Foot-Candle in Marine and LED Lighting Systems
Unit of Measurement
Definition
A foot-candle (fc) is a unit of illumination that measures the amount of light falling on a specific area. It represents the level of light that hits a one-square-foot surface from a distance of one foot away from a light source.
In simple terms, it tells you how much usable light actually reaches a surface, such as a deck, cabin table, or engine room workspace.
The lumen is the foundational unit that measures how much light a fixture produces, while the foot-candle measures how much of that light effectively illuminates a given area.
Foot-candle readings are influenced by several factors, including the distance between the light and the surface, the beam angle, and reflective surfaces nearby.
Understanding foot-candles is essential for designing marine lighting that provides the right level of brightness for safety, comfort, and visibility.
Factors That Affect Foot-Candle Measurements
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Distance between the light source and the illuminated surface
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Beam angle of the fixture and direction of light
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Mounting height of the light
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Surface reflectance, such as white fiberglass vs. teak decking
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Obstructions or shadows that block or absorb light
These factors determine how much light reaches a particular surface, which is especially important when lighting engine rooms, decks, or navigation areas.
Typical Light Level Guidelines
| Light Level (Foot-Candles) | Light Level (Lux) | Recommended Marine or Similar Space |
|---|---|---|
| 5–10 fc | 50–100 lux | Storage lockers, stairs, or under-deck areas |
| 10–30 fc | 100–300 lux | Lounges, restrooms, or loading zones |
| 20–30 fc | 200–300 lux | Cabins, dining areas, or living quarters |
| 30–50 fc | 300–500 lux | Galleys, workshops, reading areas, or electrical rooms |
| 75–120 fc | 750–1200 lux | Engine rooms or laboratories requiring detailed visibility |
These benchmarks help determine the appropriate lighting output needed for each onboard space.
Example of Foot-Candle in a Sentence
“The navigation lights on my boat need to produce at least 2.5 foot-candles of illumination to meet Coast Guard visibility requirements.”
Synonyms
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Lumen per square foot
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Lux
Related Terms
Why Foot-Candles Matter for Marine Lighting
Foot-candle readings help ensure proper illumination for different areas of a vessel. By understanding and applying the right light levels, you can:
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Prevent under-lit or over-lit areas on decks and in cabins
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Improve energy efficiency and visibility
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Enhance safety and comfort for passengers and crew
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Optimize placement and number of fixtures for even lighting coverage