SIST ISO 5-2:2002

SLOVENSKI STANDARD
SIST ISO 5-2:2002
01-november-2002
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SIST ISO 5-2:1996
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Photography -- Density measurements -- Part 2: Geometric conditions for transmission
density
Photographie -- Mesurage des densités -- Partie 2: Conditions géométriques pour la
densité instrumentale par transmission
Ta slovenski standard je istoveten z: ISO 5-2:2001
ICS:
37.040.01 Fotografija na splošno Photography in general
SIST ISO 5-2:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST ISO 5-2:2002

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SIST ISO 5-2:2002
INTERNATIONAL ISO
STANDARD 5-2
Fourth edition
2001-06-15
Photography — Density measurements —
Part 2:
Geometric conditions for transmission
density
Photographie — Mesurage des densités —
Partie 2: Conditions géométriques pour la densité instrumentale par
transmission
Reference number
ISO 5-2:2001(E)
©
ISO 2001

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SIST ISO 5-2:2002
ISO 5-2:2001(E)
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ii © ISO 2001 – All rights reserved

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SIST ISO 5-2:2002
ISO 5-2:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Coordinate system, terminology and symbols.2
5 ISO standard diffuse density.2
6 ISO standard projection density .5
Annex A (normative) Diffusion coefficient .7
Annex B (informative) Unmatched influx and efflux angles .10
Annex C (informative) Position of the diaphragm determining the sampling aperture .11
Bibliography.13
© ISO 2001 – All rights reserved iii

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SIST ISO 5-2:2002
ISO 5-2:2001(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 part of ISO 5 may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 5-2 was prepared by Technical Committee ISO/TC 42, Photography.
This fourth edition cancels and replaces the third edition (ISO 5-2:1991), which has been technically revised.
The changes from the third edition are as follows.
a) The diffusion coefficient describing the diffusivity of the irradiating or the detecting system has been redefined.
The definition in the third edition was inappropriate and did not describe the practice. In particular, the
determination of the diffusion coefficient now takes into account that the distribution of the radiation of the
radiating source or the sensitivity of the detector is three-dimensional.
b) A new value, needed for the diffusion coefficient, is specified. The tolerances allowed have been tightened.
c) The position of the diaphragm, which determines the sampling aperture, in relation to the front or back side of
the diffuse irradiating or receiving opal glass has been defined, since neither the opal glass nor the sample are
infinitely thin but have a finite thickness.
ISO 5 consists of the following parts, under the general title Photography — Density measurements:
� Part 1: Terms, symbols and notations
� Part 2: Geometric conditions for transmission density
� Part 3: Spectral conditions
� Part 4: Geometric conditions for reflection density
Annex A forms a normative part of this part of ISO 5. Annexes B, C and D are for information only.
iv © ISO 2001 – All rights reserved

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SIST ISO 5-2:2002
ISO 5-2:2001(E)
Introduction
This part of ISO 5 is one of a series which specifies the geometric conditions for transmission densitometry,
primarily but not exclusively, as practised in black-and-white and colour photography. The primary change from the
first edition (1974) to the second edition (1985) was the replacement of the integrating sphere method with the
“opal glass” method as the basis for specifying ISO standard diffuse transmission density. Although any means of
diffusion which meets the specifications of this part of ISO 5 may be used, the method is often denoted simply by
the words “opal glass” to differentiate it from the integrating sphere method. Slightly smaller density values are
generally obtained compared to those based on the integrating sphere method because of inter-reflections
between the opal glass and the specimen. The effect is dependent on the reflectance characteristics of the opal
glass and the surface of the specimen facing the diffuser.
The “philosophy” of this part of ISO 5 is to specify geometrical conditions for the measurement of optical densities
which are close to those used in practice. Diffuse transmission densities are, among other things, relevant for
contact printing and rating films on viewing boxes. Viewing films on light boxes is one of the most important
applications where diffuse transmission densities are relevant. Therefore, the specified conditions for the
measurement of diffuse transmission densities consider the properties of viewing boxes concerning diffusivity and
spectral reflectance factor.
This part of ISO 5 also describes the geometric conditions for two types of projection density. The spectral
conditions described are specified in ISO 5-3.
Diffuse transmission density is a measure of the modulation of light by a film that is diffusely irradiated on one side
and viewed from the other, as when a film is viewed on a diffuse transparency radiation source (illuminator). The
geometric conditions of projection with diffuse irradiation are nearly equivalent to the conditions of viewing a film on
a diffuse illuminator, the projection lens taking the place of the eye. When film is on a diffuse radiation source
(illuminator) or in contact with a print material, light is inter-reflected between the film and the nearby surface. This
inter-reflection affects the density and is best taken into account in a measuring instrument by the use of an opal
glass diffuser or integrator, rather than an integrating sphere. Apart from this fundamental reason for using
densitometers employing opal glass diffusers, such instruments are preferred because they are more durable and
more convenient to manufacture and use.
Projection density is a measure of the modulation of light by a film that is specularly irradiated on one side and is
projected by way of a specular collection system. Equipment employing optical condensers is used to view
microfilm, motion pictures, and slides, and to make projection prints. The conditions defined in this part of ISO 5 for
projection density simulate the geometric conditions affecting the transmitting characteristics of a small area on a
negative or transparency at the centre of the frame of a typical projection system employing condensers. The area
under consideration may be defined by a small opening, known as the sampling aperture, in an otherwise opaque
sheet in the frame.
The ratio of the total flux transmitted by a specimen to the total flux incident on the sampling aperture is defined as
transmittance and is of little practical use. However, the flux transmitted by the sampled area and collected by the
projection lens to form the projected image is of interest. The ratio of this flux to the flux collected when there is no
film in the sampling aperture is designated as transmittance factor, and is used as a basis for calculating projection
density.
The measured density depends on the half-angle of the cone of incident rays and the half-angle subtended by the
projection lens at the sampling aperture. These half-angles may be indicated either in degrees or by f-numbers.
Since the f-number is usually marked on projection lenses, the two types of projection density specified in this part
of ISO 5 are identified by f-numbers, namely f/4,5 and f/1,6. The f/4,5 type is frequently used since it is
representative of microfilm readers. The f/1,6 type is considered representative of motion-picture projectors.
© ISO 2001 – All rights reserved v

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SIST ISO 5-2:2002

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SIST ISO 5-2:2002
INTERNATIONAL STANDARD ISO 5-2:2001(E)
Photography — Density measurements —
Part 2:
Geometric conditions for transmission density
1 Scope
This part of ISO 5 specifies the geometric conditions for measuring ISO diffuse and f/4,5 and f/1,6 projection
transmission densities.
Diffuse density is primarily applicable to measurements of photographic images to be viewed on a transparency
illuminator (viewing box), to be contact printed, or to be projected with a system employing diffuse irradiation.
Projection density is primarily applicable to measurements of photographic images to be projected with systems
employing optical condensers.
Although primarily intended for the measurement of photographic images, the densitometric methods specified in
this part of ISO 5 are often applied to optical filters and other transparent materials.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 5. For dated references, subsequent amendments to, or revisions of, any of these publications do
not apply. However, parties to agreements based on this part of ISO 5 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 5-1:1984, Photography — Density measurements — Part 1: Terms, symbols and notations.
ISO 5-3:1995, Photography — Density measurements — Part 3: Spectral conditions.
1)
ISO 7724-1:— , Paints and varnishes — Colorimetry — Part 1: Principles.
1) To be published. (Revision of ISO 7724-1:1984)
© ISO 2001 – All rights reserved 1

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SIST ISO 5-2:2002
ISO 5-2:2001(E)
3 Terms and definitions
For the purposes of this part of ISO 5, the terms and definitions given in ISO 5-1 and the following definitions apply.
3.1
transmittance factor
T
ratio of the measured flux transmitted by a specimen to the measured flux when the specimen is removed from the
sampling aperture of the measuring device
�
�
T �
�
j
where
� is the transmitted flux;
�
� is the aperture flux.
j
3.2
transmission density
D
T
logarithm to the base 10 of the reciprocal of the transmittance factor
�
1
j
D��log log
T 10 10
T �
�
3.3
diffusion coefficient
�
dc
measure of the diffusivity of the irradiating or receiving system
NOTE See normative annex A.
4 Coordinate system, terminology and symbols
The coordinate system, terminology and symbols described in ISO 5-1 are used herein as a basis for specifying the
geometric conditions for measurement of transmission density.
5 ISO standard diffuse density
5.1 Geometric modes
Diffuse transmission measurements may be made with a diffuse irradiation source (illuminator) and a directional
receiver, this arrangement being known as the “diffuse influx mode”. Alternatively, measurements may be made
with a directional irradiation source and a diffuse receiver, this arrangement being known as the “diffuse efflux
mode”. The diffuse modes are shown in Figure 1. These modes can be described in terms of a specified diffuse
distribution and a specified directional distribution, the distributions being distributions of radiance or distributions of
sensitivity, depending on the mode.
2 © ISO 2001 – All rights reserved

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SIST ISO 5-2:2002
ISO 5-2:2001(E)
Key Diffuse density measurement
a
(for diffuse influx� =90°,� u 10°)
i �
1 Sampling aperture
a
(for diffuse efflux� u 10°,� =90°)
i �
2 Efflux geometry
3 Point O
Projection density measurement
b
4 Influx geometry (for f /4,5� =� =6,4°)
i �
b
(for f /1,6� =� = 18,2°)
i �
a
The 90° specification implies physical contact between the specimen and the diffuse irradiating system.
b
The values of the half-angle� are calculated using the formula contained in the note of 6.2.
Figure 1 — Geometry for density measurements
5.2 Sampling aperture
The extent and shape of the area on which density is measured is known as the sampling aperture. Physically, the
sampling aperture is realized by a diaphragm which has to be in contact with
...