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					              Light and Sound,
            Seeing and Listening

2.1 Perception
2.2 Light
2.3 Color and Color Sensation
2.4 Sight and Visual Communication
2.5 Sound
2.6 Listening and Auditory Communication

Chapter 2              Theoretical Foundations of Multimedia
       Perception and Cognition


Perception — the consciousness or
 awareness of objects or other data
 through the medium of the senses.

Cognition — high-order mental processes,
 such as complex representation,
 inference, and interpretation, that lead to
 perception and then to understanding.

Chapter 2               Theoretical Foundations of Multimedia
             “Regions of Interest”
            for Studying Perception

•   The Environment
•   Incoming stimuli
•   Sensory surfaces and peripheral neurons
•   The Brain
•   Effector systems
•   Motor responses

Chapter 2               Theoretical Foundations of Multimedia
            Optical Illusions




Subjective contours      Archimedes spiral



             Müller-Lyer Illusion
Chapter 2               Theoretical Foundations of Multimedia
            Auditory Illusions


 • Bach sonatas and partitas
 • Ravel’s Bolero




Chapter 2              Theoretical Foundations of Multimedia
            The Nature of Light


•   A form of energy
•   Particle nature of light
•   Waveform nature of light
•   Early Philosophers and Researchers:
        Plato                  Sir Isaac Newton
        Alhazen                Thomas Young
        Christopher Scheiner   Max Planck

Chapter 2                  Theoretical Foundations of Multimedia
            The Behavior of Waves




                   A Sine Wave

Chapter 2                Theoretical Foundations of Multimedia
            The Behavior of Waves




                 1 sec.   2 sec.         3 sec.



    One cycle per second, or 1 hertz (Hz)


Chapter 2                  Theoretical Foundations of Multimedia
            The Behavior of Waves




       Two waves of equal frequency and
             different amplitudes
Chapter 2               Theoretical Foundations of Multimedia
            The Behavior of Waves




       Two waves and the wave resulting
             from their interaction
Chapter 2                Theoretical Foundations of Multimedia
            The Behavior of Waves




       Two equivalent waves in phase
               cancellation
Chapter 2                Theoretical Foundations of Multimedia
            The Behavior of Waves




       Two equivalent waves in phase
           and the resultant wave
Chapter 2                Theoretical Foundations of Multimedia
            The Behavior of Waves



  A fundamental
  waveform and
  its second and
  third harmonics




Chapter 2              Theoretical Foundations of Multimedia
            The Elecromagnetic
                 Spectrum




Chapter 2             Theoretical Foundations of Multimedia
            The Elecromagnetic
                 Spectrum




Chapter 2             Theoretical Foundations of Multimedia
            The Speed of Light


    • 186,282.3959 miles per second
    • Events within sight appear to be
         instantaneous
    • Speed varies in different media
    • Some materials absorb some of
         the light’s energy


Chapter 2                Theoretical Foundations of Multimedia
            The Measurement of
                  Light
  • Intensity or “strength” of radiation
  • Radiance — the total amount of energy
        (light and heat) measured in watts
  • Luminance — light strength perceived
        by a human eye
  • Brightness — subjective measure of how
        bright an object appears to a human
  • Strength diminishes by inverse square
        proportion to distance from source
Chapter 2              Theoretical Foundations of Multimedia
                 Reflection

  Reflection — light strikes a surface and
    the waves bounce off
    • May cause problems on a monitor
       under the wrong lighting conditions
      • Allows fiber optic cables to function
         by causing the light being sent
         along the fiber to “bounce” off of
         the walls of the cable and continue
         toward the other end
Chapter 2                  Theoretical Foundations of Multimedia
              Refraction

  Refraction — light passes
    through a different
    medium and has its
    direction changed;
    sometimes called the
    “bending” of light




Chapter 2              Theoretical Foundations of Multimedia
                 Refraction

       Prism separating white light




Chapter 2                 Theoretical Foundations of Multimedia
                 Refraction

       Lenses focus or spread light




Chapter 2                 Theoretical Foundations of Multimedia
                    Color


      The sensation registered in the brain
      when different wavelengths of light
      impinge upon the retina of the eye,
      causing a message to be sent along
      the optic nerve to excite neurons in
      various portions of the brain.


Chapter 2                 Theoretical Foundations of Multimedia
                    Color

      Reflected color occurs when a light
      illuminates an object and some of the
      wavelengths of the light are reflected
      off of the object, while others are
      absorbed by it.

      Transmitted or emitted color results
      from an atom or a molecule emitting
      light energy of a characteristic wave-
      length after being excited.
Chapter 2                 Theoretical Foundations of Multimedia
               Measuring Color




            Emission and Remission Curves

Chapter 2                  Theoretical Foundations of Multimedia
            Measuring Color

• Chroma — hue, or a color’s pure
     expression
• Saturation — the amount of pure color
     (not black or white) in a chroma
• Value — subtle difference between
  shades and tints
• Lightness — amount of light reflected
     from an object
• Brightness — luminance of an object in
  the context of its surroundings
Chapter 2             Theoretical Foundations of Multimedia
            Trichromatic Vision

• Subtractive principle of color — reflected
  color
• Additive principle of color — emitted
  color
• Thomas Young — proposed that the eye
  is composed of three different light-
  sensitive materials
• Hermann von Helmholtz — identified the
  retinal cells for the three colors
• Young-Helmholtz Theory — three–
  component or trichromatic vision theory
Chapter 2              Theoretical Foundations of Multimedia
            Perception of Color

• The eye sees different wavelengths and
  intensities very differently
• Violet is barely perceived
• Red is seen very well
• The cornea is yellow, and absorbs green,
  blue, and Violet
• As people age, the cornea becomes even
  more yellow so they see even less green,
  blue, and Violet
Chapter 2             Theoretical Foundations of Multimedia
       Psychological Aspects of
               Color
• Descriptive phrases — seeing Red; feeling
  blue; a black mood; a yellow coward
• Color is highly subjective
• Colors are associated with emotions
• Warm colors (Red and yellow) appear near
• Cool colors (blue and green) appear more
  distant
• Pastels appear relaxed; dark colors seem
  more angry
Chapter 2              Theoretical Foundations of Multimedia
            Color Wheel

                    blue
            cyan
                               magenta




                             red

            green
                    yellow


Chapter 2           Theoretical Foundations of Multimedia
            Colors on Computer
                 Monitors
• Radiated vs. reflected light (recall the
     additive principle vs. the subtractive
     principle of light)
• RGB system — Red, green, blue
• CYM system — Cyan, yellow, magenta
• HSV system — hue, saturation, & value
• HLS system — hue, lightness, & saturation
• CIE system — Commission Internationale
     de l’Eclairage
Chapter 2              Theoretical Foundations of Multimedia
                    RGB Color Cube

              B       cyan
                                                          white

                             magenta
       blue
                                          gray line



                                G

                                                          yellow
                       green

                                                      R
            black                   red

Chapter 2                           Theoretical Foundations of Multimedia
            Sight and Visual
            Communication
• Physical process — light being trans-
    mitted and reflected
• Physiological process — light enters the
    eye, falls on the retina, and is trans-
    mitted by the optic nerve
• Neurological process — the brain reacts
    to the impulses from the optic nerve
• Psychological process — the mind
    interprets the information in the brain
Chapter 2               Theoretical Foundations of Multimedia
            Sight and Visual
            Communication

            The Camera Obscura




Chapter 2             Theoretical Foundations of Multimedia
            Sight and Visual
            Communication

                                 Comparing
                                 a camera
                                 and the
                                 human eye




Chapter 2            Theoretical Foundations of Multimedia
      Aspects of Visual Literacy

• A prerequisite for the comprehension of
  visual media

• General cognitive consequences

• Awareness of visual manipulation

• Aesthetic appreciation

Chapter 2                  Theoretical Foundations of Multimedia
            Images and Meaning

• Sense — the external reality denoted by
     an image
• Feeling — the attitude conveyed by an
     image regarding the expressed reality
• Tone — the attitude or message that the
     creator of an image wishes to transmit
• Intention — the effect that an image is
     desired to produce in a viewer

Chapter 2               Theoretical Foundations of Multimedia
            Images and Meaning

• Sign — any physical object to which a
     community ascribes meaning
• Semiotics or Semiology — study of signs
• Signifier — the physical entity that
     expresses the sign
• Signified — the concept or emotion that is
     conveyed by the sign
• Signification — the link between the
     expression and the concept
Chapter 2               Theoretical Foundations of Multimedia
            Images and Meaning

To refute the assertion that pictures are arbitrary in their
connection to what they purport to represent, Messaris
uses the real-life situation of the powerful and powerless
camera angles




Chapter 2                        Theoretical Foundations of Multimedia
  Lester’s pragmatic perspectives for
   analyzing and interpreting images

• Personal — gut reaction; subjective
• Historical— importance of the image based on
      the medium’s time line
• Technical — relationship between light, the
      recording medium, and the presentation
• Ethical — producer’s, subject’s, and viewer’s
      moral and ethical responsibilities to the work
• Cultural — analysis of the work’s symbols that
      convey meaning in this society at this time
• Critical — issues transcending a particular
      image to shape a reasoned reaction
Chapter 2                   Theoretical Foundations of Multimedia
               Still Images




        Concrete          Abstract
Chapter 2             Theoretical Foundations of Multimedia
      Messaris’ ten major discrepancies
     between concrete images and reality

• Cannot reproduce full range of brightness
• Cannot reproduce full range of colors
• Lack information about changes in brightness
• Lack information about the color of objects
• Cannot reproduce a stereoscopic effect
• Cannot reproduce motion parallax effects
• May not show diminution of size with increasing
  distance from the viewer
• May not be constrained to a single view at a time
• May contain major distortions of features
• May entail omissions of features of the subject
    Chapter 2              Theoretical Foundations of Multimedia
   Messaris’ ten major discrepancies
  between concrete images and reality
Messaris’ discrepancies do not present a serious problem.
  Human beings, even from a very young age, show a
  remarkable capacity to recognize and correctly identify
  even the most stylized or incomplete concrete
  representations, regardless of the presence or absence
  of color, depth cues, or a preponderance of easily
  recognizable objects.

The significance of this observation for a multimedia
  developer is that the expense of creating and displaying
  extremely high-resolution, realistic graphics generally is
  not necessary. The lesson is not to waste resources on
  glitz but to devote them to substance.
Chapter 2                        Theoretical Foundations of Multimedia
             Components of Form

• Dot — a small circle that has been filled in
• Line — a sequence of dots so close together that
  there appears to be no space between them
• Shapes
    Parallelogram — a four-sided figure with
    opposite sides parallel and equal in length
    Circle — the locus of all points equidistant
    from a given point
    Triangle — a three-sided figure
      – equilateral
      – isosceles
Chapter 2                  Theoretical Foundations of Multimedia
            Arrangements of Dots




    Center of    Tension     Tension               Fill in
    attention    through     through             the dots
                asymmetry    division



Chapter 2                   Theoretical Foundations of Multimedia
            Arrangements of Lines




      Open      Constricted     Vertical        Dynamism
      space       space           halt              and
                                                 direction



Chapter 2                     Theoretical Foundations of Multimedia
            Arrangements of Lines
                 (continued)




    Nervous      Strength    Grace and           Parallel
     energy        and        airiness            lines
                confidence                       and text



Chapter 2                    Theoretical Foundations of Multimedia
            Uses of Shapes —
             Parallelograms




      Unbalanced   Balanced use of white space
      appearance

Chapter 2               Theoretical Foundations of Multimedia
             Uses of Shapes —
                  Circles




     This circle dominates      This circular device is an
        the field it is on.   immediate attention-grabber

Chapter 2                       Theoretical Foundations of Multimedia
            Uses of Shapes —
                Triangles




     Pyramid —     Isosceles triangle Isosceles triangle
     symbol of         pointing up         strongly
    strength and    evokes image of       indicates
       stability    a church steeple      direction
Chapter 2                     Theoretical Foundations of Multimedia
            Graphics Primitives

• Point — a pixel on a computer screen

• Line — two or more pixels connected
  (adjacent) to each other

• Polygon — a closed figure of more than
  two sides existing in one plane

• The computer domain of straight lines and
  geometrical figures cannot reproduce
  perfect renditions of the real world
Chapter 2              Theoretical Foundations of Multimedia
  Factors Providing a Sense of Depth

• Space — the frame in which an image is set
• Size — apparent sizes of objects provide clues
• Color — warm colored objects seem closer than
  cool ones, as do more highly contrasted objects
• Lighting — differences in light intensity and
  shadowing portray depth
• Textural Gradients — e.g., ripple effects become
  closer together in the distance
• Time — a culture’s perception of time influences
  the depiction of depth
• Perspective — a drawing technique
Chapter 2                  Theoretical Foundations of Multimedia
     Three forms of Perspective




    Illusionary   Geometrical          Conceptual
    perspective   perspective          perspective



Chapter 2                Theoretical Foundations of Multimedia
            Motion in Images

• Real movement — animate and inanimate
  objects in motion in the real world
• Apparent movement —still images
  providing the appearance of motion
• Persistence of vision — the retention of an
  image in the brain for a period of time
• In MM, the number of images per second
  and the viewer’s persistence of vision de-
  termine the appearance of realistic motion
Chapter 2               Theoretical Foundations of Multimedia
                Motion in Images

• Albert Michotte — Perception of physical
  causality
      launching effect
      entraining effect

• Graphic movement —the motion of the
  eyes in scanning an object (often left-to-
  right, top-to-bottom); culturally based
• Implied movement — the illusion of motion
  in a still image, without any movement of
  the image, its surroundings, or the viewer
Chapter 2                  Theoretical Foundations of Multimedia
                   Early Writing




            Ideographs          Pictographs

Chapter 2                 Theoretical Foundations of Multimedia
                       Early Writing




            Hieroglyphics                 Logograms




       Early Alphabets                     Cuneiform
Chapter 2                     Theoretical Foundations of Multimedia
                      Typography


 Movable
 Type

 A page
 from a
 Gutenberg
 Bible


Courtesy of special
collections, M. I.
King Library, Uni-
versity of Kentucky

Chapter 2                   Theoretical Foundations of Multimedia
Typography

       Movable
       Type

       Same page
       from a
       Gutenberg
       Bible showing
       colored inks
       and illuminations


       Courtesy of special
       collections, M. I.
       King Library, Uni-
       versity of Kentucky

Chapter 2                    Theoretical Foundations of Multimedia
                Typefaces —
               Serif Typefaces
                AGaramond
                   Palatino
            Bookman Old Style
                  Courier
              Footlight MT Light
                 New York
Chapter 2              Theoretical Foundations of Multimedia
               Typefaces —
            Sans Serif Typefaces
                  Arial
               Arial Narrow
             Century Gothic
                Chicago
               Helvetica
                 Impact
Chapter 2              Theoretical Foundations of Multimedia
              Typefaces —
            Special Typefaces
              Braggadocio
              Brush Script MT
               Desdemona
                   Mistral
                Stencil
                 Symbol
                   (symbol)
Chapter 2                 Theoretical Foundations of Multimedia
            Typefaces —
            Type Styles
              Bold
              Italic
             Outline
            Underline
             Shadow
            SMALL CAPS
Chapter 2         Theoretical Foundations of Multimedia
               Typefaces —
          Weight, Size, and x-height
               Aa Aa Aa         Aa         Aa Aa
               Different weights and stresses


Aa   Aa   Aa   Aa   Aa    Aa        Aa Aa
          Font sizes from 12 points to 96 points

                hd hd hd hd hd hd
                    Varying x-height
Chapter 2                       Theoretical Foundations of Multimedia
                    Typography —
                      Alignment




   Left Justified   Right justified     Justified          Centered
Chapter 2                             Theoretical Foundations of Multimedia
           Typography —
       Special Type Techniques




Chapter 2          Theoretical Foundations of Multimedia
            Production of Sound

• Equilibrium— An object at rest; the mid-
  point of the motion of vibration
• Independence of magnitude and period —
  accounts for the independence of volume
  and pitch
• Speed of a point in vibration varies — as
  vibration proceeds, a point reaches maxi-
  mum speed as it passes the equilibrium
  point, then slows until it reaches it maxi-
  mum swing, reverses itself and begins to
  speed up again
Chapter 2                Theoretical Foundations of Multimedia
              Sound Waves

• Frequency — number of vibrations per
  second; determines the pitch
• Amplitude—the intensity or volume of a
  heard sound, or the signal strength of an
  electronically transmitted sound
• Harmonics — waves having frequencies
  related by arithmetic ratios; account for
  the different sounds of different instru-
  ments, even though they are playing the
  same note
Chapter 2               Theoretical Foundations of Multimedia
            Harmonic Motion

                                          At rest



                                         Compressing



                                          Rarefying


                                          Wave motion



Chapter 2           Theoretical Foundations of Multimedia
     Fourier Spectrum Analysis

• Baron Jean Baptiste Joseph Fourier
• “Any vibration that repeats itself indef-
  initely can be built up from (or is analyz-
  able into) a set of pure sinusoid waves”
                                         Handel (1993)


• “Any periodic waveform, no matter how
  complex, can be analyzed, or decom-
  posed, into a set of simple sinusoid waves
  with calculated frequencies, amplitudes,
  and phase angles”
                                         Handel (1993)
Chapter 2                 Theoretical Foundations of Multimedia
     Fourier Spectrum Analyses




Chapter 2         Theoretical Foundations of Multimedia
            Propagation of Sound

• Reflection— sound waves bounce off of
  surfaces and continue to travel in a new
  direction
• Direct sound —sound heard after no
  reflections
• Early sound — sound heard after only one
  reflection
• Reverberation — sound heard after several
  reflections
Chapter 2               Theoretical Foundations of Multimedia
            Propagation of Sound




Chapter 2              Theoretical Foundations of Multimedia
              Doppler Effect

• When either the source or the listener is
  in motion relative to the other, the wave-
  length of the soundwaves is affected,
  causing the pitch to seem to vary
• The pitch becomes increasingly higher as
  the source approaches the listener
• The pitch becomes increasingly lower as
  the source recedes from the listener
• The relative motion must be at least 20 or
  30 miles per hour
Chapter 2                Theoretical Foundations of Multimedia
            Listening and Auditory
                Communication
• Hearing — merely receiving sound physi-
  cally, not consciously
• Listening — “is perceiving sound with
  careful and responsive discrimination. It
  is thinking about sound — analyzing its
  quality, style, interpretation, and nuance.
  It is trying to understand what motivates a
  sound. It is engaging in new sonic exper-
  iences regardless of their strangeness. It
  is examining your reaction to sound in
  relation to your mood and feeling.” Alten, 1994
Chapter 2                  Theoretical Foundations of Multimedia
            Reception of Sound

• Habituation — 85% of all primary auditory
  neurons become less sensitive to sounds
  if they persist unchanged. Musicians use
  changes in key and vibrato to counteract
  this phenomenon
• Pitch — Most adults can detect pitches
  between 20 and 20,000 Hz, but pitches
  above 16,000 Hz are perceived as hiss.
• Relationship to age — As age increases,
  range of hearing decreases.
Chapter 2               Theoretical Foundations of Multimedia
Chapter 2   Theoretical Foundations of Multimedia
  Comparison of Changes in Decibels
             and Power
     D dB   D Power   D dB          D Power
       0        1      15                32
       1        1.3    18                64
       2        1.6    20               100
       3        2      30             1,000
       4        2.5    40            10,000
       5        3.2    50           100,000
       6        4      60         1,000,000
       7        5      70        10,000,000
       8        6      80       100,000,000
       9        8      90     1,000,000,000
      10       10     100    10,000,000,000
      11       12     110   100,000,000,000
      12       16     120 1,000,000,000,000
Chapter 2             Theoretical Foundations of Multimedia
            Perception of Sound

• Hearing Levels — physical, abstract, etc.

• Meaning — is derived from relationships
  among the various levels on which
  humans hear sounds

• Localization — is the ability to locate a
  sound source in three-dimensional space
• Identification — is the ability to recognize
  voices, instruments, and other sources of
  sounds
Chapter 2                Theoretical Foundations of Multimedia
      Handel’s Approaches to
 Conceptualizing Perception of Sound
• Prototype or template — compare what is
  heard with an idealized version

• Feature or attribute — abstract critical
  features to distinguish among possibilities
• Higher-order variable — time-varying,
  complex acoustic properties that uniquely
  identify an event
• Innate systems — distinct brain structures
  that yield invariant precepts
Chapter 2               Theoretical Foundations of Multimedia

				
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