ISO/TS 17321-4:2022

ISO/TS 17321-4:2022(E)
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ISO TC 42/JWG 20
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Date: 2022-09-07xx
at 18 pt
Graphic technology and photography — Colour characterization of digital still cameras (DSCs) —
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Part 4: Programmable light emission system
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Élément introductif — Élément central — Partie 4: Élément complémentaire
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Style Definition: ANNEX
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Technologie graphique et photographie — Caractérisation de la couleur des appareils photonumériques
— Partie 4: Système d'émission de lumière programmable

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ISO/TS 17321-4:2022(E)
© ISO 2022
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All rights reserved. Unless otherwise specified, or required in the context of its implementation, no
part of this publication may be reproduced or utilized otherwise in any form or by any means,
electronic or mechanical, including photocopying, or posting on the internet or an intranet, without
prior written permission. Permission can be requested from either ISO at the address below or
ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2022 – All rights reserved

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ISO/TS 17321-4:2022(E)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Description . 2
4.1 General . 2
4.2 Operating condition . 2
4.3 Description of the system . 3
4.3.1 General . 3
4.3.2 Wavelength . 3
4.3.3 Resolution of digital-analogue conversion for light emitting devices . 3
4.3.4 Output window size . 3
4.3.5 Luminance . 3
4.3.6 Uniformity . 3
4.3.7 Angular characteristics . 4
4.3.8 Repeatability . 4
4.4 Reporting form . 5
5 Generation and evaluation of a spectral match . 6
5.1 Generation of a spectral match . 6
5.2 Evaluation of a spectral match . 7
Annex A (informative) Spectral match generation, scaling, and evaluation examples . 8
A.1 Generation . 8
A.2 Scaling . 8
A.3 Evaluation . 8
A.4 Repeatability, constant signal to noise measure . 9
Annex B (informative) Several guideline information to design the PLES . 10
Annex C (informative) An example for the PLES required and recommended conditions . 11
Bibliography . 12
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Description . 2
4.1 General . 2
4.2 Operating condition . 2
4.3 Description of the system . 3
4.3.1 General . 3
4.3.2 Wavelength . 3
© ISO 2022 – All rights reserved iii

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ISO/TS 17321-4:2022(E)
4.3.3 Resolution of digital-analogue conversion for light emitting devices . 3
4.3.4 Output window size . 3
4.3.5 Luminance . 3
4.3.6 Uniformity . 3
4.3.7 Angular characteristics . 4
4.3.8 Repeatability . 4
4.4 Reporting form . 5
5 Generation and evaluation of a spectral match . 6
5.1 Generation of a spectral match . 6
5.2 Evaluation of a spectral match . 7
Annex A (informative) Spectral match generation, scaling, and evaluation examples . 8
Annex B (informative) Several guideline information to design the PLES . 10
Annex C (informative) An example for the PLES required and recommended conditions . 11
Bibliography . 12

iv © ISO 2022 – All rights reserved

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ISO/TS 17321-4:2022(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directiveswww.iso.org/directives).
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. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received (see www.iso.org/patentswww.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO/TS 17321-4:2016), which has been
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technically revised.
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The main changes are as follows:
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— reorganized introduction and clauseClause 4.;
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— clauseClause 4 is concentrated on the hardware evaluation of programmable light emission system Formatted: Pattern: Clear
(PLES). And new annexesNew Annexes B and C arewere added to the second edition.;
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— added a new clauseClause 5 and a new annexAnnex A using VSA (Vector Space Arithmetic)
formulation for simpler-conceptual explanation of spectral match for PLES. were added;
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— removed unnecessary explanations on spectral generation (annexesAnnexes A, B, C, D, E, F and
explanation of spectral match in clauseClause 4), accordingly. Formatted: Pattern: Clear
Formatted: cite_app
A list of all parts in the ISO 17321 series can be found on the ISO website.
Formatted: Pattern: Clear
Any feedback or questions on this document should be directed to the user’s national standards body. A
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complete listing of these bodies can be found at
Formatted: Pattern: Clear
www.iso.org/members.htmlwww.iso.org/members.html.
Formatted: Pattern: Clear
© ISO 2022 – All rights reserved v

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ISO/TS 17321-4:2022(E)
Introduction
This part of ISO 17321document describes a programmable light emission system. This system may be
used to create spectra that are arbitrary combinations of the lights contained within or may be used to
create a spectral match to a target reference spectrum. Unless the lights are of high dimensionality (ideal
spectral shape at each wavelength) such a match will generally be only approximate. Therefore,
evaluation methods for the spectra generated by the system are also described.
An example hardware description of a programmable light emission system is presented in
clauseClause 4. While any programmable light emission system that meets the tolerances specified may
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be utilized, this document considers systems comprised of light emitting devices such as inorganic or
organic LEDs, quantum dots, and laser diodes (if equipped with suitable spatial filtering).
vi © ISO 2022 – All rights reserved

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TECHNICAL SPECIFICATION ISO/TS 17321-4:2022(E)

Graphic technology and photography — Colour characterization
of digital still cameras (DSCs) — Part 4: Programmable light
emission system
1 Scope
This part of ISO 17321document describes a programmable light emission system to produce various
spectral radiance distributions, intended for DSC colour characterization applications.
Commented [eXtyles1]: eXtyles Inline Standards Citation
Match reports that the normative reference
"ISO 12646:2015" is not cited in the text.
2 Normative references
Commented [eXtyles2]: The match came back with a
different title. The original title was: Colorimetry — Part 5:
The following documents are referred to in the text in such a way that some or all of their content
CIE 1976 L*u*v* Colour space and u′, v′ uniform
constitutes requirements of this document. For dated references, only the edition cited applies. For
chromaticity scale diagram
undated references, the latest edition of the referenced document (including any amendments) applies.
Commented [eXtyles3]: eXtyles Inline Standards Citation
ISO 7589, Photography — Illuminants for sensitometry — Specifications for daylight, incandescent
Match reports that the normative reference
"ISO/CIE 11664-5:2016" is not cited in the text.
tungsten and printer
Formatted: English (United States)
ISO 12646:2015, Graphic technology — Displays for colour proofing — Characteristics
Formatted: Adjust space between Latin and Asian text,
Adjust space between Asian text and numbers
ISO/CIE 11664-5:2016, Colorimetry — Part 5: CIE 1976 L*u*v* colour space and u', v' uniform
chromaticity scale diagram
Formatted: Font: Times New Roman, 12 pt, English
(United States)
CIE S 017:2020, ILV: International Lighting Vocabulary, 2nd Edition
Commented [eXtyles4]: URL Validation failed:
https://www.iso.org/obp returns an unknown connection
ISO 7589, Photography — Illuminants for sensitometry — Specifications for daylight, incandescent
failure. (connection error "Error 12031:
ERROR_INTERNET_CONNECTION_RESET").
tungsten and printer
Formatted: English (United States)
ISO/CIE 11664-5, Colorimetry — Part 5: CIE 1976 L*u*v* colour space and u', v' uniform chromaticity scale
Formatted: Adjust space between Latin and Asian text,
diagram
Adjust space between Asian text and numbers, Tab
stops: Not at 19.85 pt + 39.7 pt + 59.55 pt + 79.4 pt
3 Terms and definitions
+ 99.25 pt + 119.05 pt + 138.9 pt + 158.75 pt +
178.6 pt + 198.45 pt
For the purposes of this document, the following terms and definitions apply.
Formatted: Hyperlink, English (United States)
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
Formatted: English (United States)
— ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
Formatted: Hyperlink, English (United States)
Commented [eXtyles5]: The term "colour-matching
— IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
functions" has not been used anywhere in this document
3.1 Formatted: Pattern: Clear
colour-matching functions
Formatted: std_publisher
tristimulus values (3.5) of monochromatic stimuli of equal radiant flux
Formatted: std_docNumber
[SOURCE: CIE S 017:2020, 17-23-039]
Formatted: std_docNumber
Formatted: std_year
3.2
Formatted: std_section
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ISO/TS 17321-4:2022(E)
digital still camera
DSC
device which incorporates an image sensor, and which produces a digital signal representing a still
picture
Note 1 to entry: A digital still camera is typically a portable, hand-held device. The digital signal is usually recorded
on a removable memory, such as a solid-state memory card or magnetic disk.
[SOURCE: ISO 17321-1:2012., 3.2] Formatted: Pattern: Clear
Formatted: Pattern: Clear
3.3
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light-emitting diode
LED Formatted: std_year
semiconductor diode that emits non coherent optical radiation through stimulated emission resulting
Formatted: std_section
from the recombination electrons and photons, when excited by an electric current
Commented [eXtyles6]: The term "light-emitting diode"
has not been used anywhere in this document
Note 1 to entry: SeeFor an example of LED, CIE S 017:2020, 17-27-050 shall be referred to.
Formatted: Font: Not Italic
[SOURCE: IEC 60050- 521:2002, 521-04-39]
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3.4
programmable light emission system
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PLES
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system that produces various spectral radiance distributions using light emitting devices
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3.5
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tristimulus values
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amounts of the reference colour stimuli, in a given trichromatic system, required to match the colour of
the stimulus considered
Commented [eXtyles7]: Invalid reference: "IEC 60050-
521"
Note 1 to entry: See colour matching functions (3.1).
Commented [eXtyles8]: eXtyles Inline Standards Citation
Match has detected that the standard reference "IEC 60050-
[SOURCE: CIE S 017:2020, 17-23-038] 521, 521-04-39" refers a specific part of an undated standard.
Because part numbers may change between editions, please
check the part number for accuracy or change to a dated
4 Description
reference.
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4.1 General
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Figure 1 shows a cross-section of an example of a programmable light emission system (PLES). An
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integrating sphere in the Figure 1 is utilized to ensure good spatial uniformity for the light emission. Light
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emitting devices are placed at the bottom and an output window is placed on the side to allow the mixed
light to be emitted. The ability to measure absolute XYZ values is a requirement. A tele-
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spectrophotometer is one of such measurement methods to obtain these values and used to verify the
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accuracy of the generated spectra.
Formatted: std_publisher
There are many kinds of light emitting devices. For example, if LEDs are used for the light emitting
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devices, the LEDs are electrically modulated and the emitted flux will be mixed (integrated) by multiple
reflections from the inner surface of the sphere, in order to produce a required spectral distribution of
Formatted: std_docNumber
light flux.
Formatted: std_year
17321-4_ed2fig1.EPS Formatted: std_section
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2 © ISO 2022 – All rights reserved

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ISO/TS 17321-4:2022(E)

Key
1 output window
2 light emitting device array
3 integrating sphere
a
Uniform light emission on the output window.
Figure 1 — Schematic configuration of the programmable light emission system (PLES)
Annex B shows LED driving methods of the PLES.
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As a more compact alternative to integrating sphere, flat panel diffusers can also be designed to produce
near-uniform output by the light levels of the individual LED modules.
4.2 Operating condition
The light emitting system shall be designed to operate consistently under the ranges described in Table 1.
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Table 1 — Operating conditions
Operating condition Range
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Temperature 18 °C to 28 °C
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Relative humidity 15 % to 80 %
NOTE The temperature requiresrequirements were taken from ISO 12646 Displays for colour proofing –
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Characteristics.
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4.3 Description of the system
4.3.1 General
This clause describes the PLES. An example for the PLES conditions areis described in Annex C.
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Warm-up time shall be chosen to be long enough so that the system has reached stable state and
stabilized at the desired operating temperature after power-on of the PLES. And itIt is recommended that
a default spectral distribution is outputted during warm-up time in order to reduce warm-up time. This
warm-up time is applied to all of spectral distribution measurement.
© ISO 2022 – All rights reserved 3

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ISO/TS 17321-4:2022(E)
Every spectral measurement shall be performed after 5- s to 10 secondss when the PLES outputs
different spectral distribution.
4.3.2 Wavelength
The wavelength range over which the combined set of the light emissive devices is evaluated should be
at least broad enough to cover the range of spectral sensitivity of the DSC of interest and shall be specified.
Generally, this will be 380 nm to 730 nm though longer wavelengths into the near-infrared should be
included.
4.3.3 Resolution of digital-analogue conversion for light emitting devices
Sufficient resolution of digital-analogue conversion shall be used assuming that the PLES is setup such
that there is a linear relationship between the power applied to each light emitting device and the
resulting intensity from each light emitting device.
NOTE ReferSee Annex C for more information.
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4.3.4 Output window size
The output window (see Figure 1) shall be large enough for the intended use.
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NOTE ReferSee Annex C for more information.
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4.3.5 Luminance
The maximum luminance of the output window shall have sufficient luminance when simulating various
light sources including fluorescent and LED light sources.
NOTE ReferSee Annex C for more information.
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4.3.6 Uniformity
For circular shaped output windows, luminance is measured at the centre and at 8 points evenly spaced
next to the circumference of the output window at 45° intervals. The luminance measurements are made
normal to the plane of the output window at each measurement point.
17321-4_ed2fig2.EPS

Figure 2 — Measurement points on the output window with every 45°
Figure 2 shows measurement points on the output window to calculate uniformity characteristics.
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Uniformity is defined by the Formula (1):
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4 © ISO 2022 – All rights reserved

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ISO/TS 17321-4:2022(E)
Y −Y Y −Y Formatted: Adjust space between Latin and Asian text,
i ave i ave
∆=Y max x100 Y max ×100 (1)
u u Adjust space between Asian text and numbers, Tab
ic∈°,0 ~315° Y ic∈°,0 ~315° Y
ave ave
stops: Not at 19.85 pt + 39.7 pt + 59.55 pt + 79.4 pt
+ 99.25 pt + 119.05 pt + 138.9 pt + 158.75 pt +
where, Y is the average of the luminance measured on the output window. Y is the luminance measured
ave i 178.6 pt + 198.45 pt
either at centre or at each location next to the circumference of the output window.
Field Code Changed
where
Y is the average of the luminance measured on the output window;
ave
Yi is the luminance measured either at centre or at each location next to the circumference of the
output window.
NOTE ReferSee Annex C for more information.
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4.3.7 Angular characteristics
The luminance is measured within a 10° cone angle to the normal line of the centre of the output window.
An integrating sphere could be used in order to ensure uniformity across the output window. Figure 3
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shows angular characteristic measurement method. It is the typical method for a colour target having an
arrangement of an output window and light sources shown in Figure 1.
Formatted: Pattern: Clear
17321-4_ed2fig3.EPS

Key
1 output window
Figure 3 — Angular characteristics measurement method
Y −Y
i nor
∆Y =max (2)
θ
i∈+θθ, − Y
nor
Where, Y is luminance measured along the axis normal to the output window, Y or Y isThe
nor +θ -θ Formatted: Adjust space between Latin and Asian text,
luminance measured along the axis which is inclined +θ or -θ to the normal axis, respectively. Maximum
Adjust space between Asian text and numbers
θ is 5° of arc. is given by Formula (2):
Y −Y Field Code Changed
i nor
∆Y =max (2)
θ
i∈+θθ, − Y
nor
where
© ISO 2022 – All rights reserved 5

∆=

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ISO/TS 17321-4:2022(E)
Y is the luminance measured along the axis normal to the output window;
nor
Y or Y is the luminance measured along the axis which is inclined +θ or -θ to the normal axis, respectively.
+θ -θ
Maximum θ is 5° of arc. Formatted: Pattern: Clear
NOTE ReferSee Annex C for more information.
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4.3.8 Repeatability
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4.3.8.1 General
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There are two use cases for measuring the light intensity repeatability performance. The first one is short- Formatted: Font: Not Italic
term repeatability for continuous use within a day described in 4.3.8.2 where suffix “ ” is used. The
S
Formatted: Font: Not Italic
second is long-term repeatability for intermittent use on day to day described in 4.3.8.3 where suffix “ ”
L
Formatted: Font: Not Italic
is used.
Formatted: Font: Not Italic
4.3.8.2 Short-term repeatability
Formatted
...
The following specifies the method for characterizing method for continuous use repeatability.
Formatted: Pattern: Clear
Step 1: Generate a spectral match to CIE illuminant D55 (in accordance with ISO 7589) using the light
Formatted: Pattern: Clear
2
emitting system with a recommended luminance level of close to 400 cd/m . The actual luminance shall
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be reported.
Formatted: Font: Italic
Step 2: Allow the system to warm-up for an optimum time to reach stable state.
Formatted: Font: Not Italic
Step 3: Measure the absolute XYZ tristimulus values every five minutes for a total of seven sets of X Y Z
i i i
Formatted: Font: Italic
tristimulus values. Suffix i (i= = 1,7) describes seven different measurements per one day. And calculate
mean YS, mean value using seven Yi data.
Formatted: Font: Not Italic
NOTE The XYZ tristimulus values are simply calculated using convolution operation of the colour-matching Formatted: Font: Italic
function and spectral distribution.
Formatted: Font: Not Italic
Formatted: Font: Not Italic
Step 4: Calculate u ’ and v ’ chromaticity using the absolute X Y Z tristimulus values:
S S i i i
Formatted: Font: Italic
u′ = 4X / (X ++15Y 3Z )
i i i ii
(3)
Formatted: Font: Not Italic
v′ = 9Y / (X ++15Y 3Z )
Formatted: Font: Italic
i i i ii
(4)
Formatted: Font: Not Italic
Refer ISO/CIE 11664-5 for u’ and v’ calculation.
Formatted: Font: Italic
Step 5: Calculate standard deviations σ(Y ), σ(u ’) and σ(v ’) of the 7 measurements. Formatted: Font: Not Italic
S S S
Formatted: Pattern: Clear
Step 6: Report Y , σ(Y ), σ(u ’) and σ(v ’).
S, mean S S S
Formatted: Font: Not Italic
4.3.8.3 Long-term repeatability
Formatted: Font: Not Italic
The following specifies the method for characterizing intermittent use repeatability.
Formatted: Font: Not Italic
Steps 1 to 2 described in 4.3.8.2 are repeated seven times over the course of seven different days. Power
Formatt
...

TECHNICAL ISO/TS
SPECIFICATION 17321-4
Second edition
Graphic technology and
photography — Colour
characterization of digital still
cameras (DSCs) —
Part 4:
Programmable light emission system
Technologie graphique et photographie — Caractérisation de la
couleur des appareils photonumériques —
Partie 4: Système d'émission de lumière programmable
PROOF/ÉPREUVE
Reference number
ISO/TS 17321-4:2022(E)
© ISO 2022 – All rights reserved

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ISO/TS 17321-4:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
PROOF/ÉPREUVE © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/TS 17321-4:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Description . .2
4.1 General . 2
4.2 Operating condition . 3
4.3 Description of the system . 3
4.3.1 General . 3
4.3.2 Wavelength . 4
4.3.3 Resolution of digital-analogue conversion for light emitting devices . 4
4.3.4 Output window size . 4
4.3.5 Luminance . 4
4.3.6 Uniformity . 4
4.3.7 Angular characteristics . . 5
4.3.8 Repeatability . 5
4.4 Reporting form . 6
5 Generation and evaluation of a spectral match . 7
5.1 Generation of a spectral match . 7
5.2 Evaluation of a spectral match . 8
Annex A (informative) Spectral match generation, scaling, and evaluation examples .9
Annex B (informative) Several guideline information to design the PLES .11
Annex C (informative) An example for the PLES required and recommended conditions .12
Bibliography .13
iii
© ISO 2022 – All rights reserved PROOF/ÉPREUVE

---------------------- Page: 3 ----------------------
ISO/TS 17321-4:2022(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO/TS 17321-4:2016), which has been
technically revised.
The main changes are as follows:
— reorganized introduction and Clause 4;
— Clause 4 is concentrated on the hardware evaluation of programmable light emission system (PLES).
New Annexes B and C were added to the second edition;
— a new Clause 5 and a new Annex A using VSA (Vector Space Arithmetic) formulation for simpler-
conceptual explanation of spectral match for PLES were added;
— removed unnecessary explanations on spectral generation (Annexes A, B, C, D, E, F and explanation
of spectral match in Clause 4), accordingly.
A list of all parts in the ISO 17321 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
PROOF/ÉPREUVE © ISO 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/TS 17321-4:2022(E)
Introduction
This document describes a programmable light emission system. This system may be used to create
spectra that are arbitrary combinations of the lights contained within or may be used to create a spectral
match to a target reference spectrum. Unless the lights are of high dimensionality (ideal spectral shape
at each wavelength) such a match will generally be only approximate. Therefore, evaluation methods
for the spectra generated by the system are also described.
An example hardware description of a programmable light emission system is presented in Clause 4.
While any programmable light emission system that meets the tolerances specified may be utilized,
this document considers systems comprised of light emitting devices such as inorganic or organic LEDs,
quantum dots, and laser diodes (if equipped with suitable spatial filtering).
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TECHNICAL SPECIFICATION ISO/TS 17321-4:2022(E)
Graphic technology and photography — Colour
characterization of digital still cameras (DSCs) —
Part 4:
Programmable light emission system
1 Scope
This document describes a programmable light emission system to produce various spectral radiance
distributions, intended for DSC colour characterization applications.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 7589, Photography — Illuminants for sensitometry — Specifications for daylight, incandescent
tungsten and printer
ISO/CIE 11664-5, Colorimetry — Part 5: CIE 1976 L*u*v* colour space and u', v' uniform chromaticity scale
diagram
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
colour-matching functions
tristimulus values (3.5) of monochromatic stimuli of equal radiant flux
[SOURCE: CIE S 017:2020, 17-23-039]
3.2
digital still camera
DSC
device which incorporates an image sensor, and which produces a digital signal representing a still
picture
Note 1 to entry: A digital still camera is typically a portable, hand-held device. The digital signal is usually
recorded on a removable memory, such as a solid-state memory card or magnetic disk.
[SOURCE: ISO 17321-1:2012, 3.2]
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ISO/TS 17321-4:2022(E)
3.3
light-emitting diode
LED
semiconductor diode that emits non coherent optical radiation through stimulated emission resulting
from the recombination electrons and photons, when excited by an electric current
Note 1 to entry: For an example of LED, CIE S 017:2020, 17-27-050 shall be referred to.
[SOURCE: IEC 60050-521:2002, 521-04-39]
3.4
programmable light emission system
PLES
system that produces various spectral radiance distributions using light emitting devices
3.5
tristimulus values
amounts of the reference colour stimuli, in a given trichromatic system, required to match the colour of
the stimulus considered
Note 1 to entry: See colour matching functions (3.1).
[SOURCE: CIE S 017:2020, 17-23-038]
4 Description
4.1 General
Figure 1 shows a cross-section of an example of a programmable light emission system (PLES). An
integrating sphere in the Figure 1 is utilized to ensure good spatial uniformity for the light emission.
Light emitting devices are placed at the bottom and an output window is placed on the side to allow
the mixed light to be emitted. The ability to measure absolute XYZ values is a requirement. A tele-
spectrophotometer is one of such measurement methods to obtain these values and used to verify the
accuracy of the generated spectra.
There are many kinds of light emitting devices. For example, if LEDs are used for the light emitting
devices, the LEDs are electrically modulated and the emitted flux will be mixed (integrated) by multiple
reflections from the inner surface of the sphere, in order to produce a required spectral distribution of
light flux.
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ISO/TS 17321-4:2022(E)
Key
1 output window
2 light emitting device array
3 integrating sphere
a
Uniform light emission on the output window.
Figure 1 — Schematic configuration of the programmable light emission system (PLES)
Annex B shows LED driving methods of the PLES.
As a more compact alternative to integrating sphere, flat panel diffusers can also be designed to produce
near-uniform output by the light levels of the individual LED modules.
4.2 Operating condition
The light emitting system shall be designed to operate consistently under the ranges described in
Table 1.
Table 1 — Operating conditions
Operating condition Range
Temperature 18 °C to 28 °C
Relative humidity 15 % to 80 %
NOTE The temperature requirements were taken from ISO 12646.
4.3 Description of the system
4.3.1 General
This clause describes the PLES. An example for the PLES conditions is described in Annex C.
Warm-up time shall be chosen to be long enough so that the system has reached stable state and
stabilized at the desired operating temperature after power-on of the PLES. It is recommended that a
default spectral distribution is outputted during warm-up time in order to reduce warm-up time. This
warm-up time is applied to all of spectral distribution measurement.
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ISO/TS 17321-4:2022(E)
Every spectral measurement shall be performed after 5 s to 10 s when the PLES outputs different
spectral distribution.
4.3.2 Wavelength
The wavelength range over which the combined set of the light emissive devices is evaluated should
be at least broad enough to cover the range of spectral sensitivity of the DSC of interest and shall be
specified. Generally, this will be 380 nm to 730 nm though longer wavelengths into the near-infrared
should be included.
4.3.3 Resolution of digital-analogue conversion for light emitting devices
Sufficient resolution of digital-analogue conversion shall be used assuming that the PLES is setup such
that there is a linear relationship between the power applied to each light emitting device and the
resulting intensity from each light emitting device.
NOTE See Annex C for more information.
4.3.4 Output window size
The output window (see Fig
...