Text Graphics Symbols and Codes Chapter 4 Text

Text, Graphics, Symbols, and Codes Chapter 4

Text, Graphics, Symbols, and Codes u Visual Capabilities u Hardcopy u VDT Screens u Graphic Representation u Symbols u Codes

Visual Capabilities u Accommodation u Visual Acuity u Contrast Sensitivity u Factors Affecting Visual Acuity and Contrast Sensitivity u Adaptation u Color Discrimination u Reading u Perception

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

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

Visual Capabilities u Contrast Sensitivity • Spatial frequency Fig 4 -2 4 -4 fig • Modulation contrast C= (Lmax－Lmin) / (Lmax＋Lmin) • Threshold contrast, Contrast sensitivity Fig 4 -5

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

Hardcopy u Criterion u Typography（印刷體裁）

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

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

Hardcopy－Typography u Stroke Width (stroke width – to – height ratio) Fig 4 -6 4 -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

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

Hardcopy－Typography u Size • Points: 1 -pt = 1/72 in (0. 35 mm) (p. 106) • For Close-up Reading u 一般: 9 – 11 pt u Luminance, Importance Tab 4 -2 • For Distance Reading u Subtend same visual angle u 公式 (p. 107) Tab 4 -3

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

Hardcopy－Typography u 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

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

VDT Screens u Screen Design Issues • Density u u 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

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

Graphic Representation u u 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↑

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

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

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

Codes Referents: the items to be coded Coding dimensions: types of visual sti. used u u u Single Coding Dimensions u Color 最佳 (? )　 Fig 4 -20 4 -21 Tab 4 -5 Color Coding (surface color) u Hue: 9 u Hue+Saturation+Brightness: 24 u Visual search 佳 u Meaning? Multidimensional Code Fig 4 -22