CLD Interior Lighting 3 — Questions and Answers
Question 1: A lighting designer specifies a fixture with a beam angle of 15°. This fixture would most likely be used for:
- General ambient illumination across an open plan office
- Wall washing a large textured surface
- Spotlighting a sculpture or architectural feature (Correct answer)
- Emergency egress lighting in a corridor
Correct answer: Spotlighting a sculpture or architectural feature
A narrow 15° beam angle concentrates light into a tight cone, ideal for accent and spotlighting applications where precision is required.
Question 2: In interior lighting design, 'contrast ratio' between a task area and its immediate surround is recommended by IESNA to be no greater than:
- 10:1
- 3:1 (Correct answer)
- 1:1
- 20:1
Correct answer: 3:1
IESNA guidelines recommend a maximum luminance contrast ratio of 3:1 between the task and its immediate surround to prevent visual fatigue.
Question 3: Which photometric distribution type describes a luminaire that emits the majority of its light downward between 0° and 60° from nadir?
- Semi-direct
- Direct (Correct answer)
- Indirect
- Direct-indirect
Correct answer: Direct
A direct luminaire directs 90–100% of its luminous flux downward, providing efficient illumination of horizontal surfaces with minimal uplight.
Question 4: A CLD candidate is reviewing a photometric report. The 'zonal lumen summary' is most useful for:
- Determining the fixture's color rendering index
- Calculating the total lumens emitted in each vertical angular zone (Correct answer)
- Identifying the fixture's beam spread in the horizontal plane
- Measuring flicker index values
Correct answer: Calculating the total lumens emitted in each vertical angular zone
The zonal lumen summary tabulates lumens emitted within defined vertical angular zones (e.g., 0–30°, 30–60°, 60–90°), aiding spacing and efficiency calculations.
Question 5: What is the primary purpose of a 'light shelf' in interior daylighting design?
- To store spare lamps near the window
- To block all direct sunlight from entering the space
- To redirect daylight deeper into the space while shading the lower window zone (Correct answer)
- To increase privacy by obscuring sightlines
Correct answer: To redirect daylight deeper into the space while shading the lower window zone
A light shelf is a horizontal reflecting surface positioned at window head height to bounce daylight onto the ceiling and deeper into the interior while shading occupants near the window.
Question 6: In a healthcare examination room, the recommended maintained illuminance level on the horizontal task plane is typically:
- 100 fc (1,000 lux)
- 50 fc (500 lux) (Correct answer)
- 10 fc (100 lux)
- 200 fc (2,000 lux)
Correct answer: 50 fc (500 lux)
IESNA RP-29 recommends approximately 50 fc (500 lux) for general examination tasks in healthcare facilities, balancing visibility with patient comfort.
Question 7: Which of the following best defines 'Color Rendering Index (CRI)' in practical terms?
- The total light output of a source in lumens
- A scale measuring how accurately a source renders colors compared to a reference illuminant (Correct answer)
- The ratio of visible light to total energy consumed
- The dominant wavelength peak of a light source in nanometers
Correct answer: A scale measuring how accurately a source renders colors compared to a reference illuminant
CRI (Ra) is a 0–100 scale indicating how faithfully a light source reproduces the colors of objects compared to a reference source of the same CCT.
CLD Interior Lighting 3
A lighting designer specifies a fixture with a beam angle of 15°.
This fixture would most likely be used for: