Foot candles measure light intensity over a square foot. This helps you see if places like offices and museums are well-lit and have enough brightness for daily work or life.
Key Takeaways
- Foot candles measure light intensity on the surface of an object, while the lumen indicates the total light output from a lighting fixture.
- 1 lux is equal to 0.092903 foot-candles
- The unit of measurement for foot-candles can be expressed as foot-candle, fc, lm/ft², or ft-c.
- IES recommended light levels in fc (PDF)
What Are Foot Candles?
A foot-candle measures light intensity. The unit of measurement can be expressed as foot-candle, fc, lm/ft², or ft-c. It represents the illuminance on a one-square-foot surface from a consistent light source. if one lumen falls on one ft² rectangular area, then the rectangular area got one-foot candle readings
This measurement helps determine how well-lit a space is, making sure areas needing specific light levels get them. Unlike lumens, which measure the amount of light emitted by a source, one foot candle measures the light as perceived by the human eye over a given area.
Foot candle is predominantly used in the United States. Other parts of the world, such as Europe, use the SI-derived unit called “lux,” which measures light intensity over a one-meter square area. 1 lux is equal to 0.092903 foot-candles
What Is The Purpose Of A Foot-Candle?
The primary purpose of using foot candles is to ensure that spaces have enough illuminance for work. By using this measurement, lighting experts can design the lighting effect before projects commence.
In work environments, higher foot candle measurements can make tasks easier and reduce eye strain, while lower readings might suffice for areas where the light mainly serves to show the decor. Museums, for example, need specific light levels to protect sensitive artifacts and create the right ambiance. In horticulture, accurate foot candle readings ensure plants get the appropriate type and amount of light.
Recommended Foot Candle Levels for Various Spaces
The Illuminating Engineering Society (IES) provides guidelines on recommended lighting levels for various environments, ensuring adequate illuminance for different spaces.
Low-Light Areas (2-10 Foot Candles)
Outdoor walkways and parking lots typically need lighting levels between 2 to 10 foot candles. These levels ensure visibility and safety without being overly bright.
Medium-Light Areas (10-40 Foot Candles)
General office spaces and classrooms usually require about 10 to 20 foot candles. These levels are adequate for tasks needing more visibility without causing discomfort or eye strain. An office environment with proper lighting can boost employee productivity and reduce fatigue.
Indoor gymnasiums, workshops, and airports typically need lighting levels between 25 to 40 foot candles. These levels ensure safe and efficient activities, whether playing sports, working on detailed tasks, or navigating an airport terminal under a bright light.
High-Light Areas (40+ Foot Candles)
Commercial kitchens and laboratories require significantly higher foot candle levels. Commercial kitchens need a minimum of 60+ foot candles for chefs to prepare food safely and efficiently. Proper lighting in these environments is crucial to prevent accidents and maintain hygiene standards.
Factories and gyms typically require foot candle levels ranging from 40 to 55.
Laboratories are recommended to have foot candle levels between 75 to 120. This ensures scientists and researchers can conduct their work with precision and accuracy.
How to Measure Foot Candles
A sensitive light meter is the best tool for this job, placed on the illuminated surface to measure light intensity. This process, known as a type of photometry, focuses on how our eyes perceive light, distinguishing it from radiometry, which measures all radiant energy forms in absolute terms.
For businesses and organizations, understanding the lighting experience of customers and staff is critical. A light meter measuring in lux can easily convert to foot candles by dividing the lux value by 10.764. This conversion maintains consistency across different measurement units and ensures spaces are properly lit.
Comparing Foot Candles and Lux
Foot candles and lux both measure light intensity but differ in the area they cover. Foot candles measure light intensity over a square foot, making them standard in the United States. Lux measures light intensity over a square meter, a unit more commonly used in Europe and other parts of the world.
Converting between these units is straightforward: 1 lux equals 0.092903 foot candles.
Tools for Measuring Light Intensity
A light meter is the best tool for measuring light intensity and obtaining accurate foot candle readings. Regular calibration according to the manufacturer’s instructions is crucial for precise readings.
Basic light meters, like the ILT10C, are reliable and easy to use for straightforward foot candle measurements.
Advanced light meters, like the ILT5000, offer extensive features such as wireless technology and the ability to measure across a wide range of light intensities.
OSHA Lighting Standards and IES Recommendation
The Occupational Safety and Health Administration (OSHA) mandates specific lighting regulations to enhance workplace safety and productivity. These requirements emphasize evenly distributed lighting in work environments to prevent potential hazards. General construction areas, for example, need at least 5 foot-candles of illumination to ensure worker safety.
The IES also recommends specific foot candle levels for different environments, such as 10 foot-candles for parking garages. Regular monitoring and maintenance of workplace lighting are crucial for compliance with OSHA’s standards and to prevent potential hazards.
Meeting these requirements is essential for creating safe and productive workspaces.
Summary
Understanding foot candles and their importance in various environments is crucial for ensuring proper lighting. From determining the right foot candle levels for different spaces to measuring them accurately with light meters, proper illumination plays a vital role in safety, productivity, and overall well-being.
By adhering to recommended foot candle levels and OSHA standards, businesses and organizations can create well-lit environments that enhance efficiency and safety. Remember, the right amount of light can make all the difference, whether it’s in a workplace, a museum, or a public space.
