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Light > Performance: Lecture 6 > Flashcards

Performance: Lecture 6 Flashcards

1
Q

Stimulus to the visual system;

The ageing eye 6 things:

A
  1. Decreased ability to focus
  2. Decreased ability to accommodate
  3. Decreases ability to adapt
  4. Increased scattering of light
  5. Yellowing of the lens
  6. Neural changes
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2
Q

Stimulus to the visual system;

General:

A

Retinal illuminance
Contrast (luminance and color)
Visual size
Retinal image quality

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3
Q

What is retinal illuminance?

A

Determines the state of adaptation of the visual system.

NOT amount of light entering the eye

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4
Q

What is the visual size for resolution?

A

The angle the critical dimension of the stimulus subtends at the eye.
The larger the solid angle, the easier the stimulus is to detect

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5
Q

What is retinal image quality?

A

Sharp image

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6
Q

By what is retinal image quality defined?

A

The stimulus itself
Light scattering within the medium through which the light is transmitted
Ability of the visual system to focus the image on the retina

A smaller retina produces a better quality retinal image

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7
Q

Stimulus to the visual system is determined by an interaction between (3 things):

A

The object to be seen
The background
The lighting of both the object and the background

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8
Q

Why do most people wear glasses?

A

To improve the retinal image quality

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9
Q

The level of visual performance is determined by:

A

The stimulus

The operating state of the visual system

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10
Q

Visual tasks have three components:

A

Visual –> extracting features

Cognitive –> interpreting

Motor –> manipulation of stimuli

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11
Q

Visual comfort is characterized by:

A

individual differences
context
whole visual field

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12
Q

Four causes of visual discomfort:

A

Visual task difficulty

Under and overstimulation

Distraction

Perceptual confusion

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13
Q

Specific causes of visual discomfort:

A 
Insufficient light
Uniformity
Shadows
Glare and reflections
Flicker
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14
Q

4 Criteria for outdoor views:

A

Glazing materials

  • Min: Clear
  • Med: Undistorted
  • Max: Neutrally coloured

Outside distance of view

  • Min: > 6 meter
  • Med: > 20 m
  • Max: > 50 m

Horizontal side angle

  • Min: 14
  • Med: 28
  • Max: 54 graden

Number of layers

  • Min: Landscape
  • Med: Landscape + 1 other
  • Max: All layers
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15
Q

Definition of lighting quality

A

An outcome based definition:
“the extent to which the lighting installation meets the objectives and the constraints set by the client and the designer”

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16
Q

Advantages of outcome-based definitions:

A
  1. Results become the measure of success
  2. Context dependent
  3. Many physical and psychological processes that influence perception
17
Q

What are context modifiers for increase of maintained illuminance?

A

Visual work is critical
Errors are costly
Accuracy
Task area undertaken for a long time

18
Q

What are context modifiers for a decrease in maintained illuminance?

A

Task undertaken takes a short time

Task details are of an unusually large size or high contrast

19
Q

What is the primary design criterion for designing comfortable office lighting?

A

Illuminance

20
Q

Tolerances of uniformity depend on (4):

A
  1. Absence or presence of windows
  2. Individual lighting control
  3. Location of task area
  4. Context
21
Q

What is the preferred surround/task area luminance ratio ?

A

0.1 to 1, with its median at 0.4

22
Q

What is desired desk reflectance?

A

0.3

23
Q

Great variations in luminance distribution leads to:

A

Constant adaptation of the eyes

User gets tired more easily

24
Q

The eight forms of glare:

A 
Flash blindness
Paralyzing glare
Exposure to light bright enough to cause damage
Distracting glare
Dazzle or saturation glare
Adaptation glare
Disability glare
Discomfort glare
25
Q

What is the luminance threshold for overhead glare?

A

16500

26
Q

The five discomfort glare prediction systems:

A
  1. VCP –> visual comfort probability
  2. CGI –> CIE Glare index
  3. DGI –> Daylight glare index
  4. UGR –> CIE unified glare rating
  5. DGP –> Discomfort glare probability
27
Q

Differences between VCP CGI DGI UGR

A
  1. VCP (1963-1966) –> visual comfort probability
    Only for typically sized luminaire sources of light (no halogens or visible skies)
  2. CGI (1969) –> CIE Glare index
    Luminaire sources of glare
  3. DGI (1972) –> Daylight glare index
    First metric to consider large glare sources: sky through window
  4. UGR (1995) –> CIE unified glare rating
    Only for electrical lightsources, no daylight
  5. DGP (2005) –> Daylight glare probability
    Direct daylight & specular reflections are considered
28
Q

What glare rating is mostly used in indoor standards?

Which one most for daylight?

A
  1. UGR

2. DGP

29
Q

Five recommendations to limit glare

A
  1. Matte surface finish
  2. Bright ceiling and bright walls
  3. Arrangement of luminaires relative to the workspace below
  4. Luminance restrictions of the luminaire
  5. Increased luminous area of the luminaires

Light (10 decks)

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