ISO 5-4:2009

INTERNATIONAL ISO
STANDARD 5-4
Third edition
2009-12-01

Photography and graphic technology —
Density measurements —
Part 4:
Geometric conditions for reflection
density
Photographie et technologie graphique — Mesurages de la densité —
Partie 4: Conditions géométriques pour la densité de réflexion




Reference number
ISO 5-4:2009(E)
©
ISO 2009

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ISO 5-4:2009(E)
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ISO 5-4:2009(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 Distinction between ideal and realized parameters.3
6 Requirements.3
6.1 Influx and efflux geometry.3
6.2 Sampling aperture.4
6.3 Annular distribution .4
6.4 Normal directional distribution.5
6.5 Determination of illuminator radiance distribution.5
6.6 Determination of receiver responsivity distribution.5
6.7 Polarization efficiency.5
6.8 Scattered flux.5
6.9 Backing material.6
6.10 Reference standard.6
6.11 Designation .7
6.12 Conformance testing.7
Annex A (normative) Determining conformance with tolerances.8
Annex B (normative) Determination of accuracy and linearity of a densitometer.9
Annex C (normative) Certified reference materials for measuring instruments with polarizing
means .10
Annex D (normative) Polarization efficiency.11
Annex E (informative) Backing materials .13
Annex F (informative) Reflectance density versus reflectance factor density.14
Bibliography.15

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ISO 5-4:2009(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 2.
The main task of technical committees is to prepare International Standards. 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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 5-4 was prepared by ISO/TC 42, Photography, and ISO/TC 130, Graphic technology, in a Joint Working
Group.
This third edition cancels and replaces the second edition (ISO 5-4:1995), which has been technically revised.
This technical revision introduces the concept of ideal and practical conditions. In the course of this technical
revision, all parts of ISO 5 have been reviewed together, and the terminology, nomenclature and technical
requirements have been made consistent across all parts.
ISO 5 consists of the following parts, under the general title Photography and graphic technology — Density
measurements:
⎯ Part 1: Geometry and functional notation
⎯ Part 2: Geometric conditions for transmittance density
⎯ Part 3: Spectral conditions
⎯ Part 4: Geometric conditions for reflection density
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ISO 5-4:2009(E)
Introduction
This part of ISO 5 specifies the geometric conditions that are used to define ISO 5 standard reflection density
and to make measurements of ISO 5 standard reflection density. These conditions correspond approximately
to practical situations for viewing reflection-type photographs or graphic reproductions, which specifically
requires illuminating the print at an angle of 45° to the normal to the surface and viewing along the normal.
These conditions tend to reduce surface glare and maximize the density range of the image, which is
sometimes referred to as annular 45°:0° reflection densitometry.
The geometric conditions specified in this part of ISO 5 are intended to simulate 45° illumination for viewing or
photographing a specimen. There might be some engineering advantages in designing a measuring
instrument with normal illumination and 45° collection. Reversing the geometry in this way has no
demonstrated effect on the measured values in most cases, so both geometric arrangements are included in
[11]
this part of ISO 5. However, work by Voglesong has demonstrated that there are times when
measurements of the same printed sample with 0°/45° & 45°/0° can be significantly different. This part of
ISO 5 attempts to specify unambiguously the geometric conditions that define reflection densitometry by
providing what is termed “ideal requirements”. The actual design and manufacture of instruments, however,
require tolerances around these ideal conditions which, in this part of ISO 5, are shown as practical
specifications.
This part of ISO 5 serves three primary functions:
a) to provide the basis for unequivocal measurements that are needed for specifications, for communication
between organizations, and for contractual agreements;
b) to provide a reference to assist in resolving seemingly different measurement data between systems; and
c) to aid in the calibration and certification of densitometers, or spectrophotometers used as densitometers,
by allowing for the generation of certified reference materials (CRMs) with numerical values traceable to
fundamental physical phenomena.
For graphic arts applications, guidance in the use of densitometry is provided in ISO 13656.
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INTERNATIONAL STANDARD ISO 5-4:2009(E)

Photography and graphic technology — Density
measurements —
Part 4:
Geometric conditions for reflection density
1 Scope
This part of ISO 5 specifies the geometric conditions for the definition of ISO 5 standard reflection density. It
also recommends tolerances on geometric conditions that can be used in the design of instruments. The
spectral conditions are specified in ISO 5-3.
This part of ISO 5 also specifies the requirements for polarization (if that feature is included) and for backing
material, and makes recommendations regarding accuracy and linearity.
Although intended primarily for use in the measurement of the reflection characteristics of photographic and
graphic arts materials, this part of ISO 5 is also applicable to the measurement of these characteristics for
other materials.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5-1, Photography and graphic technology — Density measurements — Part 1: Geometry and functional
notation
ISO 5-3, Photography and graphic technology — Density measurements — Part 3: Spectral conditions
ISO 13655, Graphic technology — Spectral measurement and colorimetric computation for graphic arts
images
1)
IEC 60050-845:1987 , International Electrotechnical Vocabulary. Lighting

1) IEC 60050-845:1987 is a joint publication with the International Commission on Illumination (CIE). It is identical to
CIE 17.4:1987, International Lighting Vocabulary.
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ISO 5-4:2009(E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 5-1, IEC 60050-845:1987⏐CIE 17.4:1987
and the following apply.
3.1
certified reference material
CRM
reference material, accompanied by a certificate, one or more of whose property values are certified by a
procedure which establishes traceability to an accurate realization of the unit in which the property values are
expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence
NOTE Adapted from ISO Guide 30.
3.2
gloss suppression factor
P
numerical expression of the polarization efficiency of a densitometer with polarizing means
NOTE For a precise definition of P, see Annex D.
3.3
receiver
portion of the densitometer that senses the efflux, including the collection optics and detector
3.4
reflection density
D
R
negative logarithm to the base 10 of the reflectance factor
NOTE The International Commission on Illumination (CIE) designates the measurement referred to as “reflection
density” in ISO 5 as “reflectance factor density”. (See IEC 60050-845:1987⏐CIE 17.4:1987.)
[ISO 5-1:2009, definition 3.19]
3.5
reflectance factor
R
ratio of the reflected flux to the absolute reference reflected flux under the same geometrical and spectral
conditions of measurement
[ISO 5-1:2009, definition 3.17]
3.6
screen ruling
number of image elements, such as dots or lines, per unit of length in the direction which produces the highest
value
NOTE Adapted from ISO 12647-1.
3.7
screen width
reciprocal of screen ruling
NOTE Adapted from ISO 12647-1.
4 Coordinate system, terminology and symbols
The coordinate system, terminology and symbols described in ISO 5-1 are used in this part of ISO 5 as a
basis for specifying the geometric conditions for reflection density measurements.
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ISO 5-4:2009(E)
5 Distinction between ideal and realized parameters
The unambiguous definition of density requires that geometric, as well as spectral, parameters be exactly
specified. However, the practical design and manufacture of instruments require that reasonable tolerances
be allowed for physical parameters. The definition of ISO 5 standard reflection density shall be based on the
ideal value specified for each parameter. The tolerances shown for the realized parameter values represent
allowable variations of these standard parameters, which for many applications have an effect of less
than 0,01 on the density values resulting from measurements made with instruments. A method for
determining conformance of a realized parameter with the tolerances is given in Annex A.
6 Requirements
6.1 Influx and efflux geometry
ISO 5 standard reflection measurements may be made with two equivalent measurement geometries. In the
“annular influx mode”, the geometry of the illuminator is annular and the geometry of the receiver is
directional. In the “annular efflux mode”, the geometry of the illuminator is directional and the geometry of the
receiver is annular. The annular influx mode is illustrated in Figure 1. The annular efflux mode would be
illustrated by Figure 1 if the arrows showing the radiant flux direction were reversed and the labels were
interchanged. The modes can be described in terms of specified annular and directional distributions of
illumination radiance (subscript i) or receiver responsivity (subscript r), depending on the mode. The cone half-
angle κ (lower case Greek kappa, κ) is the angle between the angle of illumination or view (lower case Greek
theta, θ ) and the marginal ray.
The ideal angles of illumination and view and half-angles for the annular influx mode are θ = 45°, θ = 0°,
i r
κ = 5°, and κ = 5°. The realized angles of illumination and view and half-angles for the annular influx mode
i r
are θ = 45° ± 2°, θ = 0° ± 2°, κ = 5° ± 1°, and κ = 5° ± 1°.
i r i r
For the annular efflux mode, the ideal angles of illumination and view and half-angles are θ = 0°, θ = 45°,
i r
κ = 5°, and κ = 5°. The realized angles of illumination and view and half-angles for the annular efflux mode
i r
are θ = 0° ± 2°, θ = 45° ± 2°, κ = 5° ± 1°, and κ = 5° ± 1°.
i r i r

Key
1 influx
2 efflux
3 specimen
NOTE Angles indicated represent the practical tolerances for the half-angle of the cone.
Figure 1 — Geometry of the annular influx mode
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ISO 5-4:2009(E)
6.2 Sampling aperture
The extent and shape of the area on which density is measured are the sampling aperture. Physically, the
sampling aperture is realized by the optical systems of the illuminator and receiver. The size and shape of the
sampling aperture are not critical
a) if no dimension is so large that the influx and efflux geometric conditions vary materially over the sampling
aperture, or
b) if no dimension is so small that the effects of granularity, specimen texture, diffraction, or half-tone dot
structure become significant.
For case b), the diameter of a circular sampling aperture should not be less than 15 times the screen width; it
shall not be less than 10 times the screen width that corresponds to the lower limit for the screen ruling for
which the instrument is recommended by the manufacturer. The area of non-circular sampling apertures shall
not be smaller than that required for circular sampling apertures.
The sampling aperture is defined as the smaller of the illuminator region and the receiver region. Ideally, the
larger shall be greater than the smaller to the extent that any increase in size of the larger region has no effect
on the measurement result. The specimen characteristics over the illuminator region should be the same as
those over the receiver region.
NOTE 1 This requirement prevents lateral diffusion error.
The realized boundary of the larger of the illuminator region and the receiver region shall be outside the
boundary of the smaller by at least 2 mm. Where small sampling apertures are required, this dimension shall
be at least 0,5 mm. The magnitude of the resulting lateral diffusion error should be accepted as part of the
overall measurement uncertainty, or a greater boundary differential should be used.
NOTE 2 These dimensions are an acceptable compromise between the need to measure small areas and a negligible
uncertainty of measurement.
Any physical aperture present in the reference plane that is not used to limit either the illuminator region or
receiver region shall be kept well clear of both the influx and efflux beams.
The ideal illuminator radiance and receiver responsivity distributions shall be uniform over the sampling
aperture. The realized distributions shall be uniform to within 10 %. This can be determined by scanning the
sampling aperture laterally with a geometrically similar aperture, similarly oriented and having dimensions no
more than one-quarter of those of the corresponding dimensions of the sampling aperture. The radiance at
any place on the sampling aperture shall be at least 90 % of the maximum radiance.
NOTE 3 Lack of uniformity is immaterial when uniform specimens are measured, but can be an important source of
error in measurements of non-uniform specimens.
6.3 Annular distribution
The ideal angular distribution of radiance from the illuminator (influx) or of responsivity of the receiver (efflux)
shall be uniform for angles within the cone defined by the illuminator or receiver axis and half-angle and zero
for angles outside the cone. The realized angular distribution shall be uniform to within 10 % within the cone
and less than 2 % of the maximum of the cone distribution outside the cone.
The distribution of radiance from the illuminator or responsivity of the receiver shall be uniform around the
annulus, unless the reflection characteristics of the specimens to be measured do not change as they are
rotated in their own plane, in which case the realized radiance or responsivity need not be uniform around the
annulus.
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ISO 5-4:2009(E)
For applications where specimens have been shown to have only a slight dependency on directional effects
(i.e. if density measurements made at azimuthal angles of 0°, 45°, and 90° differ by an amount that is less
than the tolerance acceptable for the intended application), strict uniform annular distribution may be replaced
by a distribution in which either:
⎯ the illuminator has a directional geometry at two azimuthal angles 90° apart (or, preferably, at more than
two equally spaced azimuthal angles), or
⎯ the receiver has a directional geometry at two azimuthal angles 90° apart (or, preferably, at more than
two equally spaced azimuthal angles).
6.4 Normal directional distribution
The ideal angular distribution of radiance from the illuminator (influx) or of responsivity of the receiver (efflux)
shall be uniform for angles within the cone defined by the half-angles and zero for angles outside the cone.
The realized angular distribution shall be uniform within 10 % within the cone and less than 2 % of the
maximum of the cone distribution outside the cone.
6.5 Determination of illuminator radiance distribution
The illuminator radiance distribution can be determined by placing a receiver having uniform angular response
over a conic distribution with a half-angle of 2° at the centre of the sampling aperture. Anormal angles are
scanned with the receiver both in
...