Information Graphics and Visuals
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Field of View A pair of healthy human eyes has a total field of view of approximately 200 degrees horizontally — about 120 degrees of which are shared by both eyes, giving rise to what's known as binocular vision — and 135 degrees vertically
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Locating your blind spot
Vanishing Head Illusion https://www.youtube.com/watch?v=O7jpJ12lBjg MA4847 Human Factor Engineering
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Types of visual acuity •Detection acuity: detection of presence of a target •Vernier or localisation acuity: detection of alignment, displacement •Resolution acuity: separation between discrete elements of a pattern (NVG resolution chart, Landolt/Cs) •Recognition acuity: naming of target (use Snellen text) •Dynamic acuity: detection & location of moving target
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Calculate readability of traffic sign Assume that the letters on a traffic sign are 0.2m. Calculate the maximum distance from which the driver can read, assuming the critical size of the sign is 30 arcmin. (1min of arc = 1/60 of a degree)
Tanθ = (A/2)/D Where A is the height of the character, D is the distance to the character from the eye, and 2 is the visual angle of the character. For small value of θ, tan θ= θ
Standard for minimum size of text on visual display
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Why signage fails We can learn a lot about creating successful sign layouts by considering what causes a sign to fail— 1. Too many signs in a concentrated area 2. Too much copy or wording 3. Poor design or layout 4. Bad choice of colors 5. Letter style that is not legible from the reading distance
Proposed Calculated Guide
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The Versatile Eye Rods contain rhodopsin which bleaches with light Cones contain 3 types of photopigments to enable colour vision. L-, M-, S-, maximum absorbtion respectively 565(yellow), 535 (green) & 430 (indigo) Rod: Cone ratio is 20:1 at 120:6 millions on retina
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The Versatile Eye •Colour processed automatically in parallel with size, shape, location & motion. Automatically processing of colour -> very useful means for redundant coding •7 to 10% males colour deficient •Colour stands out, facilitates vision search •Colour has semantics •Colour can convey relationships, e.g. grouping display •Colour increases useful field of view (UFOV) •Colour subject to limits of judgement _> use 5-6 colours •Colour may be distorted by ambient light, e.g sodium lamps •Colour does not convey an oderly order continum well. Use saturation, brightness and hue instead. •Automatic processing of colour-> irrelevant use can degrade user performance
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The Versatile Eye Colour subtraction (filter): mix before see, e.g. painting where blue + yellow = green Colour addition (overlay): vision through neural effects: see while mixing e.g RGB projector & TV, red + green = yellow
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The Versatile Eye Intensity: property of light energy Brightness: effect of intensity on observer Luminance (cd/m2 ) : emitted light from a source Illuminance (lux): light reflected off a surface Reflectance (%): property of a surface reflecting light Contrast: various definitions. Usually ratio of max & min luminances, or object & background luminances.
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The Versatile Eye Visual sensitivity increases with luminance; higher luminance-> greater depth of field as pupil diameter is smaller. User also subjected less to glare & need less contrast adaptation; but more susceptible to flicker, e.g. faulty fluorescent light /black text on white background is better only for newer monitors; (critical flicker/fusion frequency (CFF) & fatigue.)
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The Versatile Eye Scotopic vision: stimulus of 500nm first to be detected by this colourless system Photopic vision: chromatic or colour vision. Stimulus first to be detected is about 540nm (green colour)
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The Versatile Eye
Full dark adaptation takes about 45 minutes, much shorter for red light.
•Dark adaptation is enabled by both photochemical & neural processes: pooling of signals from rods connected serially •Visual/spatial resolution: ability to resolve or separate fine details. Ability of photopic vision>scotopic vision (10 times) •Visual sensitivity: ability to sense or detect dim stimulus (seeing stars at night). When dark adapted, ability of scotopic vision>photopic vision(can be 1000 times).
Dark adaption Curve for a 420nm Stimulus MA4847 Human Factor Engineering
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The Versatile Eye Temporal (Time related) resolution: photonic vision can distinguish stimuli separated by a brief instance of time, e.g. ability to see brief flashes of light Temporal summation: detection of position changes (motion) in a scenery when dark adapted. Why should recce bikers on the lookout at night rotate their heads gradually for better vision? Hint: distribution of rods over retina‌ Rods sum up visual information over space & time (spatial & temporal summation) due to configuration of connections
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Visual search Visual search most concentrated at central foveal regions of visual search Parallel & serial search affected by target salience (“jumping out� at you). Parallel search more effective-> increase discriminability of target to facilitate preattentive processing. Searching for presence of target feature different from absence of feature, eg search for Qs among Os is parallel search, serial search applies for reverse case. Search time requirements: scanning distance & visual clutter(density) trade off almost equally
Search time increase if more than one (different) target is required (e.g. quality inspection). Performance improves if the targets share a common feature distinct from distractors. Peripheral cues are proposed automatically (reaction to a surprise). Central cues require controlled interpretation. MA4847 Human Factor Engineering
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Voluntary Control of Vision: Determinants of Visual Sampling Behavior Mental model guides visual sampling: effect of expectancies & positive guidance (eg landmarks). Only first 50ms of a typical fixation of 200-600 ms duration is used for encoding information, remaining time used to plan the next fixation. Cognitive tunneling & bias affect visual sampling. Event rate affects visual sampling: more frequent sampling : more frequent visual sampling of high rate events & high information density. Bias disproportionate: moderated by cost-benefit assessment & other factors.
Display design & arrangement affect visual sampling: Can direct visual attention by appropriate design. Eg attentionattract by salient, unique singletons, colour, blinking, larger display features. Tendency towards horizontal & vertical scans rather than diagonal scans Preview helps optimisation of visual sampling, subject to limitation of working memory load Memory imperfect, visual sampling imperfect: out of sight, out of mind MA4847 Human Factor Engineering
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Directing Visual Attention Attention & depth: target at same depth processed faster. Noise & target at same depth degrades performance. Observation true unless target is very difficult to detect. If accurate cueing can be provided, attention can be directed. Otherwise avoid, as user tend to believe cueing & highlighting even when erroneous.
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Directing Visual Attention (Gastalt Principles) Proximity. The principle of proximity states that when an individual perceives an assortment of objects they perceive objects that are close to each other as forming a group.
Similarity. The principle of similarity states that elements within an assortment of objects are perceptually grouped together if they are similar to each other. This similarity can occur in the form of shape, colour, shading or other qualities.
Closure—The principle of closure states that individuals perceive objects such as shapes, letters, pictures, etc., as being whole when they are not complete. Specifically, when parts of a whole picture are missing, our perception fills in the visual gap.
Symmetry—The principle of symmetry states that the mind perceives objects as being symmetrical and forming around a center point. It is perceptually pleasing to divide objects into an even number of symmetrical parts. MA4847 Human Factor Engineering 19
Directing Visual Attention (Gastalt Principles) Common Fate—The principle of common fate states that objects are perceived as lines that move along the smoothest path.
Continuity—The principle of continuity states that elements of objects tend to be grouped together, and therefore integrated into perceptual wholes if they are aligned within an object.
Figure & Ground— The perception is used to describe the tendency of the visual system to simplify a scene into the main object that we are looking at (the figure) and everything else that forms the background (or ground)..
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Optical Illusion
https://www.youtube.com/watch?v=-IWk5NkxQF8
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Infographics
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Infographics
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Infographics
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Infographics
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Infographics Which one would you choose?
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A symbol is an object or a concept that represents, stands for or suggests another idea, visual image, belief, action or material entity.
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Visual aids such as graph and charts are used to represent/make sense of numbers
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http://www.visual-literacy.org/periodic_table/periodic_table.html MA4847 Human Factor Engineering
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End
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