Ministry of Defence Defence Standard 00-25(Part 7)/Issue 2 20 December 1996 HUMAN FACTORS FOR DESIGNERS OF EQUIPMENT PART 7: VISUAL DISPLAYS This Part of Def Stan 00-25 Supersedes Def Stan 00-25 (Part 7)/Issue 1 Dated 27 October 1986 DEF STAN 00-25 (Part 7)/Issue 2 AMENDMENTS ISSUED SINCE PUBLICATION AMD NO DATE OF TEXT AFFECTED SIGNATURE & ISSUE DATE Revision Note This Defence Standard has been revised to promote its status from an Interim to a full Defence Standard; also to provide up-to-date technical advice, guidance and data which reflects recent advances in the subject including helmet mounted sighting systems. Historical Record This Defence Standard has its origins in “Human Factors for Designers of Naval Equipment” (a naval handbook in two volumes) published in 1971. Arrangement of Defence Standard 00-25 The arrangement of the Parts comprising Def Stan 00-25 is shown below. PART 1 - Introduction PART 2 - Body Size PART 3 - Body Strength and Stamina PART 4 - Design of Workspace PART 5 - The Physical Environment: Stresses and Hazards PART 6 - Vision and Lighting PART 7 - Visual Displays PART 8 - Auditory Information PART 9 - Voice Communication PART 10 - Controls PART 11 - Design for Maintainability PART 12 - Systems PART 13 - Human Computer Interaction PART 14 - Training and Instruction (not yet published) Two or more Parts may apply to any one equipment and it is, therefore, essential that all Parts be read and used where appropriate. DEF STAN 00-25(PART 7)/2 HUMAN FACTORS FOR DESIGNERS OF EQUIPMENT PART 7: VISUAL DISPLAYS PREFACE This Part of Def Stan 00-25 supersedes Def Stan 00-25 (Part 7)/Issue 1 Dated 27 October 1986 i This Part of the Defence Standard presents descriptive detail, technical data and diagrams relating to some of the important factors concerned with visibility comprehension and presentation of Visual Displays. ii This Part of the Defence Standard is published under the authority of the Human Factors Subcommittee of the Defence Engineering and Equipment Standardization Committee (DEESC). iii This Standard should be viewed as a permissive guideline, rather than as a mandatory piece of technological law. Where safety and health is concerned, particular attention is drawn to this Standard as a source of advice on safe working limits, stresses and hazards etc. Use of this Standard in no way absolves either the supplier or the user from statutory obligations relating to health and safety at any stage of manufacture or use. iv Users of this Standard shall note that some material may be claimed to be subject to copyright in this or other countries. Copyright where known is acknowledged. v This Standard has been devised for the use of the Crown and its contractors in the execution of contracts for the Crown. The Crown hereby excludes all liability (other than liability for death or personal injury) whatsoever and howsoever arising (including, but without limitation, negligence on the part of the Crown its servants or agents) for any loss or damage however caused where the Standard is used for any other purpose. vi This Standard has been agreed by the authorities concerned with its use and is intended to be used whenever relevant in all future designs, contracts, orders etc and whenever practicable by amendment to those already in existence. If any difficulty arises which prevents application of the Defence Standard, the Directorate of Standardization shall be informed so that a remedy may be sought. vii Any enquiries regarding this Standard in relation to an invitation to tender or a contract in which it is incorporated are to be addressed to the responsible technical or supervising authority named in the invitation to tender or contract. 1 DEF STAN 00-25(PART 7)/2 CONTENTS PAGE Preface 1 Section One. General 0 Introduction 4 1 Scope 4 2 Related Documents 5 3 Definitions 6 Section Two. Pratical Techniques for Display Specification 4 Task Requirements 13 5 Context of Use 13 6 Identifying Users and User Requirements 17 7 Modelling User Tasks 19 8 Providing User Support and Training for the Display 22 Section Three. Perception of Information from Displays 9 Quantitative Displays 24 10 Qualitative Displays 27 11 Coding 38 12 Symbols 41 13 Use of Text 45 14 Display Integration and Grouping 49 Section Four. Physical Characteristics of Display 15 Viewing Position 55 16 Size of Displayed Information 58 17 Contrast 61 18 Displayed Colour 64 19 Electronic Displayed Characteristics 64 Table 1 Examples of Visual Perceptual Characteristics from Target Audience Descriptions to be Taken into Consideration in Display Design 18 Table 2 Recommended Sizes of Scale Markers 26 Table 3 Common Associations for Colours 40 Table 4 Character Size and Viewing Distance 59 Table 5 Character Size and Luminance 59 Figure 1 Task Description of a Hypothetical Missile System Using HTA 20 Figure 2 Control Loop Between Operator and Display 21 Figure 3 Types of Mechanical Dynamic Quantitative Display 24 Figure 4 Recommended Sizes of Scale Markers 26 Figure 5 Methods of Adding Qualitative Coding to Quantitative Displays 29 Figure 6 Examples of Display Grouping using Human Factors Principles of Proximity and Similarity 50 Figure 7 Examples of Display Arrangement Using Human Factors Principles of Continuation and Closure to Facilitate Check Reading 51 2 DEF STAN 00-25 (PART 7)/2 CONTENTS PAGE Figure 8 Optimum and Maximum Positions for Displays in the Visual Field, Allowing for Eye Movement, Head Movement and Eye and Head Movement (LOS = Line of Sight) 56 Figure 9 Height of FPD Characters 60 Annex A Related Documents A-1 3 DEF STAN 00-25 (PART 7)/2 HUMAN FACTORS FOR DESIGNERS OF EQUIPMENT VISUAL DISPLAYS Section One. General 0 Introduction 0.1 The aim of this Part of the Standard is to help designers produce effective visual displays by providing guidance on characteristics of the human visual system and physical design that influence perceptual performance. This aim is supported by offering the designer practical techniques for establishing design criteria during the early stages of the design. 0.2 The design principles are intended to be sufficiently generic to be applicable to most display types, from hand-produced signs to three- dimensional interfaces. The general guidance is supported by technology- specific recommendations, where appropriate. certain clauses may not be applicable or relevant for particular display media or operational tasks. Consequently, the designer should always adhere to the general principles and ethos of the Standard ahead of the specific detail. For these reasons it will be necessary for the designer to consult other sources of information for guidance on specific technologies and topics, such as Head- Up Display optics or strategic symbols used in active radar. Annex A provides a list of related documents. 1 Scope 1.1 The principles described in this Part of the Standard have been designed to be applicable to the vast majority of displays used for military purposes, irrespective of display technology, as far as is realistic given the rapid advance of display technology. Consequently, the emphasis of this Part of the Standard is on providing guidance rather than limited prescriptive specification. Nonetheless, principles expressed usinq the term ‘should’ have the strongest emphasis and the designer ought to be clear in his/her justification for departures from such recommendations. 1.2 This Part of the Standard is divided into four Sections, a General introduction, followed by three Sections reflecting conceptual stages in a design process to produce effective displays. 4 DEF STAN 00-25 (PART 7)/2 1.2 (Contd) General Section One: General introduction including combined definition First decide who the and glossary of terms used in design is for, how it sections two to four. will be used and in what circumstances Section Two: helps the designer Practical Techniques establish design criteria based on for the context in which the display is Display Specification to be used, including the physical and operational environments, and Next, consider how to relevant characteristics of the portray the meaning of operators. the information clearly and efficiently Section Three. provides guidance on designing displays to meet human perceptual capabilities and Perception of Information limitations. from Displays Section Four: provides guidance Then consider how it on the physical characteristics of can be achieved, given displays that influence human the possibilities and performance. Physical Characteristics constraints of the of Displays display media 2 Related Documents 2.1 Related documents can be obtained from: DOCUMENT SOURCE British Standards (BS) (BSEN) BSI (IEC) and ISO Sales Office Linford Wood MILTON KEYNES MK14 6LE North Atlantic Treaty NMST Organization (NATO) Room 202 Standardization Agreement Archway Block (South) (STANAG) Old Admiralty Building (NATO Publication APP6) Spring Gardens LONDON SW1A 2BE 5 DEF STAN 00-25 (PART 7)/2 2.1 (Contd) DOCUMENT SOURCE Health and Safety at Work HMSO Regulations South Gyle Crescent MOD MANPRINT Handbook EDINBURGH EH12 9EB PULHHEEM’s Administrative Pamphlet Defence Standards Directorate of Standardization (Stan 1) Kentigern House 65 Brown Street GLASGOW G2 8EX 2.2 Reference in this Standard to any related documents means in any invitation to tender or contract the edition and all amendments current at the date of such tender or contract unless a specific edition is indicated. 2.3 The documents referred to in this Part of the Standard, together with additional publications providing greater coverage on specific aspects of the subject, are listed at annex A. 3 Definitions For the purpose of this Part of the Standard the definitions described below apply. Achromatic (displays): Displays generating colours that are perceived to be without hue. The colour names grey, black and white are commonly used. Adaptation: The process that takes place as the visual system adjusts itself to the brightness or the colour (chromatic adaptation) of the visual field. The term is also used, usually qualified, to denote the final state of this process. For example ‘dark adaptation’ denotes the state of the visual system when it has become adapted to a very low luminance. Advisors: A type of status indicator used to inform the operator of a condition or state that requires general awareness of a marginal or predicted imminent condition. Alarm: A type of status indicator used to inform the operator of a hazardous condition or state. Ambient illumination: General level of illumination at the workstation. Anisotropic (display surface): A display surface for which radiation deviates from that of a Lambertian surface (see IEC 845-04-57) by more than 10% at any inclination angle 0 < 45°. 6 DEF STAN 00-25 (PART 7)/2 3 (Contd) Anthropometry: The measurement of human body dimensions. See Def Stan 00-25 (Part 2). Attenson: A sound used to or inform. Auditory cue: A sound designed to prompt the operator for a specific action. BARB: British Army Recruitment Battery pre-selection test. Brightness: The subjective response to luminance in the field of view dependent upon the adaptation of the eye. Candela (cd): The SI unit of luminous intensity, equal to one lumen per steradian. Caution: A type of status indictor used to inform the operator of a condition or state that requires immediate attention and a rapid remedial action. See also Advisors; Warnings. CLOS (operation): A type of tracking system, ‘command-to-line of sight’, in which the controlled device (eg missile path) follows the operator’s command. Code (visual): A systematic technique for representing information used aid comprehension. Codes can be used to speed interpretation, or to make presentation of the information more efficient (eg by reducing the size). Codes can also be used to add to, or modify the meaning of the information. Contrast: (see also Def Stan 00-25 (Part 6)) A term that is used subjectively and objectively. Subjectively it describes the difference in appearance of two parts of a visual field seen simultaneously or successively. The difference may be one of brightness or colour or both. Objectively, the term expresses the luminance difference between the two parts of the field by such relationships as the difference between the luminance of the target and background, eg expressed as a ratio: L Contrast Ratio, C = max R L min Where L and L luminance represent the maximum and minimum luminance in max min cd/m2, respectively - ie the luminance of the target and background. Contrast sensitivity: The ability to perceive a lightness or brightness difference between two areas. See also Def Stan 00-25 (Part 6). Control display dynamics: The spatial relationship between the control input and the display output. CRT: Cathode ray tube. 7 DEF STAN 00-25 (PART 7)/2 3 ( Contd ) ‘Dark quiet’ (design philosophy): Status indicator design philosophy in which the displayed information is not visible or audible until directly relevant. Descenders (in text): Elements of lowercase letters that extend below the baseline, eg on the letters g, p, j, y. Diacritic: A modifying mark near or through a letter indicating a phonetic value different from that given the unmarked letter, eg a cedilla in ‘façade’. Diffuse reflection: Reflection in which the reflected light is diffused and there is no significant specular reflection, as from a matt paint. Direct lighting: Lighting in which the greater part of the luminous flux from the luminaires reaches the surface (usually the working plane) directly, ie without reflection from surrounding surfaces. Luminaires with a flux fraction ratio less than 0.1 are usually regarded as direct. Disability glare: Glare produced directly or by reflection that impairs the vision of objects without necessarily causing discomfort. Discomfort glare: Glare which causes visual discomfort. Display (visual): The type of information medium that is relevant to, and observed by, the human sense of sight. Display modality: The human perceptual sense through which the display stimulus is perceived, eg visual, auditory, tactile, olfactory. Dot matrix: A system of displaying characters within a given matrix of dots , often 7 x 9 or 5 x 7. Duty cycle: The ratio of the active display interval compared versus the flashing interval, of a flashing stimulus, expressed as a percentage. See also Flash Coding. Effective reflectance: Estimated reflectance of a surface, based on the relative areas and the reflectance of the materials forming the surface. Thus ,‘effective wall reflectance’ takes account of the reflectance of the wall surface, the windows, the filing cabinets etc, that comprise the sides of the room. Emissive (displays): Displays that contain their own light source(s). The light is either produced by the transducer itself or provided by one or more internal light sources modulated by the transducer. Flash coding: Information presented by temporal luminance variations, sometimes referred to as blink coding. See also Duty Cycle. Flat panel displays (FPDs): Various types of electronic displays presenting information on a thin panel, eg Liquid Crystal Display (LCD), Electroluminescent Display (ELD), Gas Plasma Display (GPD), Vacuum Fluorescent Display (VFD). 8