Ergonomics of human-system interaction - Part 391: Requirements, analysis and compliance test methods for the reduction of photosensitive seizures (ISO 9241-391:2016)

ISO 9241-391:2016 provides requirements and recommendations for reducing photosensitive seizures (PSS), while viewing images on electronic displays.
The requirements and recommendations in this part of ISO 9241 are designed to be applied to image contents. By image contents, reference is made to the images independent of the device or environment in which they are displayed.
The requirements and recommendations in this part of ISO 9241 are for the protection of the vulnerable individuals in the viewing population who are photosensitive and who are therefore liable to seizures triggered by flashing lights and regular patterns, including certain repetitive images.
NOTE 1       ITU considers the image safety issues in relation to broadcasting. Some of these are described in ITU-R BT.1702.[2]
NOTE 2       There are some related recommendations in ISO/IEC 40500:2012, W3C Web Content Accessibility Guidelines (WCAG) 2.0, for web contents accessibility.
NOTE 3       Photosensitive seizures and photosensitive epilepsy, that is, chronic conditions characterized by those repeated seizures are medical conditions. Clinical aspects of photosensitivity appear in Annex C. Visually induced seizures are equivalent to PSS.

Ergonomie der Mensch-System-Interaktion - Teil 391: Anforderungen, Analysen und Prüfverfahren zur Konformität zur Verringerung epileptischer Anfälle aufgrund photosensitiver Reize (ISO 9241-391:2016)

Dieser Teil von ISO 9241 stellt Anforderungen und Empfehlungen zur Verminderung von Anfällen aufgrund photosensitiver Reize (PSS) bei der Betrachtung von Bildern auf elektronischen Anzeigegeräten bereit.
Die Anforderungen und Empfehlungen dieses Teils von ISO 9241 wurden für die Anwendung auf Bildinhalte entwickelt. Durch den Begriff „Bildinhalte“ wird auf die Bilder selber verwiesen, unabhängig von Anzeigegerät oder Umgebung, innerhalb derer sie angezeigt werden.
Die Anforderungen und Empfehlungen dieses Teils von ISO 9241 sind zum Schutz der verletzlichen Personen innerhalb der Bevölkerung gedacht, die lichtempfindlich sind und die daher anfällig für Anfälle, die durch aufblitzende Lichter und regelmäßige Muster, einschließlich bestimmter, sich wiederholender Bilder, ausgelöst werden.
ANMERKUNG 1   Die Internationale Fernmeldeunion (ITU) befasst sich mit den Sicherheitsaspekten von Bildern in Bezug auf deren Ausstrahlung. Einige dieser Aspekte werden in ITU-R BT.1702 [2] beschrieben.
ANMERKUNG 2   In ISO/IEC 40500:2012 [W3C Web Content Accessibility Guidelines (WCAG) 2.0] gibt es einige damit verbundene Empfehlungen hinsichtlich des Zugangs zu Inhalten des Internets.
ANMERKUNG 3   Anfälle aufgrund photosensitiver Reize und epileptische Anfälle bedeutet, dass die durch die wiederholten Anfälle gekennzeichneten, chronischen Zustände medizinische Zustände sind. Auf die klinischen Aspekte der Photosensibilität wird in Anhang C Bezug genommen. Visuell hervorgerufene Anfälle sind äquivalent zu PSS.

Ergonomie de l'interaction homme-système - Partie 391: Exigences, analyses et méthodes d'essai de conformité pour la réduction des saisies photosensibles (ISO 9241-391:2016)

ISO 9241-391:2016 spécifie des exigences et fournit des recommandations concernant la réduction des saisies photosensibles (SPS) lors de l'observation d'images sur des afficheurs électroniques.
Les exigences et les recommandations dans la présente partie de l'ISO 9241 sont destinées à être appliquées à des contenus d'images. Le terme «contenus d'images» fait référence aux images elles-mêmes, indépendamment du dispositif ou de l'environnement sur (dans) lequel elles sont affichées.
Les exigences et les recommandations fournies dans la présente partie de l'ISO 9241 sont destinées à la protection de la partie vulnérable de la population, qui risque de faire des crises d'épilepsie photosensible déclenchées par des flashs lumineux et des séquences répétitives, y compris certaines images répétitives.
NOTE 1       L'UIT étudie les problèmes liés à la sécurité des images par rapport à la télédiffusion. Certaines d'entre elles sont décrites dans la Recommandation UIT-R BT.1702.[2]
NOTE 2       Quelques recommandations pertinentes sont fournies dans l'ISO/IEC 40500:2012, Technologies de l'information ? Règles pour l'accessibilité des contenus Web (WCAG) 2.0 du World Wide Web Consortium (W3C) pour l'accessibilité des contenus Web.
NOTE 3       Les saisies photosensibles et l'épilepsie photosensible, c'est-à-dire des troubles chroniques caractérisés par des crises répétées, constituent des états pathologiques. Les aspects cliniques de la photosensibilité sont abordés dans l'Annexe C. Les crises induites par stimulus visuel sont équivalentes aux saisies photosensibles (SPS).

Ergonomija medsebojnega vpliva človek-sistem - 391. del: Zahteve, analize in preskusne metode za ugotavljanje skladnosti za zmanjšanje epileptičnih napadov, sproženih s fotosenzitivnimi dražljaji (ISO 9241-391:2016)

Ta del standarda ISO 9241 podaja smernice za zmanjševanje epileptičnih napadov, sproženih s fotosenzitivnimi dražljaji, enega od treh največjih neželenih biomedicinskih učinkov, ki jih sprožajo slike, predstavljene na elektronskih vizualnih zaslonih. Smernice opisujejo pogoje, ki jih v osnovi ustvarjajo elektronske vizualne slikovne vsebine, predstavljene v domačih in delovnih okoljih, vendar ne na elektronskih vizualnih zaslonih. Smernica v dokumentu je namenjena zaščiti ranljivega dela populacije gledalcev, ki so občutljivi na fotosenzitivne dražljaje ter so zato nagnjeni k epileptičnim napadom, ki jih sprožijo utripajoče lučke in enakomerni vzorci, vključno z določenimi vrstami ponavljajočih slik.

General Information

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Published
Publication Date
01-Mar-2016
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
02-Mar-2016
Completion Date
02-Mar-2016

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SLOVENSKI STANDARD
SIST EN ISO 9241-391:2016
01-junij-2016
(UJRQRPLMDPHGVHERMQHJDYSOLYDþORYHNVLVWHPGHO=DKWHYHDQDOL]HLQ
SUHVNXVQHPHWRGH]DXJRWDYOMDQMHVNODGQRVWL]D]PDQMãDQMHHSLOHSWLþQLKQDSDGRY
VSURåHQLKVIRWRVHQ]LWLYQLPLGUDåOMDML ,62
Ergonomics of human-system interaction - Part 391: Requirements, analysis and
compliance test methods for the reduction of photosensitive seizures (ISO 9241-
391:2016)
Ergonomie der Mensch-System-Interaktion - Teil 391: Anforderungen, Analysen und

Prüfverfahren zur Konformität zur Verringerung epileptischer Anfälle ausgelöst durch

photosensitive Reize (ISO 9241-391:2016)
Ergonomie de l'interaction homme-système - Partie 391: Exigences, analyses et

méthodes d'essai de conformité pour la réduction des saisies photosensibles (ISO 9241-

391:2016)
Ta slovenski standard je istoveten z: EN ISO 9241-391:2016
ICS:
11.020.99 Drugi standardi v zvezi z Other standards related to
zdravstvom na splošno health care in general
13.180 Ergonomija Ergonomics
SIST EN ISO 9241-391:2016 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 9241-391:2016
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SIST EN ISO 9241-391:2016
EN ISO 9241-391
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2016
EUROPÄISCHE NORM
ICS 13.180; 35.180
English Version
Ergonomics of human-system interaction - Part 391:
Requirements, analysis and compliance test methods for
the reduction of photosensitive seizures (ISO 9241-
391:2016)

Ergonomie de l'interaction homme-système - Partie Ergonomie der Mensch-System-Interaktion - Teil 391:

391: Exigences, analyses et méthodes d'essai de Anforderungen, Analysen und Prüfverfahren zur

conformité pour la réduction des saisies Konformität zur Verringerung epileptischer Anfälle

photosensibles (ISO 9241-391:2016) ausgelöst durch photosensitive Reize (ISO 9241-

391:2016)
This European Standard was approved by CEN on 19 December 2015.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9241-391:2016 E

worldwide for CEN national Members.
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SIST EN ISO 9241-391:2016
EN ISO 9241-391:2016 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 9241-391:2016
EN ISO 9241-391:2016 (E)
European foreword
This document (EN ISO 9241-391:2016) has been prepared by Technical Committee

ISO/TC 159 “Ergonomics” in collaboration with Technical Committee CEN/TC 122 “Ergonomics” the

secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by September 2016, and conflicting national standards

shall be withdrawn at the latest by September 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent

rights.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
Endorsement notice

The text of ISO 9241-391:2016 has been approved by CEN as EN ISO 9241-391:2016 without any

modification.
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SIST EN ISO 9241-391:2016
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SIST EN ISO 9241-391:2016
INTERNATIONAL ISO
STANDARD 9241-391
First edition
2016-02-01
Ergonomics of human-system
interaction —
Part 391:
Requirements, analysis and
compliance test methods for the
reduction of photosensitive seizures
Ergonomie de l’interaction homme-système —
Partie 391: Exigences, analyses et méthodes d’essai de conformité
pour la réduction des saisies photosensibles
Reference number
ISO 9241-391:2016(E)
ISO 2016
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SIST EN ISO 9241-391:2016
ISO 9241-391:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, 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

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ISO copyright office
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ii © ISO 2016 – All rights reserved
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SIST EN ISO 9241-391:2016
ISO 9241-391:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..............................................................................................................................................................................................................................vii

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Image factors of photosensitive seizures .................................................................................................................................... 2

5 Ergonomic requirements and recommendations .............................................................................................................. 3

5.1 General ........................................................................................................................................................................................................... 3

5.2 Flashes ............................................................................................................................................................................................................ 3

5.2.1 Potentially harmful flashes ..................................................................................................................................... 3

5.2.2 Rapid changes of image sequences .................................................................................................................. 4

5.2.3 Potentially harmful red flashes ........................................................................................................................... 4

5.2.4 Cumulative risk ................................................................................................................................................................. 4

5.2.5 Prior warning ...................................................................................................................................................................... 4

5.3 Potentially harmful regular patterns ................................................................................................................................... 4

6 Conformance ............................................................................................................................................................................................................. 5

6.1 General ........................................................................................................................................................................................................... 5

6.2 Test methods ............................................................................................................................................................................................. 5

6.3 Procedure of conformance............................................................................................................................................................ 6

Annex A (informative) Overview of the ISO 9241-series ................................................................................................................ 7

Annex B (informative) Abbreviated terms ..................................................................................................................................................... 8

Annex C (informative) Clinical aspects of photosensitivity ......................................................................................................... 9

Annex D (informative) Viewing environments ......................................................................................................................................10

Annex E (informative) Saturated red ...............................................................................................................................................................11

Annex F (informative) Typical relation between screen luminance and signal voltage .............................12

Annex G (informative) Sample procedure for assessing applicability and conformance .........................13

Bibliography .............................................................................................................................................................................................................................15

© ISO 2016 – All rights reserved iii
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SIST EN ISO 9241-391:2016
ISO 9241-391:2016(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 on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical

Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information.

The committee responsible for this document is ISO/TC 159, Ergonomics, Subcommittee SC 4, Ergonomics

of human-system interaction.

ISO 9241 consists of the following parts, under the general title Ergonomic requirements for office work

with visual display terminals (VDTs):
— Part 1: General introduction
— Part 2: Guidance on task requirements
— Part 5: Workstation layout and postural requirements
— Part 6: Guidance on the work environment
— Part 11: Guidance on usability
— Part 12: Presentation of information
— Part 13: User guidance
— Part 14: Menu dialogues
— Part 15: Command dialogues
— Part 16: Direct manipulation dialogues

ISO 9241 also consists of the following parts, under the general title Ergonomics of human-system

interaction:

— Part 20: Accessibility guidelines for information/communication technology (ICT) equipment and services

— Part 100: Introduction to standards related to software ergonomics [Technical Report]

— Part 110: Dialogue principles
iv © ISO 2016 – All rights reserved
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SIST EN ISO 9241-391:2016
ISO 9241-391:2016(E)
— Part 112: Principles for the presentation of information
— Part 129: Guidance on software individualization
— Part 143: Forms
— Part 151: Guidance on World Wide Web user interfaces
— Part 154: Interactive voice response (IVR) applications
— Part 161: Guidance on visual user-interface elements
— Part 171: Guidance on software accessibility
— Part 210: Human-centred design for interactive systems

— Part 220: Processes for enabling, executing and assessing human-centred design within organizations

— Part 300: Introduction to electronic visual display requirements
— Part 302: Terminology for electronic visual displays
— Part 303: Requirements for electronic visual displays
— Part 304: User performance test methods for electronic visual displays
— Part 305: Optical laboratory test methods for electronic visual displays
— Part 306: Field assessment methods for electronic visual displays
— Part 307: Analysis and compliance test methods for electronic visual displays

— Part 308: Surface-conduction electron-emitter displays (SED) [Technical Report]

— Part 309: Organic light-emitting diode (OLED) displays [Technical Report]

— Part 310: Visibility, aesthetics and ergonomics of pixel defects [Technical Report]

— Part 331: Optical characteristics of autostereoscopic displays [Technical Report]

— Part 391: Requirements, analysis and compliance test methods for the reduction of photosensitive seizures

— Part 392: Ergonomic recommendations for the reduction of visual fatigue from stereoscopic images

— Part 400: Principles and requirements for physical input devices
— Part 410: Design criteria for physical input devices

— Part 411: Evaluation methods for the design of physical input devices [Technical Specification]

— Part 420: Selection of physical input devices
— Part 910: Framework for tactile and haptic interaction
— Part 920: Guidance on tactile and haptic interactions
— Part 940: Evaluation of tactile and haptic interactions
— Part 960: Framework and guidance for gesture interactions
The following parts are under preparation:
— Part 125: Guidance on visual presentation of information
1) To be published.
© ISO 2016 – All rights reserved v
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ISO 9241-391:2016(E)
— Part 333: Stereoscopic displays using glasses
For the other parts under preparation, see Annex A.
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SIST EN ISO 9241-391:2016
ISO 9241-391:2016(E)
Introduction

Recent progress of technology enables us to watch high-definition images, some of which can be

stereoscopic. When those images are projected onto the retina of both eyes and processed as visual

information, undesirable biomedical effects, such as photosensitive seizures, visually induced motion

sickness, and visual fatigue from stereoscopic images can be induced. These undesirable biomedical

effects need to be reduced where feasible. The prevention of these undesirable biomedical effects on

human health has been referred to as “image safety”.

Image safety was first discussed by the ISO in the ISO/COPOLCO with respect to the users of image

products. Then, in 2004, the ISO/International Workshop on Image Safety was held and resulted

[1]

in the publication of ISO/IWA 3:2005 as the international workshop agreement. Following those

discussions, the study group (ISO/TC 159/SC 4/SG on Image Safety) continued to evaluate strategies

of the international standardizations until 2009. The basic concept of Image Safety is common with

[18]

ISO/IEC Guide 71:2014 , in which the idea is that accessibility to and usability of products and

services should be available to all people.

This part of ISO 9241 will help promote the production of safer images by reducing the risk of

photosensitive seizures, and thereby result in the wider distribution of images that are free from

constraints on which consumers can view them. A small proportion of the population is susceptible to

seizures and other neurological effects when watching motion picture and video content with certain

display features. Since these reactions depend on individual susceptibility have been documented with

programming viewed through cathode-ray tube (CRT) displays, there is as yet less experience with

high-definition displays.

This part of ISO 9241 belongs to a family of human-system interaction standards. Readers who need

guidance on other aspects of human-system interaction should refer to the ISO 9241-series.

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SIST EN ISO 9241-391:2016
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SIST EN ISO 9241-391:2016
INTERNATIONAL STANDARD ISO 9241-391:2016(E)
Ergonomics of human-system interaction —
Part 391:
Requirements, analysis and compliance test methods for
the reduction of photosensitive seizures
1 Scope

This part of ISO 9241 provides requirements and recommendations for reducing photosensitive

seizures (PSS), while viewing images on electronic displays.

The requirements and recommendations in this part of ISO 9241 are designed to be applied to image

contents. By image contents, reference is made to the images independent of the device or environment

in which they are displayed.

The requirements and recommendations in this part of ISO 9241 are for the protection of the vulnerable

individuals in the viewing population who are photosensitive and who are therefore liable to seizures

triggered by flashing lights and regular patterns, including certain repetitive images.

NOTE 1 ITU considers the image safety issues in relation to broadcasting. Some of these are described in

[2]
ITU-R BT.1702.

NOTE 2 There are some related recommendations in ISO/IEC 40500:2012, W3C Web Content Accessibility

Guidelines (WCAG) 2.0, for web contents accessibility.

NOTE 3 Photosensitive seizures and photosensitive epilepsy, that is, chronic conditions characterized by

those repeated seizures are medical conditions. Clinical aspects of photosensitivity appear in Annex C. Visually

induced seizures are equivalent to PSS.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 9241-302, Ergonomics of human-system interaction — Part 302: Terminology for electronic visual displays

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 9241-302 and the

following apply.
3.1
flash
pair of opposing changes in relative luminance

Note 1 to entry: A “pair of opposing changes” is an increase followed by a decrease or a decrease followed by an

increase.
3.2
electroencephalogram
EEG

record of electrical changes caused by neuronal activities in the brain through electrodes attached to

the scalp
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ISO 9241-391:2016(E)
3.3
photoparoxysmal response
PPR

EEG (3.2) response to flash (3.1) or pattern, consisting of spikes, spike–waves, or intermittent slow

waves, which include spike-waves at around 3 Hz that can be detected bilaterally and simultaneously in

all areas of the scalp
3.4
photosensitivity

human individual sensitivity to flashing or intermittent light stimulation and/or visual patterns,

evidenced by the occurrence of a photoparoxysmal response (3.3) in the EEG (3.2)

Note 1 to entry: Visual sensitivity is a term recently sometimes used as an alternative to the term

“photosensitivity.”
3.5
photosensitive seizure
PSS
[3]

epileptic seizure triggered by visual stimulation as a result of photosensitivity (3.4) in a human individual

3.6
photosensitive epilepsy

chronic neurological condition characterized by recurrent photosensitive seizures (3.5), either

convulsive or non-convulsive seizures, such as absence seizures
4 Image factors of photosensitive seizures

A photosensitive seizure may be produced in susceptible individuals by flashing lights or certain

[3][16]

regular patterns. A visual stimulus tending to provoke a seizure is bright light flashes of a certain

[4]

number per second. The light must also fill a large part of the visual field. For the light flashes, colour

[5][12]

changes to or from saturated red, instead of luminance changes, also tend to provoke a seizure.

Another potentially provocative visual stimulus for some individuals with photosensitivity is regular

[6]

patterns with a certain number of bright stripes per a certain area. The pattern must also fill a

large part of the visual field, while the provocation depends on whether the patterns are stationary or

[7][16][17]
oscillating (including flashing).
[3][14]

PSS can be reduced, to some extent, by considering factors such as those shown below. These

[13][15]
factors need to be considered at the same time in an appropriate balance.
— Potentially harmful flashes:
— Luminance and contrast
— Area of visual field
— Number of flashes per unit time
— Rapid changes of image sequences
— Potentially harmful red flashes:
— Colour
— Area of visual field
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ISO 9241-391:2016(E)
— Number of flashes per unit time
— Cumulative risk:
— Duration of flashing
— Potentially harmful regular patterns:
— Clearly discernible stripes
— Number of stripes and area of visual field occupied
— Moving/stationary
— Luminance and contrast
— Duration of patterns
5 Ergonomic requirements and recommendations
5.1 General

To obtain the condition that will sufficiently reduce the possibility of PSS, visual content, viewing

environment, and characteristics of viewers need to be considered. However, in this part of ISO 9241,

characteristics of visual content, such as flashing and regular patterns, are the principal concern. For

viewing environment to be considered, Annex D provides the information.

The requirements in 5.2.1 to 5.2.3 are based on a wide range of flash rates and differences in brightness

that have been demonstrated to cause PPRs in almost all photosensitive individuals, although each such

individual is likely to respond to a narrower set of flash rates and brightness changes within that range.

A small number of subjects, however, recorded PPRs at slower flash rates and others may be susceptible

to smaller changes in brightness. A photosensitive individual’s susceptibility to visual stimuli may

vary with environmental factors and changing individual physical conditions. Therefore, even if visual

content complies with the requirements in this part of ISO 9241 that does not preclude the possibility

that some photosensitive individuals may have a PPR or PSS when viewing that content. The purpose

of this part of ISO 9241 is to reduce the incidence of such events substantially through a framework for

producers of the content that is reasonably practical to comply with.

NOTE 1 The following principles in 5.2 and 5.3 are easier to apply in the case of pre-recorded content, which

can be analysed frame-by-frame. Interactive media, such as video games, may afford essentially limitless

sequences through the game, depending upon user actions. In the case of video games, the requirements and

[8]

recommendations apply to typical sequences of play, but cannot cover every eventuality of play.

NOTE 2 The requirements and recommendations are based on the data obtained with the maximum screen

2 [15]
luminance of 200 cd/m and below, and the maximum screen size of 60 in.
5.2 Flashes
5.2.1 Potentially harmful flashes

Potentially harmful flashes shall be avoided. Potentially harmful flashes are defined as those satisfying

all the following conditions.

a) A pair of opposing changes in luminance (i.e. an increase in luminance followed by a decrease or a

decrease followed by an increase) of 20 cd/m or more when the luminance of the darker image is

below 160 cd/m .

b) The combined area of flashes, satisfying (a) above, occurring concurrently, occupies more than one

quarter of the displayed screen area.
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c) There are more than 3 flashes and fewer than 65 flashes within any one-second period.

Potentially harmful flashes can be produced by playing images at fast speed. Therefore, it is useful for

viewers to be informed of this possibility.
5.2.2 Rapid changes of image sequences

Rapidly changing image sequences (for example, “fast cuts”, see Note below), shall be avoided if they

result in areas of the screen that produce a potentially harmful flash.

NOTE “Fast cuts” denote switching briefly and abruptly from one scene to another in movies, videos, and

other image products.
5.2.3 Potentially harmful red flashes

Potentially harmful red flashes shall be avoided, irrespective of luminance change. Potentially harmful

red flashes are defined as those satisfying all the following conditions.

a) A transition between a saturated red and a colour differing more than 0,2 in CIE 1976 UCS

chromaticity diagram.

b) The combined area of red flashes, satisfying (a) above, occurring concurrently, occupies more than

one quarter of the displayed screen area.

c) There are more than 3 red flashes and fewer than 65 red flashes, those satisfying (a) above, within

any one-second period.

NOTE 1 Saturated red can be defined in the CIE chromaticity diagram (see Annex E).

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NOTE 2 Increment of colour difference can increase incidence of PPR.
5.2.4 Cumulative risk

It should be noted that the level of any cumulative risk arising from successive sequences of “potentially

harmful” flashes over a prolonged period is unknown. If, as medical opinion suggests, the risk of

seizures increases with the duration of flashing, it should be noted that a sequence of flashing images

lasting more than 5 s might constitute a risk, even when it complies with 5.2.1 to 5.2.3.

5.2.5 Prior warning

If it is not possible to correct the image or to check all possible image sequences to meet the requirements

in 5.2.1 to 5.2.3, then a prior warning shall be given.
5.3 Potentially harmful regular patterns

Potentially harmful regular patterns should be avoided. Potentially harmful regular patterns are

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defined as those satisfying all the following conditions.

a) Clearly discernible stripes, which may be parallel or radial, curved or straight, in any orientation.

b) If the patterns are stationary, the stripes are more than eight light-dark pairs occupying more

than 40 % of the displayed screen area, or if the pattern changes direction, oscill

...

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