CLC Human Centric Lighting & Wellness 3 — Questions and Answers
Question 1: CIE S 026/E:2018 defines the α-opic action spectra for five photoreceptor types. Which receptor's action spectrum is used to calculate S-cone-opic EDI?
- Melanopsin (ipRGC)
- S-cone (Correct answer)
- M-cone
- Rod
Correct answer: S-cone
S-cone-opic EDI (Equivalent Daylight Illuminance) is calculated using the spectral sensitivity function of the short-wavelength sensitive (S) cone.
Question 2: An office measures 250 melanopic EDI at the eye. According to WELL v2 L07 Feature, is this sufficient for daytime circadian support?
- Yes, 250 melanopic EDI exceeds the 200 lux minimum
- No, WELL requires at least 150 melanopic EDI only at night
- No, WELL v2 requires at least 275 melanopic EDI for 4+ hours (Correct answer)
- Yes, any value above 100 melanopic EDI satisfies daytime criteria
Correct answer: No, WELL v2 requires at least 275 melanopic EDI for 4+ hours
WELL v2 Feature L07 requires a minimum of 275 melanopic EDI for at least 4 hours per day during daytime work periods to support circadian health.
Question 3: A lighting designer specifies luminaires with a high S/P ratio. What primary non-visual benefit does this provide?
- Reduced glare at the task plane
- Greater circadian effectiveness per photopic lumen (Correct answer)
- Lower energy consumption per watt
- Improved color fidelity at low light levels
Correct answer: Greater circadian effectiveness per photopic lumen
A high S/P (scotopic-to-photopic) ratio indicates relatively more short-wavelength content, which provides greater melanopic stimulation per photopic lumen.
Question 4: Which of the following is a limitation of using Correlated Color Temperature (CCT) alone to specify human centric lighting?
- CCT cannot be measured with standard photometers
- Two sources with the same CCT can have very different spectral power distributions and melanopic effects (Correct answer)
- CCT values above 5000K are not achievable with LED technology
- CCT does not correlate with color appearance for white light
Correct answer: Two sources with the same CCT can have very different spectral power distributions and melanopic effects
Two light sources with identical CCTs can differ significantly in their spectral power distributions and therefore have very different melanopic EDI values.
Question 5: In a dynamic HCL system, which sequence of color tuning throughout a standard workday best supports circadian alignment?
- Constant 4000K throughout the day
- High CCT morning, lower CCT midday, high CCT evening
- Low CCT morning, peak CCT at midday, decreasing CCT afternoon/evening (Correct answer)
- Random CCT variation every 30 minutes
Correct answer: Low CCT morning, peak CCT at midday, decreasing CCT afternoon/evening
Mimicking natural daylight, HCL systems should start moderate, peak in melanopic stimulation around midday, and taper to warmer, lower-melanopic light in the afternoon/evening.
Question 6: A neonatal intensive care unit (NICU) implements HCL. What is the primary wellness concern that differentiates NICU lighting from adult HCL applications?
- Neonates require higher illuminance for visual acuity development
- Premature infant circadian systems are not yet developed and blue light may cause retinal damage (Correct answer)
- NICU nurses require maximum alertness lighting 24 hours a day
- Standard WELL metrics apply without modification to NICU environments
Correct answer: Premature infant circadian systems are not yet developed and blue light may cause retinal damage
Premature neonates have immature circadian systems and underdeveloped retinal protective mechanisms, making them potentially vulnerable to blue light phototoxicity from high melanopic exposures.
Question 7: The biological day length (photoperiod) is sensed by the SCN primarily through the duration of which hormone's suppression?
- Cortisol
- Serotonin
- Melatonin (Correct answer)
- Adenosine
Correct answer: Melatonin
The SCN reads photoperiod via the duration of melatonin suppression — longer light exposure suppresses melatonin longer, signaling a longer 'day' to the body.
CLC Human Centric Lighting & Wellness 3
CIE S 026/E:2018 defines the α-opic action spectra for five photoreceptor types.
Which receptor's action spectrum is used to calculate S-cone-opic EDI?