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f.luxometer: iPad Pro
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Circadian and Color
61% as bright as daylight
1h:36 minute phase shift

Good for the office, but too bright after dark
What's this?
Melanopic lux = 101.20
What's this? 6896K
feels like 4968K
0.93 M/P ratio
What's this?
Circadian Metrics

Photoreceptor Responses
α-opic equivalent illuminance

S-cone (Cyanopic lux): 125
Melanopic lux: 101
Rod (Rhodopic lux): 106
M-cone (Chloropic lux): 107
L-cone (Erythropic lux): 104
CIE-recommended SI Units
α-opic spectrally-weighted irradiance

S-cone (Cyanopic): 9.43 µW/cm2
Melanopic: 12.2 µW/cm2
Rod (Rhodopic): 15.0 µW/cm2
M-Cone (Chloropic): 17.3 µW/cm2
L-cone (Erythropic): 18.0 µW/cm2
Action spectrum efficacy (Melanopic lux)

Actinic power / lux: 0.1116 µW/cm2
Actinic power / total power: 32.71%
ED50 (estimates)
Predicted half-saturation constant, based on 90lx Illuminant E equivalent

Total irradiance at ~ED50: 33.07 µW/cm2
Lux at ~ED50: 96.94
Quantal melanopic units (488nm equivalent)
Dacey 2005 (at cornea)

Irradiance: 2.99 x 1013 photons/cm2
Radiance: 1.07 x 1014 photons/cm2/sr

Retinal irradiance range: 5.82 x 1011 to 9.31 x 1012 photons/cm2
Or: 5.82 x 103 to 9.31 x 104 photons/µm2
Rea et al Circadian Light

Rea 2011 CLa: 158.1
Rea 2011 CS: 0.203

Additional Metrics

Blue Light Hazard

Blue light (weighted power): 10.1 µW/cm2
Blue light hazard factor (weighted power/lux): 0.0930 µW/cm2/lux
1h dose: 0.0365 J/cm2
12h dose: 0.438 J/cm2

Peak 'red': 560nm at 0.171 µW/cm2
Peak 'green': 540nm at 0.205 µW/cm2
Peak 'blue': 450nm at 0.419 µW/cm2

Peak wavelength: 450nm at 0.419 µW/cm2
Total irradiance (380-780nm): 37.2 µW/cm2 (0.372 W/m2)
Measurement & Model

Instrument: PR655
Simulated viewing distance: 15"
Scaling model (radiance to irradiance): 0.279

Photopic lux: 109.00
Photopic luminance: 390.8 cd/m2
S/P ratio: 2.18
Color Matching Functions

CIE 1931 x, y chromaticity: 0.3077, 0.3182
(XYZ: 0.1543, 0.1595, 0.1875)
CCT: 6896K with Duv=0.000145

CIE 1964 10-degree chromaticity: 0.3119, 0.3148
CCT: 6675K with Duv=-0.00420

CIE PO06 chromaticity: 0.3102, 0.3231
CCT: 6670K with Duv=0.00108

CIE 1931 2-degree (with Judd-Vos corrections): 0.3174, 0.3384
CCT: 6309K with Duv=0.00491
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