CLC Lighting Calculations & Software 2 — Questions and Answers
Question 1: In AGi32 or DIALux, what does the 'calculation grid' spacing setting control?
- The density of illuminance sample points across a surface (Correct answer)
- The number of luminaires placed per zone
- The beam spread angle of each fixture
- The color rendering index output resolution
Correct answer: The density of illuminance sample points across a surface
Calculation grid spacing determines how many sample points are evaluated per unit area, affecting result accuracy and computation time.
Question 2: A maintained illuminance value in a lighting design accounts for which factor?
- Only initial lamp lumens
- Only luminaire optical losses
- Light loss factors applied to initial illuminance over time (Correct answer)
- Voltage fluctuations in the electrical system
Correct answer: Light loss factors applied to initial illuminance over time
Maintained illuminance equals initial illuminance multiplied by the light loss factor, representing real-world conditions after aging and dirt accumulation.
Question 3: Which IES photometric file format is the current standard used by most US manufacturers?
- LDT
- IES LM-63 (Correct answer)
- EULUMDAT
- TM-30
Correct answer: IES LM-63
IES LM-63 is the IESNA standard format for electronic transfer of photometric data and is widely used by US luminaire manufacturers.
Question 4: In a zonal cavity calculation, the cavity ratio (CR) formula uses which room dimensions?
- Area and perimeter only
- Height, length, and width of the cavity (Correct answer)
- Ceiling height and floor area only
- Mounting height and beam angle
Correct answer: Height, length, and width of the cavity
The cavity ratio formula is CR = 5h(l+w)/(l×w), using the cavity height, length, and width.
Question 5: What is the purpose of the 'Obstructed Sky Model' in daylighting simulation software?
- To calculate electric lighting energy savings
- To model sky luminance blocked by surrounding buildings or terrain (Correct answer)
- To simulate lamp color shift over time
- To compute glare index from direct sunlight
Correct answer: To model sky luminance blocked by surrounding buildings or terrain
The Obstructed Sky Model accounts for nearby structures or terrain that block portions of the sky dome, reducing available daylight.
Question 6: A designer calculates an average illuminance of 55 fc on a task surface. The target is 50 fc. What is the coefficient of utilization most likely scenario?
- The design is under-lit and needs more fixtures
- The design exceeds the target and may allow fixture reduction (Correct answer)
- The CU was calculated incorrectly and must be redone
- The maintained illuminance equals the initial illuminance
Correct answer: The design exceeds the target and may allow fixture reduction
When calculated illuminance exceeds the target, the designer may reduce fixture count or dimming to optimize energy use while meeting the standard.
Question 7: In photometric software, 'false color rendering' of an illuminance plot primarily helps designers to:
- Select lamp color temperatures for aesthetics
- Quickly identify areas of uniformity and hotspots visually (Correct answer)
- Calculate energy consumption per zone
- Determine fixture mounting heights automatically
Correct answer: Quickly identify areas of uniformity and hotspots visually
False color maps use a color spectrum to visually represent illuminance levels, making it easy to spot bright spots, shadows, and uniformity issues at a glance.
CLC Lighting Calculations & Software 2
In AGi32 or DIALux, what does the 'calculation grid' spacing setting control?