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Visual comfort
Key aspects of daylit environmentVisual performancePhysiological conditionsVisual quality
Visual comfort
Key aspects of daylit environment
ObjectivesHarmonious luminance distribution (no strong contrasts)Good color rendering (continuous spectrum, appropriate color T°) Adequate illuminance levelNo disturbing reflectionsNo direct glare
Visual comfort
Key aspects of daylit environment
Objectives
Recommended illuminances
Illuminance [lux]Type of space and function Min Mid MaxCirculation, corridors, theatres, concert halls 50 100 200Workshops, retail centres 200 300 400Schools, offices, usual tasks, reading, writing, computer work, … 300 400 500
Delicate work, drawing, technical tasks, ... 500 750 1000Precision workshops, clockwork, color control, visual quality control, … 1000 to 5000
Visual comfort
Visual adaptation
1
/m2
1j/m
2
10 100 1000 0.01
Adaption Level cd
0.1
10
100
Glare
Black Shadow Ob
ect L
umin
ance
cd
1000
10000
100000
Useful Range of Discrimination
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual fieldcentral field (fovea)ergorama (cones)panorama (rods)
oo
o o
o
o
o o
o
o
o 0o
330210
240Panorama Ergorama
270300
30
6090
120
150
180 70 50 30 10
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual fieldcentral field (fovea)ergorama (cones)panorama (rods)
THE EYE'S THREE COLOR RECEPTORS
4000
"Blue"Cones
"Green"Cones
"Red"Cones
Violet Blue Green Yellow Red
5000
Wavelength (angstroms)
Res
pons
e
6000 7000
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual fieldcentral field (fovea)ergorama (cones)panorama (rods)
3
1
Panorama Ergorama
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual fieldcentral field (fovea)ergorama (cones)panorama (rods)
1
1
Ergorama
10 10
Panorama
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual field
Visual performanceperson & taskilluminance on work planeluminance contrastvisual fatigueexample: work place
Visual comfort
Visual adaptation
Visual field
Visual performance
Glarephysiological (disability)psychological (discomfort)
Visual comfort
Visual adaptation
Visual field
Visual performance
Glarephysiological (disability)psychological (discomfort)sources: glazed openings & sun patches
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual field
Visual performance
Glarephysiological (disability)psychological (discomfort)sources: glazed openings & sun patches specular reflections
Image by MIT OCW.
Visual comfort
Visual adaptation
Visual field
Visual performance
Glarephysiological (disability)psychological (discomfort)sources: glazed openings & sun patches specular reflections inappropriate electric lights
Image by MIT OCW.
Visual comfort
Users’ preferencesnatural lightingopen viewvisual effectsharmonious colorsspecific conclusions daylight sunlight windows
Color perception
Apparent color depends onobserver
Image by MIT OCW.
Color perception
Apparent color depends onobserver
intrinsic color of objectintrinsic color of source
Color perceptionApparent color
=+Emission spectrum Reflection spectrum Resulting spectrum
reflexion emiss
ion
=+ emiss
ion
refle
xion
=+
refle
xionem
issi
on
Emission spectrum Reflection spectrum Resulting spectrum
Emission spectrum Reflection spectrum Resulting spectrum
Images by MIT OCW.
Color perceptionApparent color
=+Emission spectrum Reflection spectrum Resulting spectrum
reflexion emiss
ion
=+ emiss
ion
refle
xion
Emission spectrum Reflection spectrum Resulting spectrum
=+Emission spectrum Reflection spectrum Resulting spectrum
Images by MIT OCW.
Color perception
Apparent color
Image by MIT OCW.
Color temperature
Color temperature
Color temperature
Color temperature
Color temperature
Color temperature
Color temperature and visible emission
Source requirementscontinuous spectrum
color T° ≈ 5500°K
only fulfilled by daylight
< 5500 °K 5500°K > 5500°K
Color temperature
Color comfort
10
1750 2000 2250 2500 3000 4000 5000 10,000
20
50
100
200
500300
E
Tc (K)
1000
2000
5000
10000
20000
50000(Lux)
TOO "WARM"
COMFORTABLE
TOO "COLD"
Image by MIT OCW.
Visual Comfort, Colors
Reading assignment from Textbook:“Introduction to Architectural Science” by Szokolay: § 2.2
Additional readings relevant to lecture topics:"How Buildings Work" by Allen: Chap 13
"Heating Cooling Lighting" by Lechner: Chap 12