001)
Standard Test Method for
Classification of Film Systems for Industrial Radiography
This standard is issued under the fixed designation E1815; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope ISO 5-2 Photography Density Measurements—Part 2: Geo-
metric Conditions for Transmission Density
1.1 This test method covers a procedure for determination
ISO 5-3 Photography Density Measurements—Part 3:
of the performance of film systems used for industrial radiog-
Spectral Conditions
raphy.Thistestmethodestablishesminimumrequirementsthat
ISO 7004 Photography—Industrial Radiographic Film, De-
correspond to system classes.
termination of ISO Speed and Average Gradient When
1.2 This test method is to be used only for direct exposure-
Exposed to X and Gamma Radiation
type film exposed with lead intensifying screens. The perfor-
mance of films exposed with fluorescent (light-emitting) inten-
3. Terminology
sifying screens cannot be determined accurately by this test
3.1 Definitions—For definitions of terms used in this test
method.
method, refer to Terminology E1316.
1.3 The values stated in SI units are to be regarded as the
3.2 Definitions of Terms Specific to This Standard:
standard. The values given in parentheses are for information
3.2.1 film system—the film and associated film-processing
only.
requirements according to the criteria established by the
1.4 This standard does not purport to address all of the
manufacturers of the film and processing chemicals.
safety concerns, if any, associated with its use. It is the
3.2.2 gradient G—the slope of the characteristic curve at a
responsibility of the user of this standard to establish appro-
certain density, D, and a measure of the contrast of the film
priate safety and health practices and determine the applica-
system.
bility of regulatory limitations prior to use.
3.2.3 granularity, s —the stochastic density fluctuations in
D
2. Referenced Documents the radiograph that are superimposed to the object image.
3.2.4 ISO speed S—determinedbythedose K ,measuredin
s
2.1 ASTM Standards:
2 gray at a specified optical density, D, in the radiograph.
E94 Guide for Radiographic Examination
E999 Guide for Controlling the Quality of Industrial Ra-
4. Significance and Use
diographic Film Processing
4.1 This test method provides a relative means for classifi-
E1079 Practice for Calibration of Transmission Densitom-
2 cationoffilmsystemsusedforindustrialradiography.Thefilm
eters
2 system consists of the film and associated processing system
E1316 Terminology for Nondestructive Examinations
3 (the type of processing and processing chemistry). Section 6
2.2 ANSI Standards:
describes specific parameters used for this test method. In
PH 2.18 Photography (Sensitometry)—Density Measure-
general, the classification for hard X rays, as described in
ments, Spectral Conditions
Section 6, can be transferred to other radiation energies and
PH2.19 PhotographyDensityMeasurements—Part2:Geo-
metallic screen types, as well as screens without films. The
metric Conditions for Transmission Density
usage of film system parameters outside the energy ranges
PH 2.40 Root Mean Square (rms) Granularity of Film
specified may result in changes to a film/system performance
(Images on One Side Only) Method of Measuring
3 classification.
2.3 ISO Standards:
4.1.1 The film performance is described by signal and noise
parameters.Thesignalisrepresentedbygradientandthenoise
This test method is under the jurisdiction of ASTM Committee E07 on by granularity.
Nondestructive Testing and is the direct responsibility of Subcommittee E07.01 on
4.1.2 Afilm is assigned a particular class if it meets all four
Radiology (X and Gamma) Method.
of the minimum performance parameters: for Gradient G at D
Current edition approved May 10, 1996. Published July 1996.
=2.0 and D =4.0, granularity s at D=2.0, and gradient/
Annual Book of ASTM Standards, Vol 03.03. D
Available from American National Standards Institute, 11 W. 42nd St., 13th noise ratio at D=2.0.
Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1815 – 96 (2001)
4.2 This test method describes how the parameters shall be pressure cassettes may be used to ensure sufficient contact
measured and demonstrates how a classification table can be between the film and screen.
constructed. 6.2 X-ray Spectral Quality:
4.3 Manufacturers of industrial radiographic film systems 6.2.1 Use the same X-ray spectral quality for determining
will be the users of this test method. The result is a classifica- both the film gradient and its root mean square granularity.
tiontableasshownbytheexamplegiveninTable1.Thistable Make the film exposures with an 8-mm (0.32-in.) copper filter
also includes speed data for user information. Users of indus- at the X-ray tube and the kilovoltage set such that the
trial radiographic film systems may also perform the tests and half-valuelayerincopperis3.5mm(0.14in.).Thekilovoltage
measurements outlined in this test method, provided that the setting will be approximately 220 kV.
required test equipment is used and the methodology is 6.2.2 Determine the required kilovoltage setting by making
followed strictly. an exposure (or exposure rate) measurement with the detector
4.4 The publication of classes for industrial radiography placed at a distance of at least 750 mm (29.5 in.) from the tube
film systems will enable specifying bodies and contracting target and with an 8-mm (0.32-in.) copper filter at the tube.
parties to agree to particular system classes, which are capable Then make a second measurement with a total of 11.5 mm
of providing known image qualities. See 7.2. (0.45in.)ofcopperatthetube.Thesefiltersshouldbemadeof
99.9% pure copper.
5. Sampling and Storage
6.2.3 Calculate the ratio of the first and second readings. If
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.
filmsystem,itisimportantthatthesamplesevaluatedyieldthe
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
shallbemadetoensurethepropercalibrationofequipmentand
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
as described above is to ensure that the film characteristics are
0.001 in.).
representative of those obtained by a consumer at the time of
use.
NOTE 1—These thicknesses reflect commercially available tolerances
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-
6.1.1 Film to be tested shall be exposed to X rays from form. Any nonuniformities in X-ray transmission of the cas-
tungsten target tubes. Inherent filtration of the tube, plus an settefrontornonuniformitiesordefectsinthelead-foilscreens
additionalcopperfilterlocatedasclosetothetargetaspossible, could influence the granularity measurement. Therefore, exer-
shall provide filtration equivalent to 8.00 6 0.2 mm of copper. cise considerable care in selection and maintenance of the
6.1.2 The film system includes a front and a back screen of cassette and lead screens to minimize these effects.
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
emulsion-coated surface must face the X-ray tube. Vacuum or surface in contact with the front screen.
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 = 2.0 above S D =2.0
D
D =2.0 D =4.0
D = 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 – 96 (2001)
6.4 FilmProcessing—Thefilmimagequalitywillvarywith 6.7.2 The procedure is limited to the measurement of
the processing variables, such as chemistry, temperature, and continuous tone black-and-white industrial X-ray films viewed
methodofprocessing(manualorautomatic).Thefilmprocess- 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.
E999.
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 Theplaneofthefilmshallbenormaltothecentralray
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%.
nonuniformbeamfiltersordamagedordefectiveleadscreens).
6.5.2 Tominimizetheeffectsofbackscatteredradiation,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,andtheyshallbedescribedcompletelyasspecifiedin
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
maybemeasured,andthegranularityvalueatadiffusedensity
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
asprojectiondensity.Thustoobtainthedesireddiffusedensity,
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 ofANSI PH 2.19 and ISO 5-2 and calibrated by
for a given microdensitometer gain setting. The stepped series
the method of Practice E1079. Use a minimum aperture of 7
of densities shall lie within that range. Choose the number of
mm (0.275 in.).
stepssuchthattheslopeofthecurve,atthemeandensityofthe
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%.
scopeofthistestmethod,GiscalculatedfromtheslopeofaD
versus K curve at density (D−D ), as follows: 6.7.5 Determine the granularity of the film specimen by
o
evaluating no fewer than three samples of the specimen and
dD K dD
G 5 5 3 (1)
determining their mean so that a maximal uncertainty of 10%
dlogK loge dK
is achieved.
where:
6.7.6 Adjust the optical system of the microdensitometer so
K = dose required for density D−D , and
o
that both emulsions, or the one emulsion in the case of a
D = fog and base density.
o
single-coated film, are in focus at all points in the scan.
6.6.2 The D versus K curve is approximated by a polyno-
6.7.7 Scan the film specimen along three different paths
mial of the third order. To obtain a regular and reliable shape
within the test area. Take the median of the three granularity
of this curve, make a series of exposures to obtain at least 12
readings as the granularity of the film specimen at the mean
uniformly distributed measuring points between density 1.0
measured density.
and 5.0 above D .
o
6.7.8 Microdensitometer Requiremen
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