Spectral Indices based on
biological processes sensitivity to
handle lighting applications
Antoine Morin-Paulhus1, Johanne Roby2 and Martin Aubé
Light Pollution Group, Cégep de Sherbrooke
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Existing lamp
characterization tools
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CCT - Correlated Color Temperature
Information given:
- high CCT => blue
lamp
- low CCT => yelloworange lamp
- Rough estimate of
some biological
impacts
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CRI - Color rendering index
Ability to distinguish colors
Lamp “safe” for street traffic?
Lamp efficient for workplace lighting?
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IPI - MSI - SLI Indices
Relative impact of commercial lamps on
biological processes and other phenomenons
IPI: Induced photosynthesis index
MSI: melatonin suppression index
SLI: Star light index
Based on the article by Martin Aube, Johanne Roby, Miroslav Kocifaj :
Evaluating Potential Spectral Impacts of Various Artificial Lights on Melatonin Suppression,
Photosynthesis, and Star Visibility
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Building Spectral Indices
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1- We start with a lamp spectrum
Example: Randomly picked LED lamp
8 watt Ledtech lamp with CCT = 5896K
http://galileo.graphycs.cegepsherbrooke.qc.ca/app/en/lamps/2470
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2 - We need a reference for comparison
D65 standard
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Normalization - 1/5
3 - Normalization
Lamp spectras contain relative values
Same lamp different distance
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Normalization - 2/5
Total intensity normalization
D65 Spectral Power Distribution
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Normalization - 3/5
Constant lumen normalization equation
Photopic curve
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Normalization - 4/5
Constant lumen normalization
These lamps have same intensity perceived by the human eye
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Normalization - 4/5
Constant lumen SPD: Sun vs LED
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4 - Compare the lamp with an experimental
impact spectrum
Example: Melatonin Suppression Action Spectrum
Data from :
- Thapan K, Arendt J, Skene DJ (2001) An action spectrum for melatonin suppression: Evidence for a novel non-rod, non-cone photoreceptor system in
humans. J Physiol 535(1): 261–267.
- Brainard GC, Hanifin JP, Greeson JM, Byrne B, Glickman G, et al. (2001) Action spectrum for melatonin regulation in humans: Evidence for a novel
circadian photoreceptor. J Neurosci 21(16): 6405–6412.
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Multiplication of lamp spectra by relative
impact spectra
2 curves (red and green) and their multiplication (blue)
The area
given by:
Is bigger when
spectra overlap
with big values
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Multiplication of spectra
Lamp spectrum
Melatonin suppression action spectrum
Φlamp(λ) = relative intensity for
wavelength λ
M(λ) = relative melatonin suppression
for wavelength λ
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Creating a Spectral Index
Equation:
Visually:
MSAS
Lamp
•
D65
•
MSAS
(Melatonin suppression index)
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MSI - Melatonin Suppression Index
Interpreting the values:
0 : Lamp has no impact on Melatonin Supp.
0.5 : half the impact of D65
1 : has the same impact as the D65
Gives insight about:
● Circadian rhythm impact
● When to use a lamp
● Impact of streetlights on human beings
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IPI - Induced Photosynthesis Index
Photosynthesis Action Spectrum
Use cases:
● Estimate plant growth
● Find exterior lighting impact on plants
Average photosynthesis action spectrum from
DIN 5031–10 (2000) Optical radiation physics and illuminating engineering - Part 10: Photobiologically effective radiation, quantities, symbols
and action spectra. Germany: Deutsches Institut Fur Normung EV (German National Standard).
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SLI - Star Light Index
Scotopic Spectral Sensitivity
Possible use case:
● Designing streetlights that preserves star visibility
● Regulation for dark sky reserves ?
Scotopic spectral sensitivity data from
Wyszecki G, Stiles WS (1982) Color science: concepts and methods, quantitative data and formulae, second edition. New York: Wiley. 935 p.
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LSPDD - Lamp Spectral Power Distribution Database
● 170+ lamp spectra
○
○
MSI, IPI, SLI, CCT & more
Raw spectrum data (TSV)
● Find lamps with
filters
○
by indices / cct / etc.
How to access?
lspdd.org
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LSPDD - Lamp types
Streetlights
Domestic lamps
Luminotherapy
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Conclusion
- Spectral indices provide a simple way to indicate lamp impact on
biological processes / night sky observation.
- Different impact spectras could lead to new indices using roughly
the same method and normalization.
- Any help expanding the LSPDD with lamp spectra from other parts
of the world would be highly interesting.
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Using the indices and the database
to better handle lighting
Morning (Ex: kitchen)
MSI : 0.6 -> Relatively high impact: awakes you
CCT : 5000K
Evening (Ex: livingroom/bedroom)
MSI : 0.2 -> Low impact: less tendency to awake you
CCT : 2500K
Around the house
SLI : 0.17 -> Low impact: better for dark sky
IPI : 0.55
MSI : 0.04
CCT : 1800K
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