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Transcript of Key objectives in Lighting design - MIT OpenCourseWare · Key objectives in Lighting design Visual...
Key objectives in Lighting design
Visual performance
Physiological conditions
Visual qualityno strong "contrasts"good "color rendering"adequate "light levels"no "disturbing reflections"no direct "glare"
Radio- and photometric quantities
Radiometry vs. Photometryabsolute (energy)
vs. V(λ)-dependent (light)
350 400 450 500 550 600 650 700 750 800
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Wavelength [nm]
Rel
ativ
e Ef
ficie
ncy
[-]
Image by MIT OCW.
Radio- and photometric quantities
Radiometry vs. Photometryabsolute (energy)
vs. V(λ)-dependent (light)
1.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
350 400 450 500 550 600 650 700 750 800
Wavelength (nm)
Rel
ativ
e ef
ficie
ncy
[-]
Image by MIT OCW.
Radio- and photometric quantities
Four major quantitiesfluxilluminanceintensityluminance
Image by MIT OCW.
Radio- and photometric quantities
Fluxenergy / unit of time
φ in Watts [W] vs. lumen [lm]
Image by MIT OCW.
Radio- and photometric quantities
Fluxenergy / unit of time
φ in Watts [W] vs. lumen [lm]
683 lumen/Watt at 555 nm : φlum [lm] = 683 •Σ V(λ) •φe [W]
75 watts
1055 lumens
70 watts
5600 lumens
Incandescence Discharge
verydifferent
efficacies !
Images by MIT OCW.
Radio- and photometric quantities
Flux
Illuminanceflux received / unit of surface E in [W/m2] vs. [lm/m2] or lux [lx]
∆φ
∆S
Images by MIT OCW.
Radio- and photometric quantities
Flux
Illuminanceflux received / unit of surface E in [W/m2] vs. [lm/m2] or lux [lx]
Full moon Overcast sky Sunlight
0.01 Lux 8'000 - 20'000 Lux 100'000 Lux
Image by MIT OCW.
Radio- and photometric quantities
Flux
Illuminanceflux received / unit of apparent surface (cosine ("Lambert") law)E in [W/m2] vs. [lm/m2] or lux [lx]
α∆φ∆SE⊥ =
E
= = =
α α = E= E= E⊥. . cos ααα
Images by MIT OCW.
Radio- and photometric quantities
Flux
Illuminanceflux received / unit of apparent surface (cosine ("Lambert") law)E in [W/m2] vs. [lm/m2] or lux [lx]measurement with lux-meter (illumance-meter)
Requirements Lux Examples
Low 20-70 Circulation, stairs
Moderate 120-185 Entrance, restaurant
Medium 250-375 General tasks
High 500-750 Reading, Writing
Very high > 1000 Precision tasks
Radio- and photometric quantities
Flux
Illuminanceflux received / unit of apparent surface (cosine ("Lambert") law)E in [W/m2] vs. [lm/m2] or lux [lx]measurement with lux-meter (illumance-meter)exitance M for emitted flux [lux]
Radio- and photometric quantities
Flux
Illuminance
Intensityflux emitted "in a certain direction"
∆Ω
∆φ
Images by MIT OCW.
Radio- and photometric quantitiesFlux
Illuminance
Intensityflux emitted within a certain solid angle
d
∆Ω∆Ω
∆A
∆A = ∆Ω.d2
d2∆A
∆Ω = = = = = = =
Images by MIT OCW.
Radio- and photometric quantities
Flux
Illuminance
Intensityflux emitted within a certain solid angleI in [W/sr] vs. [lm/sr] or Candela [Cd]
1 Candela = intensity of one candle
Radio- and photometric quantities
Flux
Illuminance
Intensityflux emitted within a certain solid angleI in [W/sr] vs. [lm/sr] or Candela [Cd]inverse square law for point source
E = I cos(θ) / d2
θd
Image by MIT OCW.
Radio- and photometric quantities
Flux
Illuminance
Intensityflux emitted within a certain solid angleI in [W/sr] vs. [lm/sr] or Candela [Cd]inverse square law for point sourceintensity distribution
400
300
200
100
330o
300o
270o
240o 120o
90o
60o
30o
Image by MIT OCW.
Radio- and photometric quantitiesFlux
Illuminance
Intensityflux emitted within a certain solid angleI in [W/sr] vs. [lm/sr] or Candela [Cd]inverse square law for point sourceintensity distribution
h = 10 ft d
30°
200
180
160
140
120
10080
60
40
0o 15o30
o
45o
60o
75o
90o
105o
120o
135o
150o
165o180
o
180 cd
Image by MIT OCW.
Radio- and photometric quantities
Flux
Illuminance
Intensity
Luminanceflux emitted by apparent surface in a given direction≈ I/m2 (or M/sr)L in [Cd/m2]
∆I
∆Ω∆φ
∆Ss
Source Ns
θ
Images by MIT OCW.
Radio- and photometric quantities
Flux
Illuminance
Intensity
Luminanceflux emitted by apparentsurface in a given direction≈ I/m2 (or M/sr)L in [Cd/m2]
S
L = I / (S . cos θ)L = I / Sa
Sa
θ
Radio- and photometric quantities
Flux
Illuminance
Intensity
Luminanceflux emitted by apparentsurface in a given direction≈ I/m2 (or M/sr)L in [Cd/m2]
Intensity variation Luminance variation
lambertian surface lambertian surface
Specular
Diffuse/Specular Specular/Spread Diffuse/Spread
Spread Diffuse
Image by MIT OCW.
Radio- and photometric quantities
Flux
Illuminance
Intensity
Luminanceflux emitted by apparentsurface in a given direction≈ I/m2 (or M/sr)L in [Cd/m2]
Primary sources• Sun• Incandescent lamp (100 W, bright)• Incandescent lamp (100 W, frosted)• Fluorescent tube (40 W, 38 mm)• Candle• Computer screen
Cd/m2
1 650 000 0006 000 000
125 0005000 - 8000
5000100-200
Radio- and photometric quantities
Flux
Illuminance
Intensity
Luminanceflux emitted by apparentsurface in a given direction≈ I/m2 (or M/sr)L in [Cd/m2]
Cd/m2
2 500 - 3000100
505
Secondary sources• Moon• White paper (ρ = 0.8, E = 400 lux)• Grey paper (ρ = 0.4, E = 400 lux)• Black paper (ρ = 0.01, E = 400 lux)
Minimal luminance perceived: 10-5
Radio- and photometric quantities
Luminance measurementEye = luminance-meter
Photometry
Reading assignment from Textbook:“Introduction to Architectural Science” by Szokolay: § 2.1
Additional readings relevant to lecture topics:"IESNA Lighting Handbook" (9th Ed.): pp. 2-1 to 2-3 + pp. 3-1 to 3-5 + pp. 3-9 to 3-14 + pp. 4-1 to 4-6