Outdoor Lighting Flashcards

A roadway lighting project requires maintained average luminance of 1.0 cd/m² at end of design life. If the initial design delivers 1.4 cd/m², what Light Loss Factor (LLF) was assumed?

Answer: 0.71

LLF = maintained value ÷ initial value = 1.0 ÷ 1.4 ≈ 0.71, meaning the designer accounted for ~29% depreciation over the design life.

Which ANSI/IES standard specifically addresses outdoor sports and recreational area lighting?

Answer: IES RP-6

IES RP-6 'Sports and Recreational Area Lighting' provides illuminance recommendations, uniformity criteria, and glare ratings for various sports and competition levels.

An outdoor museum facade luminaire uses a narrow-beam (10°) LED projector. Technicians report color shift across the beam at the edges. What is the most likely cause?

Answer: Chromatic aberration from the lens design separating phosphor emission wavelengths at oblique angles

Narrow-beam lenses can exhibit chromatic aberration at the beam edge where light passes through at oblique angles, causing blue or yellow fringing from the phosphor-converted LED source.

For a high-mast lighting installation (pole height ≥20m), which factor most significantly increases maintenance costs compared to standard-height pole lighting?

Answer: Requirement for bucket-truck or climbing access to service the luminaire head

High-mast poles require specialized access equipment (bucket trucks or lowering rings) for maintenance, making each service visit substantially more expensive than for standard pole heights.

A landscape architect requests 'moonlighting' for a garden. Which technique best achieves this effect?

Answer: Mounting warm-white fixtures high in tree canopy aimed downward to cast dappled shadows

Moonlighting places warm-white luminaires high in tree branches angled downward, mimicking the natural appearance of moonlight filtering through a canopy and creating natural shadow patterns below.

In the context of the IDA/IES Model Lighting Ordinance, 'Backlight-Uplight-Glare (BUG) ratings' serve which primary design function?

Answer: Quantifying light emitted rearward, upward, and at high angles as separate zonal values for code compliance

BUG ratings provide three separate zonal flux values — Backlight, Uplight, and Glare — allowing designers to verify MLO compliance for each emission direction independently.

Which approach best reduces 'spill light' onto an adjacent residential property from a commercial parking lot?

Answer: Selecting luminaires with asymmetric Type II or III distributions aimed inward

Asymmetric Type II or III distributions concentrate light toward the interior of the lot while limiting emission toward the property line, reducing spill onto adjacent residential properties.