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Text, Graphics, Symbols, and Codes

Text, Graphics, Symbols, and Codes. Chapter 4. Text, Graphics, Symbols, and Codes. Visual Capabilities  Hardcopy  VDT Screens  Graphic Representation  Symbols  Codes . Visual Capabilities. Accommodation Visual Acuity Contrast Sensitivity

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Text, Graphics, Symbols, and Codes

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  1. Text, Graphics,Symbols, and Codes Chapter 4

  2. Text, Graphics,Symbols, and Codes • Visual Capabilities  • Hardcopy  • VDT Screens  • Graphic Representation  • Symbols  • Codes 

  3. Visual Capabilities • Accommodation • Visual Acuity • Contrast Sensitivity • Factors Affecting Visual Acuity and Contrast Sensitivity • Adaptation • Color Discrimination • Reading • Perception

  4. Visual Capabilities • Accommodation • Near point, Far point • Diopters (D)=1/distance(m) • Dark focus: about at arm’s length (1m or 1D)

  5. Visual Capabilities • Visual Acuity: Discriminate fine detail • Minimum separable acuity Fig 4-2 • Visual angle (VA): VA (minutes) = 3438×H/D; Fig 4-3 • Acuity = 1 / VA (min) • Other types of acuity: • Vernier acuity • Minimum perceptible acuity: detect dot from background • Stereoscopic acuity

  6. Visual Capabilities • Contrast Sensitivity • Spatial frequency Fig 4-24-4 fig • Modulation contrast C= (Lmax－Lmin) / (Lmax＋Lmin) • Threshold contrast, Contrast sensitivity Fig 4-5

  7. Visual Capabilities • Factors Affecting Visual Acuity and Contrast Sensitivity • Luminance level: cone vs. rod • Contrast: contrast acuity • Modulation contrast • Luminous contrast = (Lmax－Lmin) / Lmax • Contrast (or luminance) ratio = Lmax / Lmin • Exposure time: improve up to 100-200ms • Target motion: dynamic visual acuity • Age • Training

  8. Hardcopy • Criterion • Typography（印刷體裁）

  9. Hardcopy－Criterion • Visibility • Legibility：易識別 Discriminability • Readability： Recognition of the information content of material (meaningful groupings: words, sentences, text…)

  10. Hardcopy－Typography 何時需設計較佳的 Typography： • Viewing Conditions：unfavorable • Information：important critical • Distant Viewing • Poor Vision (People)

  11. Hardcopy－Typography • Stroke Width (stroke width – to – height ratio) Fig 4-64-7 • Normal: 白底黑字1:6 – 1:8 黑底白字1:8 – 1:10 • Illumination: low→ thick • Contrast: low→ thick • Highly luminous letter: thin 1:12 – 1:20 • 黑字on 亮背景: very thick

  12. Hardcopy－Typography • Width-to-Height Ratio Fig 4-8 • Styles of Type Tab 4-1 • 一般: Roman • 斜體 (Italics): 特殊用法 or 重要者 • 粗體 (Bold): 重點

  13. Hardcopy－Typography • Size • Points: 1-pt = 1/72in (0.35mm) (p.106) • For Close-up Reading • 一般: 9 – 11 pt • Luminance, Importance Tab 4-2 • For Distance Reading • Subtend same visual angle • 公式 (p.107) Tab 4-3

  14. Hardcopy－Typography • Case • 小寫: 易讀 (因 envelop, e.g. pie, big, pig) • Search for particular label • “開頭字母”重要，宜特大 • (e.g.) Case vs. Case; CASE vs. CASE • Layout Fig 4-9 • Interletter spacing（字距） • Interline spacing（行距）

  15. Hardcopy－Typography • Reading Ease • Type of Sentence（句型） Simple, Affirmative, Active • Order of Words Match the order of action • Index of Readability Tab 4-4 Score = 206.835－(0.846× S) －(1.015× W) S: syllables of 100 words W: no. of words per sentence

  16. VDT Screens • 基本性質 • Typography • Reading Distance • 20 in (45cm) • Eye-to-screen=Eye-to-keyboard (Accommodation) • Size • Hardware Considerations • Polarity • Color • Screen Design Issues

  17. VDT Screens • Screen Design Issues • Density Fig 4-11 • Global density: mean=25% (600 data screens) • Local density the no. of filled character spaces near other characters • Density↑→ Performance↓ • Reduce density: Abbreviation, Avoid unnecessary information, Concise wording（簡潔）, Tabular format

  18. VDT Screens • Grouping • Size of the groups＜ 5º (VA): No. 愈少愈好 • Size of the groups＞5º：Size 愈小愈好 • Complexity • Tullis (1983) Arrangement (layout) complexity: The extent of arrangement follows a predictable visual scheme • Columnar arrangement Fig 4-12 • Highlighting / Blinking (end)

  19. Graphic Representation • Of Text • 不受限於語言 • Instruction, Procedure manual • Combine Pictorial & text Pictorial: speed; Text: accuracy • Of Data • Pie chart, Bar chart, Line chart • 2-D, 3-D Fig 4-13 • Distortion: Fig 4-14 • Guideline: correct perception↑

  20. Symbols • Symbolic vs. Verbal Signs Fig 4-15 • Objectives of Symbolic Coding Systems • Best Represent their Referent: depend on strength of association of a symbol with its referent • Guideline: Detectability, Discriminability, Compatibility, Meaningfulness, Standardization • Criteria for Selecting Coding Symbols • Recognition • Matching • Preference & Opinions

  21. Symbols • Example of Studies • Mandatory-Action Symbols Fig 4-16 • Original test, Second test • Recognition 佳 • Subjects:初臨澳洲的越南人 (different culture) • Exit Symbols Fig 4-17 • Filled • Background: 方＞圓 • Simplified figure

  22. Symbols • Perceptual Principles Fig 4-18 • Figure/Ground • Figure boundary • Closure • Simplicity • Unity • Standardization • International road signs Fig 4-19 (end)

  23. Codes Referents: the items to be coded Coding dimensions: types of visual sti. used • Single Coding Dimensions • Color 最佳 (?)Fig 4-204-21Tab 4-5 • Color Coding (surface color) • Hue: 9 • Hue+Saturation+Brightness: 24 • Visual search 佳 • Meaning? • Multidimensional Code Fig 4-22

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