SIST ISO 5-3:1996

INTERNATIONAL IS0
STANDARD 5-3
Second edition
1995-l I-l 5
Photography - Density measurements -
Part 3:
Spectral conditions
Photographic - Mesurage des dens& -
Par-tie 3: Conditions spectr-ales
Reference number
IS0 5-3:1995(E)

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IS0 5=3:1995(E)
Page
Contents
1
........................................................................................
1 Scope
I
...............................................................
2 Normative references
I
................................................................................
3 Definitions
1
............................................................
4 Density measurements
2
.....................................................................
5 Spectral response
2
.....................................................................
6 Spectral products
2
7 Notation .
2
8 Types of density .
2
81 . .
IS0 visual density
5
. .
82 Printing density
.................... 5
.............................................
8.3 IS0 status A density
5
................................................................
8.4 IS0 status M density
............. 6
..................................................
8.5 IS0 status T density.
6
.................................................................
8.6 IS0 status E density
6
........................................................
8.7 IS0 narrow-band density.
6
..................................................................
8.8 IS0 status I density
11
........................................ ............................
8.9 IS0 type 3 density
11
9 Spectral tolerances .
II
........................................
10 Absolute reference standard (white)
Annexes
12
A Cali bration of densitometer . . . . . . . . . . . . . . . . . . . . . .*.
B Spectral products for IS0 density and relative spectral power
13
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
distributions for influxes
..................... 18
C Sideband rejection .
.................................. ............................................ 19
D Bibliography
0 IS0 1995
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 mrcrofilm, without permrssron In writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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IS0 5=3:1995(E)
@ IS0
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(I EC) on all matters of electrotechnical standardization.
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.
International Standard IS0 5-3 was prepared by Technical Committee
ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (IS0 5-3:1984),
which has been technically revised. It has also been expanded to include
additional spectral types commonly used in consumer, professional, and
graphic arts photographic applications. Status E and status I responses
have been included in view of their relevance to graphic technology.
Annexes A to D of this part of IS0 5 are for information only.

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@ IS0
IS0 5-3: 1995(E)
Introduction
This part of IS0 5 is one of a series which specifies the spectral conditions
for optical densitometry as practised in black-and-white and colour photo-
graphic applications.
To define a density value fully, it is necessary to specify both the geo-
metric and spectral conditions of the measuring system. Geometric con-
ditions are described in IS0 5-2 for transmission density, and in IS0 5-4 for
reflection density. This part of IS0 5 specifies the spectral conditions for
both transmission and reflection density measurements.
In the early years of densitometry, the spectral responses of instruments
were specified only in terms of the colour filters used in the construction.
Although it was seldom the case, it was assumed that the spectral re-
sponses of the photoreceivers and the illuminant spectral energy
distributions as well as all intervening optical components were the same
in all instruments. In more recent times densitometry standards have
specified that the product of all these components must equal some given
set of published “documentary” values. Such a specification allows
flexibility to the manufacturer while providing for improved accuracy and
precision. It also allows for standard reference materials to be manufac-
tured and certified based on fundamental measurements.
In photographic image reproduction, optical density is a measure of the
modulation of light or other radiant flux by a given area of the recording
medium. The measurement of density may be of interest for various
reasons. It may be necessary to assess the lightness or darkness of an im-
age, to predict how a film or paper will perform in a printing operation, or
to determine some measure of the amounts of colorants in the image for
the purpose of controlling a colour process. If the visual effect is of
interest, the spectral conditions of measurement must simulate some ap-
propriate illumination and the spectral sensitivity of the eye. For printing
operations, the spectral power distribution of the irradiator to be used in
the printing operation and the spectral sensitivity of the print material must
be simulated. In evaluating original material for colour separation, the il-
luminant, the spectral sensitivity of the separation medium, and the
spectral transmittance of the tricolour separation filters must be simulated.
Certain types of density measurements are often made to generate sen-
sitometric curves which are used to characterize the photographic
properties of films and papers. Densities can also be used for tone-
reproduction analysis and to monitor various operations such as photo-
processing, lithography, gravure, screen printing processes, etc.
The specified spectral power distribution of the incident flux for trans-
mission density measurements differs from that for reflection density
measurements. For reflection density measurements, incandescent tung-
sten illumination of the type known as CIE (Commission internationale de
I’eclairage) standard illuminant A, adopted by the International Commission
on Illumination in 1931 is specified. Its use in densitometry is preferred be-
cause national standardizing laboratories are generally prepared to make
spectrophotometric measurements and perform calorimetric computa-
tions of visual reflection factors on the basis of CIE standard illuminant A.
This usage facilitates the procurement of physical standards for reflection
iv

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@ IS0 IS0 5=3:1995(E)
densitometry. For transmission density measurements, the spectral distri-
bution of the influx is CIE standard illuminant A, as modified by a typical
heat-absorbing filter to protect the specimen and optical system from
heat.
Many standards for reflection density specify the use of barium sulfate as
the reference standard. However, pressed barium sulfate is fragile, vari-
able from lot to lot of powder, variable from pressing to pressing, and the
reflectance drifts appreciably in the first few days after pressing.
In 1969, the International Commission on Illumination (CIE) recommended
that all reflectance factors and, by inference, the corresponding reflection
densities be reported relative to a perfectly reflecting and perfectly diffus-
ing material.
In day-to-day operation reflection densitometers are usually calibrated with
standard reference materials available from a number of sources. These
working standards are calibrated with respect to primary standards that
are calibrated by absolute methods in national standards laboratories.

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INTERNATIONAL STANDARD @ IS0 IS0 5=3:1995(E)
Photography - Density measurements -
Part 3:
Spectral conditions
NOTES
I Scope
1 Based on the International Practical Temperature Scale,
This part of IS0 5 specifies spectral conditions for the
1968, using Planck’s second constant
measurement of several types of densities used in
c2 = 1,438 8 x 10m2 m-K
photographic image reproduction. Photographic image
reproduction as used throughout this part of IS0 5
2 The radiation of a gas-filled coil tungsten filament lamp
encompasses the broad definition of photography as
operated at a distribution temperature of 2 856 K will
the art or process of producing images on a sensitized
approximate this spectral distribution and thus can serve as
surface by the action of radiant energy.
a practical realization of this standard illuminant.
2 Normative references
3.2 sideband rejection: The degree that radiation
outside a desired passband is blocked or suppressed.
The following standards contain provisions which, It is usually expressed as the ratio of the integrated
through reference in this text, constitute provisions of energy within the desired passband to the integrated
this part of IS0 5. At the time of publication, the energy outside the passband.
editions indicated were valid. All standards are subject
3.3 peak wavelength: That wavelength at which
to revision, and parties to agreements based on this
the system response is a maximum.
part of IS0 5 are encouraged to investigate the
possibility of applying the most recent editions of the
3.4 spectral bandwidth: Width, in wavelength
standards indicated below. Members of IEC and IS0
units, of the response band measured between the
maintain registers of currently valid International
points where the response has fallen to designated
Standards.
percentages of the peak response.
IS0 5-l : 1984, Photography - Density measure-
3.5 influx spectrum: Spectrum of the radiant flux
ments - Part I: Terms, symbols and notations.
incident on the specimen surface or sampling aper-
ture. It is a function of the energy source and the op-
CIE Publication 17.4:1987, International lighting vo-
tical system on the source side of the specimen.
cabulary.
CIE Publication 1821983, The basis of physical pho-
4 Density measurements
tome try.
To define completely a type of density spectrally, it is
3 Definitions
necessary to specify the light source, optics and
spectral response of the measuring system.
For the purposes of this part of IS0 5, the definitions
The basic light source for densitometry is CIE stan-
given in IS0 5-l and the following definitions apply.
dard illuminant A (see 3.1). In some reflection and
almost all transmission densitometers, it is necessary
3.1 CIE standard illuminant A: Planckian radiation
to add a heat-absorbing filter to the influx side to
at a temperature of about 2 856 K?
protect the specimen and optical elements. If the ab-
1) As defined in CIE Publication 17.4.

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0 IS0
IS0 5=3:1995(E)
sorber does not change the relative power distribution ements, it is not necessary to specify the spectral
of CIE A below 550 nm, no significant fluorescence characteristics of the influx and receiver separately, as
lona as the correct spectral products are obtained.
effect should be observed or be of concern.
The spectra products for a densitometer may be de-
noted as:
4.1 Reflection densitometry
n = ss
For reflection density measurements, if either the
where
densitometer manufacturer or the user is not sure of
the absence of fluorescence in the sample to be is t
S le relative spectral power of the influx;
measured, the relative spectral power distribution of
IS the relative spectral response of the
S
the incident flux shall be CIE standard illuminant A
receiver, which includes the photodetector
which is given in table 1 under the heading SA (which
and all intervening components between it
is the symbol used in functional notation).
and the plane of the specimen.
4.2 Transmission densitometry
7 Notation
For transmission density measurements, if either the
densitometer manufacturer or the user is not sure of
IS0 5-1 specifies functional notation of the form
the absence of fluorescence in the sample to be
D(G; S : g; s), where G and g symbolize the influx ge-
measured, the relative spectral power distribution of
ometry and efflux geometry respectively. Since this
the incident flux shall be that given in table 1 under
part of IS0 5 is only concerned with spectral con-
the heading S, (which is the symbol used in functional
ditions, the notation is abbreviated to D(S : s). To
notation). This is based on the spectral power distri-
reflection density (DR) and
distinguish between
bution of the CIE standard illuminant A modified in the
transmission density (D+, a subscript may be used.
infrared region to protect the sample and optical el-
ements from excessive heat which is typical for most
transmission densitometers.
8 Types of density
4.3 Sample conditions
Several spectral types of densitometry are used to
evaluate photographic recording media. These are de-
Some materials change density with variations in tem-
fined in terms of logarithmic spectral product values
perature and relative humidity. Therefore, to avoid am-
specified at 10 nm (nanometre) intervals. Spectral
biguity, specimens shall be at 23 “C & 2 “C and
product, I7, values are obtained by multiplying the
(50 + 5) % e a ive humidity when determining IS0
r I t
relative spectral power values of the densitometer
density.
influx spectrum, S, at IO nm intervals by the relative
spectral response values, s, of the receiver in the per-
tinent wavelength region. The resultant products are
5 Spectral response, s
normalized to yield a peak value of 100 000. The
logarithms to the base 10 of these values are used in
The spectral response of a densitometer is a function
this part of IS0 5 to define the various spectral types.
of the spectral sensitivity of the photodetector and the
spectral modifications by any of the optics and filters
between the plane of the specimen and the photo-
8.1 IS0 visual density, D&SH : VT), DR(SA : V)
detector. Theoretically, it is desirable for the spectral
response to match the spectral sensitivity of the
To evaluate the darkness of an image which is to be
receiver (eye, photographic paper, etc.) used in the
viewed directly or by projection, visual density is
practical applications of the product.
measured. Such measurements are most often made
on black-and-white images, but can be made on other
types of images.
6 Spectral products, 17
For reflection density, the combined spectral sensi-
If the spectral power of the influx spectrum, S, is mul-
tivity of the receiver and the spectral characteristics of
tiplied by the spectral response, S, of the receiver, the components of the efflux section of the densi-
wavelength by wavelength, spectral products are tometer shall match the spectral luminous efficiency
obtained. Since significant fluorescence from a num- function for photopic vision, V(AL2) The product of V(A)
ber of sources is often encountered, it is desirable to and SA, wavelength by wavelength, defines the
conform to the influx spectra specified in this part of spectral products the whole densitometer must have
IS0 5. However, in those cases where there is no in order to provide IS0 visual densities. The
fluorescence in the specimen or in the optical el- logarithms of the products are given in table 2.
2) See CIE Publication 18.2.
2

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IS0 5=3:1995(E)
Table 1 - IS0 densitometer influx spectra
350
360
370
380
390
400
410
420
480
500
510
520
530
550
570 107
114
122
600
136
620 144
630
640 158
650
660
670
680
690
700
710 204
720
730
740
750
760
770
NOTE - Relative spectral power distributions are normalized to 100 at 560 nm.

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IS0 5-3:1995(E)
log,, spectral products for IS0 visual, type 1 and type 2 densities
Table 2 -
(Normalized to 5,000 peak)
Visual
Type 1
TYPe 2
Wavelength
log10 "1
log10 “v log10 n2
A, nm
(Printing: diazo and vesicular)
(Printing: silver halide)
< 1,000
340
350 2,708
360 < 1,000 4,280
1,640 4,583
370
2,860 4,760
380
4,460 4,851
390
< 1,000 5,000 4,916
400
1,322 4,460 4,956
410
1,914 2,860 4,988
420
2,447 1,640 5,000
430
2,811 < 1,000 4,990
440
4,951
450 3,090
4,864
460 3,346
470 3,582 4,743
4,582
480 3,818
490 4,041 4,351
500 4,276 3,993
510 4,513 3,402
520 4,702 2,805
530 4,825 2,211
540 4,905 < 1,000
550 4,957
560 4,989
570 5,000
580 4,989
590 4,956
600 4,902
610 4,827
620 4,731
630 4,593
640 4,433
650 4,238
660 4,013
670 3,749
680 3,490
690 3,188
700 2,901
710 2,622
720
2,334
730 2,041
740 1,732
750 1,431
760
1,146
770 < 1,000
4

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0 IS0
IS0 5=3:1995(E)
The spectral products required for visual transmission 8.2.2 IS0 type 2 firinting density, D&S, : s2)
densitometry are the same as those used for
When printing is done onto non-colour-sensitized
reflection. However, since the influx is different, the
silver halide photographic material (e.g. a black-and-
spectral response of the receiver, VP must compen-
white paper or film), the log spectral products found
S,V at every 10 nm interval.
sate so that S,V, =
useful are indicated as log
1o f12 in table 2. These have
been derived by using the average spectral sensitivity
of a print material as modified by the transmission of
8.2 Printing density 3,
an ultraviolet absorbing filter with a sharp cut-off at
360 nm. The resultant sensitivity is designated s2. The
Printing continuous-tone images onto light-sensitive
filter is included to minimize effects caused by vari-
materials requires a special metric called printing den-
ations in the optics of printing systems, and the
sity. The spectral conditions required for measuring
absorption band of silver deposits at 320 nm. Multiply-
the printing density are a function of the spectral
ing the spectral sensitivity values by the relative spec-
power d
...