Lighting Terminology: Delivered Lumens, CBCP, Footcandles and More
When reading a lighting label, you may see different measurements, such as lumen count, CBCP and color temperature. To understand different lighting terms and metrics better, exploring the definition of these terms and their place in lighting products and installation may help you decide which lighting fixture to use. Finding the right product can help you illuminate your space appropriately.
Here are nine lighting terms to keep in mind:
Lumens are a metric that measures a light’s potential to produce brightness. Specifically, it measures luminous flux, or the amount of light produced by a light source. For example, omnidirectional lamps or fluorescent tubes may not use all of their lumens. In the case of omnidirectional lamps, some light may travel upward, reach sideways or be directed at a specific area or product displayed.
Lumens explain how much light a particular fixture can produce, and the number of delivered lumens tells you what it actually produces. Remember that more lumens may not always mean the lighting will be bright.
Candelas, or candlepower, are a unit that measures the luminous intensity of a light source. This intensity can be measured in a specific space or direction and often refers to the power generated by the fixture. Typically, one candela equals the amount of light an ordinary candle produces.
While candelas measure the intensity of a light source itself, a footcandle is a measurement of how intense one light source affects an object or room. Measuring the illuminance cast on a surface from one light source can be especially useful when comparing different types of lights, such as traditional incandescent lights versus modern LEDs.
This measurement also refers to the number of lumens contained in the square footage of a space, with one footcandle equalling one lumen per square foot. When measuring delivered lumens, footcandles focus on the quantity of light as it impacts a surface. Depending on how far away the light source is from the object, the fixture can lose light as it travels throughout the room. To the typical observer, this loss can be caused by the distance or direction of the fixture.
Footcandles are one of the most important metrics used in lighting, as the Occupational Safety and Health Administration (OSHA) requires that safety standards be measured using footcandles.
Lux measures the lumens in a square meter rather than a square foot. Like the imperial and metric measuring systems, the lux and footcandle systems are relatively similar in how they quantify lumens.
One lux equals one lumen per square meter. You can calculate lux easily if you know the area of a space in square meters. To convert lux to footcandles, divide the number in lux by 10.7. Lux is considered a precise and reliable way to measure lumens and attempts to quantify the amount of light that will impact a specific area.
Illuminance refers to the light hitting a surface and the lumens that exist within the area. Footcandles and lux quantify the idea of illuminance when making measurements using lumens per square foot or per square meter, respectively.
6. Beam Angle
The beam angle is the angle of light that a fixture emits. A wider beam angle means that your light will be less intense, whereas a narrow or focused beam angle means a brighter emission.
7. Beam Spread
The beam spread refers to the amount of surface illuminated by a light source. While it does not account for the field spread or the outer area lit up by a fixture, you can use the beam angle to calculate the beam spread and discover the distance a light source may reach.
8. Center Beam Candlepower (CBCP)
Center beam candlepower refers to a light source’s output in the center of the fixture’s beam. For installations that require directional lighting, such as floodlights in a stadium or overhead lights in a warehouse, center beam candlepower can measure the intensity of a light source when it hits a specific area.
CBCP can be especially important if you want to aim light in a specific direction, but it may not be the most accurate when mapping out a lighting plan. You should also know that lights with the same lumen rating may have different center beam candlepower measurements.
9. Correlated Color Temperature
The correlated color temperature tells you how warm or cold a light appears and is measured in Kelvins. Most color temperatures can range from 2,200 to 6,500 Kelvins. For example, warmer lights like red, orange or yellow will have low color temperatures. Cool blue lights will have higher color temperatures, anywhere above 4,000 Kelvins.
Depending on where you plan to install light fixtures, different lights may be more suitable than others. A warehouse, for example, may need more lighting than a restaurant or a storefront. OSHA also has lighting requirements for workplace safety that measure light using footcandles.
How Much Light Is Needed?
To make a lighting plan or photometric study, you’ll want to write out a detailed account of the light levels and distribution needed for the location. Whether you install the lights indoors or outdoors, online software can create most lighting plans and help you calculate lighting levels, predict balance and simulate the fixtures’ heights and locations.
OSHA has standards for industrial and commercial workplaces to ensure the lighting is bright enough but doesn’t produce excessive glare or brightness. Lighting that’s too bright or too dim can be dangerous and cause headaches or eyestrain in employees. When creating a lighting plan, you may find it helpful to use a lumens calculation to predict how the light may act within a space. Remember that adding more lights will cause the footcandle measurements to increase.
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