Ben Carter
Candlepower is a unit of measurement for luminous intensity. It is used to express levels of light intensity relative to the light emitted by a candle of specific size and constituents. Candlepower is measured using a light meter that detects intensity on target in Lux (SI unit) or Foot-candles (non-SI unit). The historical candlepower is equal to 0.981 candelas, and in modern usage, candlepower is sometimes used as a synonym for candela. While candlepower is valuable in certain contexts where directional intensity is a priority, lumens offer a more practical approach for assessing overall performance.
| Characteristics | Values |
|---|---|
| What is Candlepower | A unit of measurement for luminous intensity |
| What does Candlepower express | Levels of light intensity relative to the light emitted by a candle of specific size and constituents |
| What is the historical candlepower equal to | 0.981 candelas |
| What is the modern usage of candlepower | Synonym for candela |
| What is the term candlepower derived from | The Metropolitan Gas Act 1860, defined it as the light produced by a pure spermaceti candle weighing 1⁄6 pound (76 grams) and burning at a rate of 120 grains per hour (7.8 grams per hour) |
| What is Spermaceti | A material from the heads of sperm whales, used to make high-quality candles |
| What is the formula to calculate lumens from candlepower | Multiply candlepower by 12.57 |
| What is the formula to calculate candlepower from lumens | Divide lumens by 12.57 |
| What does candlepower quantify | The intensity of a light source in a specific direction |
| What is the difference between lumens and candlepower | Lumens measure the total amount of light put out whereas candlepower measures the intensity of the brightest part of the beam |
| When is candlepower a more relevant measure than lumens | When you need to know how much of a bulb’s energy is actually being collected and directed towards a target |
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What You'll Learn
Candlepower is a unit of luminous intensity
Candlepower, also denoted as cp or CP, is a unit of luminous intensity. It quantifies the intensity of light in a specific direction. The term originated from comparing the brightness of artificial light sources with the standard luminous intensity of a candle. In modern usage, candlepower is sometimes used interchangeably with candela.
The historical candlepower is equal to 0.981 candelas. This value was established in the United Kingdom by the Metropolitan Gas Act of 1860, which defined it as the light produced by a pure spermaceti candle weighing 1/6 pound (76 grams) and burning at a rate of 120 grains per hour (7.8 grams per hour). Spermaceti, derived from sperm whale heads, was used to make high-quality candles.
Candlepower is particularly useful when comparing lighting products for specific applications. For instance, if you need a light for long-range activities like search and rescue operations, security, or surveillance, the candlepower rating will be a more relevant factor than the lumen rating. This is because candlepower considers the performance of the entire fixture, including the lamp and reflector, to assess the brightness at a specific target point.
On the other hand, lumens measure the total light output of a source, encompassing all directions. Lumens are now the primary indicator of a light source's performance, as they allow for a comprehensive measurement that considers the entire light output. This is crucial for applications like street lighting, indoor illumination, and automotive lighting.
While candlepower is valuable in contexts where directional intensity is a priority, lumens offer a more practical approach for assessing overall performance and making informed decisions about lighting solutions.
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Candlepower vs Lumens
Candlepower and lumens are two different units of measurement for light intensity. Candlepower (CP) is a unit of measurement for luminous intensity, expressing levels of light intensity relative to the light emitted by a candle of specific size and constituents. The historical candlepower is equal to 0.981 candelas. In modern usage, candlepower is sometimes used as a synonym for candela.
Candlepower is a measure of the brightest part of the beam of a flashlight. It is a function of both the output of the lamp and the efficiency of the reflector. It measures the intensity of the light that hits a target at a distance, taking the performance of the whole fixture into consideration. This makes candlepower a more relevant measure than lumen output for searchlights and other focused light sources that will be used to illuminate specific targets at long ranges.
Lumens, on the other hand, is a measure of the total amount of light put out by a flashlight. Lumens are a useful measurement for floodlights and household light bulbs that will be used to illuminate a wide area directly around the bulb. Lumens become less valid when you need to know how much of a bulb’s energy is actually being collected and directed towards a target.
It is not possible to convert lumens to candlepower because these units measure different aspects of a light’s output. Depending on the fixture a bulb is placed in, a bulb with a high lumen rating may not necessarily have a high candlepower rating. For example, a laser has a very high candlepower because the light is focused into a single point, but it would have a very low lumen value because it does not give off a substantial amount of light.
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How to convert candlepower to lumens
Candlepower (abbreviated as cp or CP) is a unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents. Candlepower is also known as candela (cd), and a historical candlepower is equal to 0.981 candelas.
Lumens, on the other hand, are a unit of luminous flux, or the total amount of light emitted by a source. Lumens are especially useful when comparing lighting products as they provide a holistic view of their illuminating capabilities.
While candlepower and lumens measure different aspects of a light's output, there is a formula to convert candlepower to lumens:
> Lumens (lm) = Candlepower (cd) × Solid Angle (sr)
The solid angle represents the region over which the light spreads. For a point source, the solid angle is 4π steradians, which is the entire sphere surrounding the source.
It is important to note that several factors can influence the accuracy of the conversion from candlepower to lumens. These include the efficiency and design of the light source, as well as the presence of optical elements like lenses or reflectors that can modify the light's distribution pattern.
Additionally, it is worth mentioning that the Total Output system does not consider the focusing efficiency of the reflector, making it impossible to directly convert between peak beam candlepower and lumens.
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Peak beam intensity
Candlepower, or candela, quantifies the intensity of a light source in a specific direction, relative to the light emitted by a candle of specific size and constituents. It is a valuable measure when directional intensity is a priority, such as in search and rescue, security, or surveillance applications. By contrast, lumens measure the total light output of a source, encompassing all directions. Lumens are useful for floodlights and household light bulbs that need to illuminate a wide area directly around the bulb.
To measure peak beam intensity in candlepower, a light meter is used to detect the intensity of light hitting a target at a distance. The light meter is placed at a set distance from the light fixture, and the beam of light is directed at the probe. The candlepower measurement is then calculated by multiplying the light meter's Lux reading by the distance squared between the light source and the probe. This can be done using SI units (Lux and meters) or non-SI units (Foot-Candles and feet).
It is important to note that lumens and candlepower measure different aspects of a light's output. A bulb with a high lumen rating may not necessarily have a high candlepower rating, as the fixture and design can impact the candlepower measurement. Therefore, when comparing lighting products, it is beneficial to understand the terminology and measurements used to make an informed decision.
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History of candlepower
Candlepower (abbreviated as cp or CP) is a unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents.
The history of candlepower dates back to ancient times when candles were used for lighting. While there are no historical records of the first candles, clay candle holders from the 4th century B.C. have been discovered in Egypt. The Romans are credited with creating the wick candle, which they used to light homes and places of worship at night and to aid travellers. Early Asian candles were made with wax derived from insects and seeds moulded in paper tubes. The first known candle in America dates back to the first century A.D., when Native Americans burned oily fish (candlefish) wedged into a forked stick.
In the 15th century, candle-making moulds were first used in Paris, and present-day candle-making techniques began in the 13th century when travelling chandlers went door to door making dipped tapers from their clients' tallow or beeswax. However, the term "candlepower" was not defined until much later.
In the 19th century, there was a need for a better standard for luminous intensity. Jules Violle proposed a standard based on the light emitted by 1 cm^2 of platinum at its melting point in 1884. This unit of intensity, called the "violle", was approximately equal to 60 English candlepower. Despite the proposal, creating a standard based on this idea proved challenging due to the impact of impurities on the surface of the platinum.
The Metropolitan Gas Act of 1860 in the United Kingdom defined candlepower as the light produced by a pure spermaceti candle weighing 1/6 pound (76 grams) and burning at a rate of 120 grains per hour (7.8 grams per hour). Spermaceti, a substance derived from the heads of sperm whales, was used to make high-quality candles. This definition established a standardised unit of measurement for candlepower.
In the late 1930s, the Commission Internationale de l'Éclairage (International Commission on Illumination) and the CIPM proposed a "new candle" based on incandescent platinum. This proposal was promulgated by the CIPM in 1946, defining the brightness of the full radiator at the temperature of platinum solidification as 60 new candles per square centimetre. The unit was renamed "candela" in 1948 by the 9th CGPM.
Over time, the definition of candela has evolved. In 1967, the 13th CGPM amended the definition to specify the atmospheric pressure during the freezing of platinum. Further revisions were made in 1979 to address challenges with high-temperature Planck radiators and advancements in radiometry. The modern definition of candela, approved in 2018 as part of the 2019 revision of the SI system, is based on fundamental physical constants.
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Frequently asked questions
Candlepower is a unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents.
Candlepower is measured using a light meter that detects intensity on target in Lux (SI unit) or Foot-candles (non-SI unit). The light meter is set at a distance from the light fixture and the beam of light is pointed at the Light Meter’s probe.
Lumens are a measure of the total amount of light put out by a flashlight, whereas candlepower measures the intensity of the light that hits a target at a distance.
Yes, you can convert lumens to candlepower using the formula: Lumens (lm) = Candlepower (cd) x Solid Angle (sr). However, it is important to note that several factors can influence the accuracy of the result, such as the efficiency and design of the light source.
To convert candlepower to lumens, you can use the following formula: L=C/0.07958. For example, 200 candlepower would equal 2,513 lumens.
