EN ISO 9241-303:2011

Ergonomics of human-system interaction - Part 303: Requirements for electronic visual displays (ISO 9241-303:2011)

ISO 9241-303:2011 establishes image-quality requirements, as well as providing guidelines, for electronic visual displays. These are given in the form of generic (independent of technology, task and environment) performance specifications and recommendations that will ensure effective and comfortable viewing conditions for users with normal or adjusted-to-normal eyesight.

Ergonomie der Mensch-System-Interaktion - Teil 303: Anforderungen an elektronische optische Anzeigen (ISO 9241-303:2011)

Dieser Teil von ISO 9241 legt Anforderungen an die Bildqualität von elektronischen optischen Anzeigen fest und enthält entsprechende Leitlinien. Diese sind als generelle, von Technologie, Aufgaben und Umgebung unabhängige Leistungsspezifikationen und Empfehlungen festgelegt, um effektive und komfortable Seh-bedingungen für Anwender mit normaler oder auf normal korrigierter Sehschärfe sicherzustellen.
Dieser Teil von ISO 9241 betrifft nicht die Verfügbarkeit für Menschen mit Behinderungen. Sie berücksichtigt aber Aspekte der Sehschärfe älterer Menschen und kann für Menschen von Bedeutung sein, die sich mit Fragen der Sehbehinderung in bestimmten Fällen beschäftigen; die Spezifikation wesentlicher Merkmale der Normalsicht kann zur Beurteilung der Schwere verschiedener Sehanomalien verwendet werden, um geeig¬nete Lösungen aufzuzeigen.
ANMERKUNG   Darüber hinaus enthalten die Literaturhinweise im Anhang F eine Auswahl einschlägiger Dokumente, die sich mit den Bedürfnissen von Menschen mit Behinderungen einschließlich derjenigen beschäftigen, die ein geringes, sich verschlechterndes oder kein Sehvermögen haben.

Ergonomie de l'interaction homme-système - Partie 303: Exigences relatives aux écrans de visualisation électroniques (ISO 9241-303:2011)

L'ISO 9241-303:2011 établit des exigences de qualité d'image, et donne des lignes directrices, pour les écrans de visualisation électroniques. Ces exigences et lignes directrices sont génériques (elles sont indépendantes de la technologie, de la tâche et de l'environnement). Elles sont énoncées sous forme de spécifications et de recommandations de performance pour garantir des conditions de visualisation efficaces et confortables aux utilisateurs disposant d'une vision normale ou ajustée de manière à être normale.

Ergonomija medsebojnega vpliva človek-sistem - 303. del: Zahteve za elektronske slikovne zaslone (ISO 9241-303:2011)

Ta del standarda ISO 9241 določa zahteve v zvezi s kakovostjo slike ter smernice za elektronske slikovne zaslone. Podane so v obliki generičnih priporočil in specifikacij lastnosti, neodvisnih od tehnologije, naloge in okolja, ki zagotavljajo učinkovite in udobne pogoje gledanja za uporabnike z normalnim vidom ali vidom, prilagojenim normalnemu. Ta del standarda ISO 9241 ne obravnava dostopnosti za invalide. Vendar pa upošteva vidike v zvezi z vidom starejših ljudi in je lahko v nekaterih primerih koristen za ljudi, ki se ukvarjajo s prizadetostjo vida: specifikacija osnovnih značilnosti za običajno gledanje se lahko uporablja za merjenje resnosti različnih anomalij v zvezi z vidom za prepoznavanje ustreznih rešitev.

General Information

• Status: Published
• Publication Date: 14-Nov-2011
• ICS: 13.180 - Ergonomics
• ICS: 35.180 - IT Terminal and other peripheral equipment
• Technical Committee: CEN/TC 122 - Ergonomics
• Drafting Committee: CEN/TC 122/WG 5 - Ergonomics of human-computer interaction
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 15-Nov-2011
• Completion Date: 15-Nov-2011
• Ref Project: SIST EN ISO 9241-303:2012 - Ergonomics of human-system interaction - Part 303: Requirements for electronic visual displays (ISO 9241-303:2011)

Relations

• Replaces: EN ISO 9241-303:2008 - Ergonomics of human-system interaction - Part 303: Requirements for electronic visual displays (ISO 9241-303:2008)
• Effective Date: 25-Dec-2010

Standards Content (Sample)

SLOVENSKI STANDARD
01-marec-2012
1DGRPHãþD
SIST EN ISO 9241-303:2009
(UJRQRPLMDPHGVHERMQHJDYSOLYDþORYHNVLVWHPGHO=DKWHYH]DHOHNWURQVNH
VOLNRYQH]DVORQH,62
Ergonomics of human-system interaction - Part 303: Requirements for electronic visual
displays (ISO 9241-303:2011)
Ergonomie der Mensch-System-Interaktion - Teil 303: Anforderungen an elektronische
optische Anzeigen (ISO 9241-303:2011)
Ergonomie de l'interaction homme-système - Partie 303: Exigences relatives aux écrans
de visualisation électroniques (ISO 9241-303:2011)
Ta slovenski standard je istoveten z: EN ISO 9241-303:2011
ICS:
13.180 Ergonomija Ergonomics
35.180 Terminalska in druga IT Terminal and other
periferna oprema IT peripheral equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 9241-303
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2011
ICS 13.180; 35.180 Supersedes EN ISO 9241-303:2008
English Version
Ergonomics of human-system interaction - Part 303:
Requirements for electronic visual displays (ISO 9241-303:2011)
Ergonomie de l'interaction homme-système - Partie 303: Ergonomie der Mensch-System-Interaktion - Teil 303:
Exigences relatives aux écrans de visualisation Anforderungen an elektronische optische Anzeigen (ISO
électroniques (ISO 9241-303:2011) 9241-303:2011)
This European Standard was approved by CEN on 10 November 2011.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 9241-303:2011: E
worldwide for CEN national Members.

Contents Page
Foreword .3

Foreword
This document (EN ISO 9241-303:2011) 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 May 2012, and conflicting national standards shall be withdrawn at the
latest by May 2012.
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.
This document supersedes EN ISO 9241-303:2008.
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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 9241-303:2011 has been approved by CEN as a EN ISO 9241-303:2011 without any
modification.
INTERNATIONAL ISO
STANDARD 9241-303
Second edition
2011-11-15
Ergonomics of human-system
interaction —
Part 303:
Requirements for electronic visual
displays
Ergonomie de l'interaction homme-système —
Partie 303: Exigences relatives aux écrans de visualisation
électroniques
Reference number
ISO 9241-303:2011(E)
©
ISO 2011
ISO 9241-303:2011(E)
©  ISO 2011
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 microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2011 – All rights reserved

ISO 9241-303:2011(E)
Contents Page
Foreword . v
Introduction . viii
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Guiding principles . 1
5  Ergonomic requirements and recommendations . 2
5.1  Viewing conditions . 2
5.1.1  General . 2
5.1.2  Design viewing distance . 2
5.1.3  Design viewing direction . 3
5.1.4  Gaze and head tilt angles . 4
5.1.5  Displays for virtual images . 4
5.2  Luminance . 4
5.2.1  General . 4
5.2.2  Illuminance . 4
5.2.3  Display luminance . 4
5.2.4  Luminance balance and glare . 5
5.2.5  Luminance adjustment . 5
5.3  Special physical environments . 5
5.3.1  General . 5
5.3.2  Vibration . 5
5.3.3  Wind and rain . 6
5.3.4  Excessive temperatures . 6
5.4  Visual artefacts . 6
5.4.1  General . 6
5.4.2  Luminance non-uniformity . 6
5.4.3  Colour non-uniformity . 6
5.4.4  Contrast uniformity . 7
5.4.5  Geometric distortions . 8
5.4.6  Screen and faceplate defects . 8
5.4.7  Temporal instability (flicker) . 8
5.4.8  Spatial instability (jitter) . 9
5.4.9  Moiré effects . 9
5.4.10  Other instabilities . 10
5.4.11  Unwanted reflections . 10
5.4.12  Unintended depths effects . 10
5.5  Legibility and readability . 11
5.5.1  General . 11
5.5.2  Luminance contrast . 11
5.5.3  Image polarity . 11
5.5.4  Character height . 11
5.5.5  Text size constancy . 12
5.5.6  Character stroke width . 13
5.5.7  Character width-to-height ratio . 13
5.5.8  Character format . 13
5.5.9  Between-character spacing . 13
5.5.10  Between-word spacing . 13
5.5.11  Between-line spacing . 13
ISO 9241-303:2011(E)
5.6  Legibility of information coding .14
5.6.1  General .14
5.6.2  Luminance coding .14
5.6.3  Blink coding .14
5.6.4  Colour coding .14
5.6.5  Geometrical coding .14
5.7  Legibility of graphics .14
5.7.1  General .14
5.7.2  Monochrome and multicolour object size .14
5.7.3  Contrast for object legibility .15
5.7.4  Colour considerations for graphics .15
5.7.5  Background and surrounding image effects .16
5.7.6  Number of colours .16
5.8  Fidelity .17
5.8.1  General .17
5.8.2  Colour gamut and reference white .17
5.8.3  Gamma and grey scale .17
5.8.4  Rendering of moving images .18
5.8.5  Image formation time (IFT) .19
5.8.6  Spatial resolution .19
5.8.7  Raster modulation or fill factor .19
5.8.8  Pixel density .20
6  Conformance .20
Annex A (informative) Overview of the ISO 9241 series .21
Annex B (informative) Attractivity, or subject visual quality .22
Annex C (informative) Usability aspects of installation .23
Annex D (normative) Basic concepts of visual perception for contrast and luminance of
electronic displays .25
Annex E (informative) Virtual display — Performance objectives .33
Annex F (informative) Electronic visual display accessibility — Selected bibliography .40
Bibliography .42

iv © ISO 2011 – All rights reserved

ISO 9241-303:2011(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 9241-303 was prepared by Technical Committee ISO/TC 159, Ergonomics, Subcommittee SC 4,
Ergonomics of human-system interaction.
This second edition cancels and replaces the first edition (ISO 9241-303:2008), of which it constitutes a minor
revision. Together with ISO 9241-302 and ISO 9241-305, ISO 9241-303:2008 cancelled and replaced
ISO 9241-8, and together with ISO 9241-302, ISO 9241-305 and ISO 9241-307, it cancelled and replaced
ISO 9241-7 and ISO 13406-2, and partially replaced ISO 9241-3:
 terms and definitions related to electronic visual displays were transferred to, and collected in,
ISO 9241-302;
 while the areas previously covered in ISO 9241 and by ISO 13406 remained essentially unchanged, test
methods and requirements were updated to account for advances in science and technology;
 all generic ergonomic requirements were incorporated into ISO 9241-303;
 the application of those requirements to different display technologies, application areas and
environmental conditions — including test methods and pass/fail criteria — is specified in ISO 9241-307.
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 4: Keyboard requirements
 Part 5: Workstation layout and postural requirements
 Part 6: Guidance on the work environment
 Part 9: Requirements for non-keyboard input devices
 Part 11: Guidance on usability
ISO 9241-303:2011(E)
 Part 12: Presentation of information
 Part 13: User guidance
 Part 14: Menu dialogues
 Part 15: Command dialogues
 Part 16: Direct manipulation dialogues
 Part 17: Form filling 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
 Part 129: Guidance on software individualization
 Part 143: Forms
 Part 151: Guidance on World Wide Web user interfaces
 Part 171: Guidance on software accessibility
 Part 210: Human-centred design for interactive systems
 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 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 Specifiction]
 Part 420: Selection of physical input devices
vi © ISO 2011 – All rights reserved

ISO 9241-303:2011(E)
 Part 910: Framework for tactile and haptic interaction
 Part 920: Guidance on tactile and haptic interactions
The following parts are under preparation:
 Part 154: Interactive voice response (IVR) applications
Human-centred design and evaluation methods, optical characteristics of autostereoscopic displays, and
requirements, analysis and compliance test methods for the reduction of photosensitive seizures are to form
the subjects of future parts 230, 331 and 391.
ISO 9241-303:2011(E)
Introduction
This part of ISO 9241 addresses a large range of technologies, tasks and environments.
ISO 9241 was originally developed as a seventeen-part International Standard on the ergonomics
requirements for office work with visual display terminals. As part of the standards review process, a major
restructuring of ISO 9241 was agreed to broaden its scope, to incorporate other relevant standards and to
make it more usable. The general title of the revised ISO 9241, “Ergonomics of human-system interaction”,
reflects these changes and aligns the standard with the overall title and scope of Technical Committee
ISO/TC 159, Subcommittee SC 4. The revised multipart standard is structured as series of standards
numbered in the “hundreds”: the 100 series deals with software interfaces, the 200 series with human-centred
design, the 300 series with visual displays, the 400 series with physical input devices, and so on.
See Annex A for an overview of the entire ISO 9241 series.

viii © ISO 2011 – All rights reserved

INTERNATIONAL STANDARD ISO 9241-303:2011(E)

Ergonomics of human-system interaction —
Part 303:
Requirements for electronic visual displays
1 Scope
This part of ISO 9241 establishes image-quality requirements, as well as providing guidelines, for electronic
visual displays. These are given in the form of generic — independent of technology, task and environment —
performance specifications and recommendations that will ensure effective and comfortable viewing
conditions for users with normal or adjusted-to-normal eyesight.
This part of ISO 9241 does not address issues of accessibility for people with disabilities. However, it does
take into account aspects of the eyesight of older people and could be of value to people dealing with issues
of visual impairment in certain cases: the specification of essential characteristics for normal viewing can be
used to gauge the severity of different visual abnormalities so that appropriate solutions can be identified.
NOTE In addition to the Bibliography, Annex F gives a selected bibliography of documents addressing the needs of
people with disabilities, including people with poor, deteriorating or no eyesight.
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 9241-302, Ergonomics of human-system interaction — Part 302: Terminology for electronic visual
displays
ISO 9241-307, Ergonomics of human-system interaction — Part 307: Analysis and compliance test methods
for electronic visual displays
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 9241-302 apply.
4 Guiding principles
For a satisfying human–display interaction, a number of different requirements have to be met at the same
time in an appropriate balance. For the purposes of this part of ISO 9241, these requirements have been
grouped into the following eight major areas:
 viewing conditions;
 luminance;
 special physical environments;
ISO 9241-303:2011(E)
 visual artefacts;
 legibility and readability;
 legibility of information coding;
 legibility of graphics;
 fidelity.
NOTE For the attractivity of the image on the visual display, see Annex B.
5 Ergonomic requirements and recommendations
5.1 Viewing conditions
5.1.1 General
Many tasks require that the information presented on an electronic visual display be acted upon. Viewing the
display such that this information can be taken up quickly, without error and with little effort, is thus highly
important. A number of viewing conditions that are necessary, though not sufficient of themselves, can be
specified for achieving fast, error-free and near-effortless viewing. These pertain to the design viewing
distance and direction and to the needed gaze and head tilt angles of the viewer.
It is known that viewing distance and line-of-sight angle (gaze angle) need to be compatible with the user's
vergence and accommodation capability and his or her capability to focus on short distances.
5.1.2 Design viewing distance
The design viewing distance is dependent on the task and on the electronic visual display and shall not be
less than 300 mm, being the typical minimum comfortable viewing distance, or near point, for normal
(emmetropic) eyes of adults. There is a physiologically determined relationship between the near point and
the age of the user, shown in Figure 1, and between the near point and the luminance level; however, there is
a large variance in this relation.
Shorter viewing distances, of between 200 mm and 300 mm, can be observed in children and (very) young
adults, enabling them to see details (e.g. parts of characters) smaller than those that they could see at greater
distances, provided that aspects such as display luminance, contrast and the sharpness are high enough.
However, most adults as well as older people position their displays at a larger viewing distance, typically
300 mm and more.
For larger visual displays, such as those used in office tasks, the preferred viewing distance is longer —
typically 400 mm to 750 mm. At this distance, the accommodative strain to the eyes is less than at shorter
viewing distances; moreover, there is larger freedom of movement at larger viewing distances. For
presentation tasks or projection, the preferred viewing distance is still larger (typically 2 m to 10 m).
2 © ISO 2011 – All rights reserved

ISO 9241-303:2011(E)
Key
X age, in years
Y1 accommodation span, dioptres
Y2 near point of accommodation, centimetres
1 maximum
2 mean
3 minimum
Figure 1 — Accommodation span and near point in relation to age of user
5.1.3 Design viewing direction
For normal use in which the user moves his or her head, a display shall be legible from any angle of
inclination up to at least 40° from the normal to the surface of the display, measured in any plane.
Depending on the task, other limit values are possible. For example, for tasks requiring privacy, such as
display use in crowded environments, the display should be only legible to a maximum angle of inclination
between 15° and 20°.
EXAMPLE People in wheelchairs wishing to withdraw cash from an automatic teller machine in privacy are obliged
to read the ATM display from a fairly low viewpoint. Their requirements can be met by a display that is only legible to a
maximum angle of inclination between 15° and 20° in the horizontal plane, but downwards to a larger angle, of at least 40°,
in the vertical plane.
ISO 9241-303:2011(E)
NOTE Some display technologies exhibit anisotropic optical properties, which means that the luminance, contrast
and colour vary with viewing direction.
5.1.4 Gaze and head tilt angles
For a typical working environment with an approximately vertical position of the upper body, the work place
and the visual display should permit the user to view the screen with a gaze angle from 0° to 40° and a
head-tilt angle of from 0° to 25°.
NOTE These angle values can require the tilt of the display to be adjustable, so that perpendicular view can be
obtained. In addition, the height (above floor level) of the display might have to be adjustable.
5.1.5 Displays for virtual images
The ergonomics of displays for virtual images are considered in Annex E, covering the ergonomics
characteristics of binocular non-see-through displays and gives recommended values.
5.2 Luminance
5.2.1 General
In order for information symbols on a visual display screen to be visible, sufficient contrast with their
background is necessary. Both symbols and screen background therefore need to be of a certain, different
luminance and/or colour.
In most cases, there is a luminous environment to the screen that contributes to its luminance and colour;
therefore, the contrast on the screen is changed by the luminous environment (for reflective displays such as
paper, contrast on the display screen is even caused by the luminous environment). Since the environment’s
luminosity generally cannot be controlled by the user, it is necessary to provide means of adjusting display
luminance to obtain a proper luminance balance over a range of work environments.
5.2.2 Illuminance
The supplier shall specify the design screen illuminance, E .
S
NOTE If the application uses colours, their chromaticity coordinates, u,v, may change as a result of the colour of the
design screen illumination.
5.2.3 Display luminance
In the ambient illumination for which the display is designed, the display luminance shall exceed the minimum
value for obtaining a sufficient recognizability of the displayed information over the design viewing range and
the intended lifetime of the visual display unit. Under night-time conditions, it should not be so high as to
annihilate dark adaptation of the user’s eyes.
Annex D presents a treatise on basic concepts of contrast and luminance in visual perception. Equation (D.11)
defines the minimum value of bright parts of a display taking into account the luminances of the dark parts and
of diffuse and specular reflections on the display surface.
EXAMPLE For an office application having 500 lx illuminance (horizontally) of white paper with a reflectance of 80 %
2 2
and positive display polarity, it is often recommended that the display luminance be in the range of 100 cd/m to 150 cd/m .
4 © ISO 2011 – All rights reserved

ISO 9241-303:2011(E)
5.2.4 Luminance balance and glare
a) The area average luminance of task areas that are frequently viewed in sequence while using the display
(paper document, screen, etc.) should be between 0,1L and 10L, where L is the average luminance of the
whole screen in the application used on the display in the design viewing direction. For a stationary visual
field, a higher ratio of space average luminances between the task area and its surrounds (for instance,
room walls), up to 1:10, has no adverse effect.
b) The design of the visual display screen and surrounding visible area of the product housing shall not
contribute to disturbing glare by the environmental lighting. This holds especially for prolonged viewing in
work environments.
The visual display screen shall be in accordance with 5.4.11. [The Member States of the European Union
have adopted regulations related to glare and reflections on the workstation, including the display screen
[23]
equipment based on Directive 90/270/EEC (see NOTE 4).]
NOTE 1 Glare is defined by CIE (845-02-52; glare) as: “condition of vision in which there is discomfort or a reduction in
the ability to see details or objects, caused by an unsuitable distribution or range of luminance, or too extreme contrasts”
(see Reference [22]). Disturbing glare thus is a condition of vision in which there is a disturbing degree of visual discomfort
or/and a noticeable reduction in the ability to see details or objects.
NOTE 2 Matt surfaces typically do not produce glare, whereas gloss surfaces can, depending on design aspects such
as shape, colour, size and environmental lighting conditions. There are, however, cases where gloss is advantageous. For
printed paper and displays, such as reflective colour displays, gloss is necessary for obtaining high colour fidelity, whereas
the occurrence of disturbing glare can be avoided by changing the orientation of the paper or display with respect to the
environmental light source.
NOTE 3 For prolonged viewing in work environments, the aim is to harmonize the visual display screen and
surrounding area of the product housing with their environment and its lighting according to ISO 8995-1 and ISO 9241-6.
NOTE 4 Directive 90/270/EEC Annex, 2. (b) requires that “possible disturbing glare and reflections on the screen or
other equipment shall be prevented by coordinating workplace and workstation layout with the positioning and technical
characteristics of the artificial light sources” and Annex, 2. (c) requires that “workstations shall be so designed that sources
of light, such as windows and other openings, transparent or translucid walls, and brightly coloured fixtures or walls cause
no direct glare and no distracting reflections on the screen”.
NOTE 5 The issue of disturbing glare on the visible part of the screen housing is under discussion with regard to a
future revision or amendment of this part of ISO 9241.
5.2.5 Luminance adjustment
For emissive displays, the luminance of the background and/or the contrast between the characters and their
background shall be easily adjustable by the user. The emissive display shall be easily adjustable to ambient
conditions over the range of luminances that can occur in the particular work environment.
5.3 Special physical environments
5.3.1 General
The following guidelines should be taken into consideration in the design of a display wherever it is expected
that the display will be subjected to one or more of the environmental conditions described in 5.3.2 to 5.3.4.
5.3.2 Vibration
Vibration of the display with respect to the head and therefore the eyes (or vice versa) is an annoying effect
that can even reduce visual performance, because
 vibration hampers eye movement control during reading by making it more difficult to determine the target
of saccades, and causing image movement during a fixation pause, in which the centre of the visual field
needs to be recognized,
ISO 9241-303:2011(E)
 the contrast of small details is reduced because the zones along a border will have the average
luminance of both sides of the border, and
 the rapid alternation of light and dark in an area of the visual field can create flicker effects.
The severity of these effects depends on the frequency and amplitude of the vibration. Frequencies above
0,5 Hz of the display are disturbing when their amplitude is more than a threshold value. Also, frequencies of
the head above 6 Hz are disturbing when the amplitude is more than a threshold value. Such frequencies and
amplitudes should therefore be avoided — for example, by embedding the display in appropriate damping
material.
5.3.3 Wind and rain
Strong winds can cause vibrations of objects such as visual displays that are sufficiently exposed.
Rain drops falling on a display screen will distort the displayed image, to the point where text becomes
illegible.
Visual displays that may be used outdoors should therefore be mechanically shielded from such weather
effects.
5.3.4 Excessive temperatures
When operation of display devices is required in environments where temperatures are approaching
0 °C or  40 °C, users should take equipment and personal precautions to ensure that they are able to
complete their tasks satisfactorily and safely. Excessive temperatures will adversely affect the performance of
most display devices, as well as the associated electronic circuitry and therefore affect user performance on
the task. Consult the manufacturer's product specifications to find out the recommended operating range of
temperatures for the device. If the environmental conditions are close to or beyond the recommended limits,
the display device and the associated electronic circuitry may have to be heated or cooled to a temperature
level within the manufacturer’s specified range in order to ensure proper operation of the device(s).
5.4 Visual artefacts
5.4.1 General
Ideally, an electronic visual display will show only intended, high-quality information, in the form of text,
graphics or images. However, display technology is usually not ideal, and reflected images of the outside
world as well as unintended images due to visual perception phenomena cause visual artefacts,
i.e. information competing with the intended information for the viewer’s attention.
5.4.2 Luminance non-uniformity
For an intended uniform display luminance, the luminance non-uniformity, either step-wise or smooth, in
ambient illumination shall not exceed the threshold for reduced visual performance, with a maximum of 1,7:1.
5.4.3 Colour non-uniformity
Any non-uniformity of the colour shall not create competing information content when evaluated at three
locations on the screen. The maximum chromaticity difference shall be in accordance with Table 1.
6 © ISO 2011 – All rights reserved

ISO 9241-303:2011(E)
Table 1 — Maximum chromaticity difference
Chromaticity difference
D
(u,v)
active
D
design view Applications using colour
a
Any primary colour
per default colour set
 0,75 0,02 0,02
W 0,75 0,03 0,03
D diagonal of active area of screen
active
D design viewing distance
design view
a
The primary colours are the unmixed colours, usually red, green and blue.

Colour uniformity refers to how well the colour remains constant over the surface of the screen. Conversely,
non-uniformity of colour characterizes the manner in which the colour changes over the surface of the screen.
The non-uniformity of colours is best specified by the maximum colour difference (using some colour
difference metric) between any two points on the screen. Several colour different metrics and coordinates are
in use today, including CIELAB, CIELUV and CIE 1931 (x, y).
For the purposes of this part of ISO 9241, the metric, u,v colour difference, is used.
5.4.4 Contrast uniformity
Contrast uniformity can be important if proper recognition or presentation of information depends critically on
proper scene or pattern rendering. It is expressed as a percentage: contrast uniformity = 100 %(C /C ),
min max
where C and C are the minimum and maximum contrast, respectively, of the sampled contrast set on
min max
the screen (see ISO 9241-305). The contrast uniformity should be as high as possible and, in general, be
commensurate to the user’s task.
NOTE There are three different forms of contrast non-uniformity:
 variation in area average luminance contrast from the centre of a display to the edge of any portion thereof;
 variation of the peak contrast of character elements (dots or strokes) at different locations of the screen;
 variation of the peak contrast of character elements (dots or strokes) within a character.
The threshold for visual detection of contrast non-uniformity is higher than the threshold for measurable
difference in task performance. Both thresholds are dependent on the following factors:
 target size;
 contrast sensitivity of the user;
 task;
 luminance of the target, background and surrounds.
There are other ways of expressing contrast uniformity that may be found to be useful, for example, the ratio
of the “intended contrast”, such as that between text characters and their background, to the contrast that is
due to the contrast non-uniformity.
One way to ascertain the impact of contrast non-uniformity is to use a user performance test method (see
ISO 9241-304). Test persons representing a sample from the intended user population most likely to suffer
performance reduction should be used. In the test, the contrast uniformity shall be intentionally varied over the
screen.
ISO 9241-303:2011(E)
5.4.5 Geometric distortions
For different rows or columns of text, the difference of length shall not exceed 1 % of the length of that column
or row.
The horizontal displacement of a symbol position relative to the symbol positions directly above and below
shall not vary by more than 5 % of the character width. The vertical displacement of a symbol position, relative
to the symbol positions to the right and left of it, shall not vary by more than 5 % of the character height.
5.4.6 Screen and faceplate defects
The electronic display should be free of screen and faceplate defects.
1)
Regularly addressed dis
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