ISO 8374:2001
(Main)Photography — Determination of ISO safelight conditions
Photography — Determination of ISO safelight conditions
This International Standard specifies the methods for determining the maximum exposure time that a given sensitized material can receive from a given safelight without affecting the quality of the final image. It also specifies the records which shall be maintained for the components of a safelight and its operating environment.
Photographie — Détermination des conditions d'éclairage de sécurité ISO
Fotografija - Ugotavljanje varnih svetlobnih razmer po ISO (v temnicah)
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 8374
Second edition
2001-08-15
Photography — Determination of ISO
safelight conditions
Photographie — Détermination des conditions d'éclairage de sécurité ISO
Reference number
ISO 8374:2001(E)
©
ISO 2001
---------------------- Page: 1 ----------------------
ISO 8374:2001(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2001
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 734 10 79
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 8374:2001(E)
Contents Page
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Maintenance and recording of safelight conditions .3
5 Test methods.3
5.1 Introduction.3
5.2 Method 1 .4
5.3 Method 2 .6
6 Test method for safelight conditions during processing.9
7 Evaluation.10
7.1 General.10
7.2 Subjective (visual) procedure.10
7.3 Objective (instrumental) procedure.10
8 Designation .10
Annex A (normative) Safelight testing using a half-tone image .11
Bibliography.13
© ISO 2001 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 8374:2001(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 8374 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replace the first edition (ISO 8374:1986), which has been technically revised.
Annex A forms a normative part of this International Standard.
iv © ISO 2001 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 8374:2001(E)
Introduction
The term “safelight” in photography is used to describe a light source that offers the user sufficient time to perform
an operation without producing a detectable change in the photographic characteristics of a sensitized material.
Because most sensitized materials are handled under safelight conditions by the manufacturers or users, or both, it
was considered desirable to specify a standard method to determine working conditions which are safe for
sensitized materials.
It is usually assumed, often incorrectly, that lighting conditions are safe if the density in a simple “fog test” is not
changed by these conditions. This is untrue for many materials, particularly for black-and-white and colour papers,
where an image area may be more sensitive than an unexposed area. Therefore, an unsafe lighting condition may
go undetected if one looks for changes in unexposed areas only. Furthermore, the sensitivity of a sensitized
product to a safelight may differ according to whether the safelight exposure is received before or after the practical
exposure, and the magnitude or even the direction of this difference may in some cases vary from batch to batch of
a given film or paper type.
An additional consideration is the cumulative effect of successive exposures. Depending on the types of exposures
and the emulsion formulation of the particular sensitized product, these exposures may be subadditive, additive or
superadditive.
Generally, the spectral quality for a safelight is selected as a compromise between the visual response of a partially
dark-adapted operator and the spectral response (of the product) to this light. This International Standard is not
concerned with this selection.
The object of this International Standard is to define when the exposure (the product of intensity and time) from a
safelight has a detectable effect on the image-forming characteristics of a sensitized material. Since virtually all
exposures are cumulative, exposure of a material to safelights should be kept to a minimum at all stages of
handling (i.e., manufacturing, inspection, camera loading, splicing, processing, printing, etc.).
This International Standard provides a means to isolate and evaluate any given single exposure to safelight
irradiation among the several exposures likely to be incurred in the manufacturing and use cycle.
© ISO 2001 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 8374:2001(E)
Photography — Determination of ISO safelight conditions
1 Scope
This International Standard specifies the methods for determining the maximum exposure time that a given
sensitized material can receive from a given safelight without affecting the quality of the final image. It also
specifies the records which shall be maintained for the components of a safelight and its operating environment.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 5-2:2001, Photography� Density measurements� Part 2: Geometric conditions for transmission density.
ISO 5-3:1995, Photography� Density measurements� Part 3: Spectral conditions.
ISO 5-4:1995, Photography� Density measurements� Part 4: Geometric conditions for reflection density.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
additivity
condition wherein the effect of successive exposures received by a sensitized product produces a net photographic
effect that is precisely that which would be predicted by a mathematical summation of the individual exposures
3.2
dot value
apparent percentage of an area covered by half-tone dots which is calculated from the relative transmission
densities of the area of dots, the solid area, and the area between dots
3.3
geometric mean
the nth root of the product of n quantities, referring here to the square root of the product of two adjacent safelight
exposure values
3.4
half-tone image
image composed of dots at a given screen frequency (number of dots per centimetre) that are varied in size (value)
and shape to provide visual tonal gradations
© ISO 2001 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 8374:2001(E)
3.5
hard dot
half-tone dot with a sufficiently steep edge gradient such that the dot reproduces reliably in film duplication and in
the production of a printing plate
3.6
ISO maximum safelight condition
lighting condition that provides half of that exposure which is the geometric mean between the exposure required to
produce the smallest detectable change and the (adjacent) maximum exposure which gives no detectable change,
evaluated by use of methods described in this International Standard
3.7
post-exposure
latensification
safelight exposure after a sensitized material receives a normal image-forming exposure
3.8
pre-exposure
hypersensitization
safelight exposure before a sensitized material receives a normal image-forming exposure
3.9
safelight
combination of light source, filter and fixture yielding a specific spectral irradiance, appropriate for handling a
particular sensitized material
NOTE In some cases, the source itself may be spectrally correct without the need for a filter.
3.10
safelight filter
spectrally selective absorbing material used with a specified light source to produce the required safelight
illumination
3.11
safelight fixture
enclosure for a light source (such as tungsten) that dissipates heat and holds a safelight filter (if either are required)
3.12
safelight irradiance
electromagnetic radiation emanating from a safelight that is incident on a sensitized material
NOTE A sensitized material generally has a spectral sensitivity very different from the human eye. This makes it possible
for two safelights of differing spectral-power distributions to give the same “visual appearance” but affect a sensitized material
quite differently.
3.13
safelight scale exposure
exposure series using the safelight as the light source
3.14
safetime
length of time that a sensitized product can be exposed to a safelight of a given intensity at a given distance
NOTE This will be any time less than or equal to one-half of the geometric mean between the time required to produce the
smallest detectable change and the maximum time which gives no detectable change in a sensitized product, using the test
conditions outlined in this International Standard.
2 © ISO 2001 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 8374:2001(E)
3.15
smallest detectable change
smallest difference in the image density or hue that, for a given sensitized product, can be seen in a side-by-side
visual examination
NOTE This can alternatively be measured by a densitometer if it has accuracy of density difference and repeatability better
than or equal to either 0,005 or 0,5 % of the density, whichever is the greater.
3.16
stop
term referring to a factor of two change in exposure, or a change of approximately 0,3 log exposure
10
3.17
subadditivity
condition wherein the effect of successive exposures received by a sensitized product produces a net photographic
effect that is less than that predicted by a mathematical summation of the individual exposures
3.18
superadditivity
condition wherein the effect of successive exposures received by a sensitized product produces a net photographic
effect that is more than that predicted by a mathematical summation of the individual exposures
NOTE The phenomenon of superadditivity is demonstrated by most print materials. Method 1 determines at what density a
given sensitized material is most sensitive to safelight exposure. In some cases, the material may be most sensitive over a
range of densities from fog upwards; in such cases, a simple fog test would be adequate.
4 Maintenance and recording of safelight conditions
A record shall be made of all pertinent data including the safelight source type (e.g. light-emitting diode,
electroluminescent panel, tungsten bulb, sodium vapour lamp, etc.), source wattage or milliamp draw, voltage, filter
used (if any), approximate age of the filter, type and interior finish (e.g. white, matte black, silvered, etc.) of the
safelight fixture, distance from the safelight to the sensitized material, exposure times and processing data. The
data for indirect safelight illumination (aimed at walls or ceilings) shall also include the colour and reflectance of the
surfaces and appropriate geometrical descriptions.
Once established, the safelight exposure variable shall be maintained by ensuring that proper replacement lamps
are used, that filters are not fading, that the distance from the safelight to the sensitized material is maintained, and
that the environment has not changed (by painting walls, etc.).
Any changes to the elements described above shall be evaluated individually via methods set forth in this
International Standard.
5 Test methods
5.1 Introduction
This clause describes two methods of testing to determine the maximum safelight condition.
� Method 1 (see 5.2): the most general method and the one that shall be used when the safelight/material
relationship is unknown. It makes no assumptions regarding
a) the image density at which safelight exposure produces the maximum effect, and
b) the order of exposures (safelight and image) that produces the maximum effect.
© ISO 2001 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 8374:2001(E)
� Method 2 (see 5.3): intended for use only when the basic relationship between safelight and sensitized
material is already known. It is thus useful for in situ testing of safelit areas, once Method 1 has yielded the
safelight/material relationship. (Method 1 may also be used for in situ testing, but it is more cumbersome than
Method 2.)
In Method 2, the image exposure is simulated by a uniform exposure that produces the greatest sensitivity to
subsequent safelight exposure. (In some cases, the material may be most sensitive over a range of densities from
fog upwards; here, Method 2 can be reduced to a simple fog test.) The description in 5.3 includes testing both
orders of exposures (safelight then image, and image then safelight); but if the order producing the greatest
safelight sensitivity is known, or if only one order is relevant (e.g. in an area where photographic materials are
manufactured), the other order may be omitted.
Method 2 can be accomplished using a single sheet of sensitized material, as opposed to Method 1 which requires
several sheets.
5.2 Method 1
5.2.1 Principle
Separate samples are subjected to a series of safelight exposures before the image exposure and after the image
exposure. The maximum safelight exposure which does not affect the image, and also the exposure required to
produce the smallest detectable change, are determined and used to define the “ISO maximum safelight condition”.
Alternatively, if one has already determined whether a given sensitized product shows the first detectable change
in the unexposed areas or in the exposed areas at a particular density, the safelight series may be performed on
one sample (Method 2, see 5.3).
5.2.2 Apparatus
5.2.2.1 Step tablet
The use of a transmission step tablet is recommended to create a series of stepped exposures which will provide
the range of densities expected in the normal use of the material to be evaluated. For products normally exposed
with direct X-rays, the exposure series shall be obtained in a manner appropriate for radiographic films. For
products normally exposed to a half-tone pattern, the method specified in annex A shall be initially completed in
parallel with Method 1. For subsequent testing, the method showing the most sensitivity (the half-tone method of
annex A or the continuous-tone method of the main body of this International Standard) shall be used.
If a step tablet is not available, the following procedure may be substituted for the exposure. Cover one end of the
piece of sensitized material being tested with a black card or other opaque material and uniformly flash expose the
uncovered area, moving the card to produce a series of exposure times such as 1 s, 2 s, 4 s, 8 s, 16 s, etc. The
spectral quality of the illuminant shall be similar to that normally used for the material. The exposures should
produce the full range of densities expected in actual use. A less satisfactory alternative is to give the entire piece
of sensitized material, except for a protected border, a uniform exposure through a transparent picture image,
providing the picture produces a satisfactory distribution of light, medium and dark tones.
It is important to remember that areas receiving lower image exposures are particularly vulnerable to the effects of
low-level exposures as might occur under safelight conditions.
5.2.2.2 Opaque cover
A black opaque card is needed to limit the area exposed to the safelight illumination. Additional pieces of card and
masking tape may be used in the construction of a guide for positioning the sensitized material and the opaque
card in the dark.
5.2.2.3 Timer
A means of timing the exposure from the safelight fo
...
SLOVENSKI STANDARD
SIST ISO 8374:2003
01-april-2003
Fotografija - Ugotavljanje varnih svetlobnih razmer po ISO (v temnicah)
Photography -- Determination of ISO safelight conditions
Photographie -- Détermination des conditions d'éclairage de sécurité ISO
Ta slovenski standard je istoveten z: ISO 8374:2001
ICS:
37.040.20 )RWRJUDIVNLSDSLUILOPLLQ Photographic paper, films
IRWRJUDIVNHSORãþH)LOPVNL and cartridges
]YLWNL
SIST ISO 8374:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST ISO 8374:2003
---------------------- Page: 2 ----------------------
SIST ISO 8374:2003
INTERNATIONAL ISO
STANDARD 8374
Second edition
2001-08-15
Photography — Determination of ISO
safelight conditions
Photographie — Détermination des conditions d'éclairage de sécurité ISO
Reference number
ISO 8374:2001(E)
©
ISO 2001
---------------------- Page: 3 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO 2001
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 734 10 79
E-mail copyright@iso.ch
Web www.iso.ch
Printed in Switzerland
ii © ISO 2001 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
Contents Page
1 Scope .1
2 Normative references .1
3 Terms and definitions .1
4 Maintenance and recording of safelight conditions .3
5 Test methods.3
5.1 Introduction.3
5.2 Method 1 .4
5.3 Method 2 .6
6 Test method for safelight conditions during processing.9
7 Evaluation.10
7.1 General.10
7.2 Subjective (visual) procedure.10
7.3 Objective (instrumental) procedure.10
8 Designation .10
Annex A (normative) Safelight testing using a half-tone image .11
Bibliography.13
© ISO 2001 – All rights reserved iii
---------------------- Page: 5 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 8374 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replace the first edition (ISO 8374:1986), which has been technically revised.
Annex A forms a normative part of this International Standard.
iv © ISO 2001 – All rights reserved
---------------------- Page: 6 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
Introduction
The term “safelight” in photography is used to describe a light source that offers the user sufficient time to perform
an operation without producing a detectable change in the photographic characteristics of a sensitized material.
Because most sensitized materials are handled under safelight conditions by the manufacturers or users, or both, it
was considered desirable to specify a standard method to determine working conditions which are safe for
sensitized materials.
It is usually assumed, often incorrectly, that lighting conditions are safe if the density in a simple “fog test” is not
changed by these conditions. This is untrue for many materials, particularly for black-and-white and colour papers,
where an image area may be more sensitive than an unexposed area. Therefore, an unsafe lighting condition may
go undetected if one looks for changes in unexposed areas only. Furthermore, the sensitivity of a sensitized
product to a safelight may differ according to whether the safelight exposure is received before or after the practical
exposure, and the magnitude or even the direction of this difference may in some cases vary from batch to batch of
a given film or paper type.
An additional consideration is the cumulative effect of successive exposures. Depending on the types of exposures
and the emulsion formulation of the particular sensitized product, these exposures may be subadditive, additive or
superadditive.
Generally, the spectral quality for a safelight is selected as a compromise between the visual response of a partially
dark-adapted operator and the spectral response (of the product) to this light. This International Standard is not
concerned with this selection.
The object of this International Standard is to define when the exposure (the product of intensity and time) from a
safelight has a detectable effect on the image-forming characteristics of a sensitized material. Since virtually all
exposures are cumulative, exposure of a material to safelights should be kept to a minimum at all stages of
handling (i.e., manufacturing, inspection, camera loading, splicing, processing, printing, etc.).
This International Standard provides a means to isolate and evaluate any given single exposure to safelight
irradiation among the several exposures likely to be incurred in the manufacturing and use cycle.
© ISO 2001 – All rights reserved v
---------------------- Page: 7 ----------------------
SIST ISO 8374:2003
---------------------- Page: 8 ----------------------
SIST ISO 8374:2003
INTERNATIONAL STANDARD ISO 8374:2001(E)
Photography — Determination of ISO safelight conditions
1 Scope
This International Standard specifies the methods for determining the maximum exposure time that a given
sensitized material can receive from a given safelight without affecting the quality of the final image. It also
specifies the records which shall be maintained for the components of a safelight and its operating environment.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 5-2:2001, Photography� Density measurements� Part 2: Geometric conditions for transmission density.
ISO 5-3:1995, Photography� Density measurements� Part 3: Spectral conditions.
ISO 5-4:1995, Photography� Density measurements� Part 4: Geometric conditions for reflection density.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
additivity
condition wherein the effect of successive exposures received by a sensitized product produces a net photographic
effect that is precisely that which would be predicted by a mathematical summation of the individual exposures
3.2
dot value
apparent percentage of an area covered by half-tone dots which is calculated from the relative transmission
densities of the area of dots, the solid area, and the area between dots
3.3
geometric mean
the nth root of the product of n quantities, referring here to the square root of the product of two adjacent safelight
exposure values
3.4
half-tone image
image composed of dots at a given screen frequency (number of dots per centimetre) that are varied in size (value)
and shape to provide visual tonal gradations
© ISO 2001 – All rights reserved 1
---------------------- Page: 9 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
3.5
hard dot
half-tone dot with a sufficiently steep edge gradient such that the dot reproduces reliably in film duplication and in
the production of a printing plate
3.6
ISO maximum safelight condition
lighting condition that provides half of that exposure which is the geometric mean between the exposure required to
produce the smallest detectable change and the (adjacent) maximum exposure which gives no detectable change,
evaluated by use of methods described in this International Standard
3.7
post-exposure
latensification
safelight exposure after a sensitized material receives a normal image-forming exposure
3.8
pre-exposure
hypersensitization
safelight exposure before a sensitized material receives a normal image-forming exposure
3.9
safelight
combination of light source, filter and fixture yielding a specific spectral irradiance, appropriate for handling a
particular sensitized material
NOTE In some cases, the source itself may be spectrally correct without the need for a filter.
3.10
safelight filter
spectrally selective absorbing material used with a specified light source to produce the required safelight
illumination
3.11
safelight fixture
enclosure for a light source (such as tungsten) that dissipates heat and holds a safelight filter (if either are required)
3.12
safelight irradiance
electromagnetic radiation emanating from a safelight that is incident on a sensitized material
NOTE A sensitized material generally has a spectral sensitivity very different from the human eye. This makes it possible
for two safelights of differing spectral-power distributions to give the same “visual appearance” but affect a sensitized material
quite differently.
3.13
safelight scale exposure
exposure series using the safelight as the light source
3.14
safetime
length of time that a sensitized product can be exposed to a safelight of a given intensity at a given distance
NOTE This will be any time less than or equal to one-half of the geometric mean between the time required to produce the
smallest detectable change and the maximum time which gives no detectable change in a sensitized product, using the test
conditions outlined in this International Standard.
2 © ISO 2001 – All rights reserved
---------------------- Page: 10 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
3.15
smallest detectable change
smallest difference in the image density or hue that, for a given sensitized product, can be seen in a side-by-side
visual examination
NOTE This can alternatively be measured by a densitometer if it has accuracy of density difference and repeatability better
than or equal to either 0,005 or 0,5 % of the density, whichever is the greater.
3.16
stop
term referring to a factor of two change in exposure, or a change of approximately 0,3 log exposure
10
3.17
subadditivity
condition wherein the effect of successive exposures received by a sensitized product produces a net photographic
effect that is less than that predicted by a mathematical summation of the individual exposures
3.18
superadditivity
condition wherein the effect of successive exposures received by a sensitized product produces a net photographic
effect that is more than that predicted by a mathematical summation of the individual exposures
NOTE The phenomenon of superadditivity is demonstrated by most print materials. Method 1 determines at what density a
given sensitized material is most sensitive to safelight exposure. In some cases, the material may be most sensitive over a
range of densities from fog upwards; in such cases, a simple fog test would be adequate.
4 Maintenance and recording of safelight conditions
A record shall be made of all pertinent data including the safelight source type (e.g. light-emitting diode,
electroluminescent panel, tungsten bulb, sodium vapour lamp, etc.), source wattage or milliamp draw, voltage, filter
used (if any), approximate age of the filter, type and interior finish (e.g. white, matte black, silvered, etc.) of the
safelight fixture, distance from the safelight to the sensitized material, exposure times and processing data. The
data for indirect safelight illumination (aimed at walls or ceilings) shall also include the colour and reflectance of the
surfaces and appropriate geometrical descriptions.
Once established, the safelight exposure variable shall be maintained by ensuring that proper replacement lamps
are used, that filters are not fading, that the distance from the safelight to the sensitized material is maintained, and
that the environment has not changed (by painting walls, etc.).
Any changes to the elements described above shall be evaluated individually via methods set forth in this
International Standard.
5 Test methods
5.1 Introduction
This clause describes two methods of testing to determine the maximum safelight condition.
� Method 1 (see 5.2): the most general method and the one that shall be used when the safelight/material
relationship is unknown. It makes no assumptions regarding
a) the image density at which safelight exposure produces the maximum effect, and
b) the order of exposures (safelight and image) that produces the maximum effect.
© ISO 2001 – All rights reserved 3
---------------------- Page: 11 ----------------------
SIST ISO 8374:2003
ISO 8374:2001(E)
� Method 2 (see 5.3): intended for use only when the basic relationship between safelight and sensitized
material is already known. It is thus useful for in situ testing of safelit areas, once Method 1 has yielded the
safelight/material relationship. (Method 1 may also be used for in situ testing, but it is more cumbersome than
Method 2.)
In Method 2, the image exposure is simulated by a uniform exposure that produces the greatest sensitivity to
subsequent safelight exposure. (In some cases, the material may be most sensitive over a range of densities from
fog upwards; here, Method 2 can be reduced to a simple fog test.) The description in 5.3 includes testing both
orders of exposures (safelight then image, and image then safelight); but if the order producing the greatest
safelight sensitivity is known, or if only one order is relevant (e.g. in an area where photographic materials are
manufactured), the other order may be omitted.
Method 2 can be accomplished using a single sheet of sensitized material, as opposed to Method 1 which requires
several sheets.
5.2 Method 1
5.2.1 Principle
Separate samples are subjected to a series of safelight exposures before the image exposure and after the image
exposure. The maximum safelight exposure which does not affect the image, and also the exposure required to
produce the smallest detectable change, are determined and used to define the “ISO maximum safelight condition”.
Alternatively, if one has already determined whether a given sensitized product shows the first detectable change
in the unexposed areas or in the exposed areas at a particular density, the safelight series may be performed on
one sample (Method 2, see 5.3).
5.2.2 Apparatus
5.2.2.1 Step tablet
The use of a transmission step tablet is recommended to create a series of stepped exposures which will provide
the range of densities expected in the normal use of the material to be evaluated. For products normally exposed
with direct X-rays, the exposure series shall be obtained in a manner appropriate for radiographic films. For
products normally exposed to a half-tone pattern, the method specified in annex A shall be initially completed in
parallel with Method 1. For subsequent testing, the method showing the most sensitivity (the half-tone method of
annex A or the continuous-tone method of the main body of this International Standard) shall be used.
If a step tablet is not available, the following procedure may be substituted for the exposure. Cover one end of the
piece of sensitized material being tested with a black card or other opaque material and uniformly flash expose the
uncovered area, moving the card to produce a series of exposure times such as 1 s, 2 s, 4 s, 8 s, 16 s, etc. The
spectral quality of the illuminant shall be similar to that normally used for the material. The exposures should
produce the full range of densities expected in actual use. A less satisfactory alternative is to give the entire piece
of sensitized material, except for a protected border, a uniform exposure through a transparent picture image,
providing the picture produces a satisfactory distribution of light, medium and dark tones.
It is important to remember that areas receiving lower
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