ISO-9241-7-1998.pdf

AReference number ISO 9241-7:1998(E) INTERNATIONAL STANDARD ISO 9241-7 First edition 1998-04-01 Ergonomic requirements for office work with visual display terminals (VDTs) Part 7: Requirements for display with reflections Exigences ergonomiques pour travail de bureau avec terminaux à écrans de visualisation (TEV) Partie 7: Exigences d'affichage concernant les réflexions Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9241-7:1998(E) © ISO 1998 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 the publisher. International Organization for Standardization Case postale 56 CH-1211 Genève 20 Switzerland Internetcentraliso.ch X.400c=ch; a=400net; p=iso; o=isocs; s=central Printed in Switzerland ii ContentsPage 1 Scope1 2 Normative references1 3 Definitions and symbols .2 4 Guiding principles .7 5 Performance objectives 7 6 Requirements.7 7 Measurements and calculations 9 8 Compliance.16 Annex A: Alternative test method.18 Annex B: Graphical report format.22 Annex C: Worked example.26 Annex D: Bibliography.31 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- © ISOISO 9241-7:1998(E) iii 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. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 9241-7 was prepared by Technical Committee 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 3: Visual display requirements Part 4: Keyboard requirements Part 5: Workstation layout and postural requirements Part 6: Environmental requirements Part 7: Requirements for display with reflections Part 8: Requirements for displayed colours Part 9: Requirements for non-keyboard input devices Part 10: Dialogue principles Part 11: Guidance on usability Part 12: Presentation of information Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9241-7:1998(E) © ISO iv Part 13: User guidance Part 14: Menu dialogues Part 15: Command dialogues Part 16: Direct manipulation dialogues Part 17: Form-filling dialogues Annexes A, B, C and D of this part of ISO 9241 are for information only. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- © ISOISO 9241-7:1998(E) v Introduction Visual display terminals (VDTs) are subject to reflections of environmental luminance and illuminance from the display device surfaces. Under some conditions, the reflections become disturbing to the user and affect both comfort and task performance. The objective of this part of ISO 9241 is to maintain usable and acceptable VDT image quality in luminous environ- ments that can cause reflections from the screen. The document is intended for evaluators and users of VDTs. It is intended to be used with ISO 8995, ISO 9241-3, ISO 9241-6 and ISO 9241-8 to provide guidance for the visual ergonomics of the VDT workplace. Compliance with this part of ISO 9241 is dependent on the hardware characteristics of the VDT, except for polarity that can be application- dependent. This part of ISO 9241 contains requirements and methods for measurement of the image quality of VDTs used in luminous environments that can cause specular and diffuse reflections from the screen. ISO 9241-3 and ISO 9241-8 contain requirements that deal with luminance and luminance ratios for VDT images measured under conditions that exclude specular reflections. These parts of ISO 9241 interact with this part of ISO 9241. VDTs that meet the interacting requirements and recommendations of ISO 9241-3 and ISO 9241-8 do not necessarily meet those of this part ISO 9241 and vice versa. ISO 9241-6 and ISO 8995 contain specific recommendations concerning design of the workplace luminous environment to minimize sources of glare. The luminous environment conditions used to determine compliance with this part of ISO 9241 are drawn from, or are consistent with recommendations and requirements of these International Standards. The luminous environment values used to determine compliance to this part of ISO 9241 do not constitute specific recommendations or requirements for workplace lighting. The burden of a visually acceptable VDT workplace is a tradeoff between the display hardware and the VDT environment. To acknowledge that tradeoff, compliance with this part of ISO 9241 has been developed in three classes, each with rules for decision based on environmental assumptions. Although the decision rules are not expected to be exactly duplicated in the workplace environment, they do correspond approximately to general types of workplace environment to which VDTs are expected to be suitable: Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9241-7:1998(E) © ISO vi ClassEnvironment Isuitable for general office use IIsuitable for most, but not all, office environments IIIrequiring a specially controlled luminous environment for use An alternative test method is provided for VDTs whose characteristics preclude use of the quantitative test method. NOTE ISO 13406 extends the definitions, requirements, and test method of this part of ISO 9241 for flat panels whose colour and/or luminance contrast is strongly dependent on the direction from which they are viewed, and whose reflection characteristics can vary with the logical state of the screen. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD © ISOISO 9241-7:1998(E) 1 Ergonomic requirements for office work with visual display terminals (VDTs) Part 7: Requirements for display with reflections 1 Scope This part of ISO 9241 establishes image quality requirements for VDTs used in luminous environments that may cause reflections from the screen. The requirements are stated as performance or design specifications, and test methods are provided. applies to the ergonomic design of direct-view electronic displays for office tasks, including such activities as data entry, text processing and interactive inquiry. Office tasks are performed indoors, without exposure to direct sunlight. The recommendations can possibly be appropriate for other tasks, including process control, graphic design and computer-aided design, but their applicability has not been established. applies to monochrome and multicolour displays. The following displays and similar types are excluded from the scope of this part of ISO 9241: multi-user projection displays, transparent displays and virtual image displays. applies to VDTs for which its test method is suitable. The test method is limited to VDTs whose colour and/or luminance contrast does not vary strongly as a function of the viewing direction, and whose reflection properties do not vary as a function of the logical state of the screen. The test method is suitable for emissive VDT technologies, such as cathode ray tubes, and some flat panels. NOTE VDTs using display devices for which the test method of this part of ISO 9241 is not suitable (for example, liquid crystal displays) are directed to ISO 13406-2. 2 Normative references The following standards contain provisions which, through reference in the text, constitute provisions of this part of ISO 9241. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO 9241 are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 9241-3:1992. Ergonomic requirements for office work with visual display terminals (VDTs) Part 3: Visual dis- play requirements. ISO 9241-8:1997, Ergonomic requirements for office work with visual display terminals (VDTs) Part 8: Require- ments for displayed colours. CIE 17.4: 1989, International Lighting Vocabulary. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO 9241-7:1998(E) © ISO 2 3 Definitions and symbols 3.1 Definitions For purposes of this part of ISO 9241, the definitions given in ISO 9241-3 (except in 3.1.5) and the following definitions apply. 3.1.1 dark room: Room in which the only sources of light are the VDT under test and the prescribed sources of luminance or illuminance. 3.1.2 extended source of luminance: Area of uniform luminance, LA(EXT) with a width or diameter of at least 15° measured from the VDT screen centre. 3.1.3 luminance coefficient (at a surface element, in a given direction, under specified conditions of illumination)qV, q: Quotient of the luminance of the surface element in the given direction by the illuminance of the medium. see IEC (50) 845-04-71. NOTE It is expressed per steradian. 3.1.4 luminance factor (at a surface element of a non-self-radiating medium, in a given direction, under specified conditions of illumination)(bv, b): Ratio of the luminance of the surface element in the given direction to that of a perfect reflecting or transmitting diffuser identically illuminated based on IEC (50) 845-04-69 unit: 1 (unit: 1). 3.1.5 luminance ratio: Ratio between a higher and a lower area-average luminance, in which each luminance in the ratio is the sum of emitted and reflected luminance components, with one or more components common to both the numerator and the denominator. NOTE To reduce potential confusion, the terms contrast and luminance contrast are avoided in this part of ISO 9241. The luminance ratios of this part of ISO 9241 do not correspond to the luminance contrast within and between character details of ISO 9241-3. 3.1.6 negative polarity: Condition in which the foreground luminance LF is the highest luminance level of the display, and the background luminance, LB is the lowest luminance level of the display. 3.1.7 positive polarity: Condition in which the foreground luminance LF is the lowest luminance level of the display, and the background luminance, LB is the highest luminance level of the display. 3.1.8 reflectometer value: Value measured using the test method of this part of ISO 9241 for the diffuse luminance coefficient, RD (an estimate of q) and the specular reflection factor, RS (an estimate of b). NOTE The measured reflectometer value depends on the geometric characteristics of the test method, on the illuminant, on the spectral sensitivity of the detector (even when equipped with filters), and on the reference standard used. Adapted from CIE 50(845): 1987. 3.1.9 screen tilt angle, a a: Angle formed by the intersection of the plane tangent to the centre of the display and the horizontal plane. NOTES 1 This is identical to the angle A in 6.1.2 of ISO 9241-3:1992. 2 Figure 1 shows the intended angle. 3 Screen tilt angle is expressed in degrees. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 10:00:26 MDTNo reproduction or networking permitted without license from IHS -,-,- © ISOISO 9241-7:1998(E) 3 Key 1 Viewing side 2 Horizontal support surface Figure 1 Screen tilt angle 3.1.10 small source of luminance: Area with a diameter of 1° (measured from the screen) of uniform luminance (LA(SML), to be used in the measurement of specular reflections from screens with diffusing treatments. 3.2 Symbols 3.2.1 Primary symbols The primary symbols used in this part of ISO 9241 are shown below. See figure 2. Eilluminance, expressed in lux (lx) Lluminance, expressed in candela per square metre (cd/m 2) LRluminance ratio. (Unit: 1) RDreflectometer value for the diffuse reflection characteristic of the screen, obtained following the procedure below. It is the ratio of diffusely reflected luminance of the screen to its illuminance, under the conditions specified by clause 7 of this part of ISO 9241 (see 3.1.8). It is expressed per steradian (sr-1). The practical unit is candela per square metre per lux cd/(m 2 lx). RSreflectometer value for the specular and partially diffuse reflection characteristic of the screen, determined following the procedure of clause 7 of this part of ISO 9241. It is the ratio of specular and partially diffuse reflected luminance