Light Intensity Unit Converter
1 Candela (cd) = 12.57 Lumen (lm)
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Light Intensity Units
From architectural design to photography — light intensity units illuminate our understanding of how we perceive brightness, enabling scientists, engineers, and designers to create environments that are both functional and visually pleasing.
Common Light Intensity Units
Different aspects of light measurement use specialized units to quantify brightness, illumination, and light output:
Luminous Intensity and Flux Units
- Candela (cd): The SI base unit of luminous intensity, measuring the brightness of a light source in a specific direction. One candela approximates the light intensity of a common candle. Used to measure focused light sources like spotlights and LEDs.
- Lumen (lm): The SI unit of luminous flux, measuring the total amount of visible light emitted by a source in all directions. A standard 60W incandescent bulb produces about 800 lumens. Commonly used on light bulb packaging to indicate brightness.
- Candlepower (cp): A historical unit of luminous intensity that predates the candela, based on the light produced by a standard candle. While largely replaced by the candela in scientific contexts, it still appears in some lighting specifications.
- Millicandela (mcd): Equal to 1/1000 of a candela, frequently used for measuring the intensity of LEDs and small display lights in electronic devices where precise low-level light measurement is needed.
Illuminance Units
- Lux (lx): The SI unit of illuminance, measuring the amount of light that falls on a surface. One lux equals one lumen per square meter. Used in architectural lighting, workplace safety standards, and photography to ensure proper lighting levels.
- Foot-candle (fc): The imperial unit of illuminance, equal to one lumen per square foot or approximately 10.76 lux. Still commonly used in North America for lighting specifications in construction and theatrical lighting design.
- Phot (ph): An older CGS unit of illuminance equal to 10,000 lux (one lumen per square centimeter). Rarely used today except in some specialized scientific literature and historical contexts.
- Nox: A unit representing very low levels of illuminance (0.001 lux), sometimes used in astronomy and night vision applications to quantify the minimum light levels detectable by the human eye.
History of Light Measurement
Our journey to quantify and standardize light measurement reflects humanity's enduring relationship with illumination:
-
Candle Standards: The earliest attempts to standardize light measurement began in the 1800s with the "standard candle" made from specific materials like spermaceti (whale oil). Different countries developed their own standards—the English candlepower was based on a spermaceti candle burning at a rate of 120 grains per hour, while Germany used the Hefnerkerze, based on a specific lamp design.
-
The Violle: In 1884, French physicist Jules Violle proposed a more scientific standard based on the light emitted by one square centimeter of platinum at its melting point. This unit, called the "violle," was approximately equal to 60 English candlepower and represented one of the first attempts to create a reproducible standard independent of candle composition.
-
The Birth of the Candela: After decades of scientific refinement, the "new candle" was proposed in 1937 and officially adopted in 1948 as the candela. It was initially defined based on a black-body radiator at the temperature of solidifying platinum. This marked the transition to a truly scientific approach to light measurement based on physical principles rather than reference artifacts.
-
Modern Definition: In 1979, due to difficulties in realizing a platinum-based standard, the candela was redefined in terms of radiant power at a specific frequency. The current definition, established in 2019 as part of the SI system revision, defines the candela using fundamental physical constants, creating a stable and universally reproducible standard for light measurement.
-
Photometry Development: The science of photometry evolved alongside these standards, with the development of instruments like Bunsen's grease-spot photometer in the 1840s and later the Lummer-Brodhun photometer in the 1880s. These tools allowed for practical comparison of light sources and paved the way for modern digital light meters and spectrophotometers.
-
Illumination Standards: As electric lighting became widespread in the 20th century, standards for workplace and public space illumination developed. The first formal recommendations for lighting levels were published in the 1930s, evolving into today's comprehensive standards that specify appropriate illuminance for everything from operating rooms to museum displays.
Light Intensity in Our World
- Direct sunlight on a clear day delivers approximately 100,000 lux to Earth's surface — over 200 times brighter than a well-lit office space, which typically maintains 400-500 lux.
- A full moon on a clear night provides only about 0.1-0.3 lux of illumination — yet this is sufficient for the human eye's rod cells to perceive shapes and movement, demonstrating our remarkable visual adaptation to different light levels.
- The human eye can perceive light over an extraordinary range of intensities, from the 0.000001 lux detectable after complete dark adaptation to direct sunlight that is 10 billion times brighter, representing one of the widest dynamic ranges of any sensing system.
- Modern LED headlights can emit over 100,000 candelas when on high beam, tightly focusing their light to illuminate objects hundreds of meters ahead while using just 25-60 watts of power — demonstrating the remarkable efficiency of focused light sources.
- Properly designed lighting for hospital operating rooms must provide 1,000-2,000 lux of shadow-free illumination — ten times that of a typical living room — to ensure surgeons can perform precise procedures safely.
Categories
Light Intensity Unit Converter
1 Candela (cd) = 12.57 Lumen (lm)
Light Intensity Units
From architectural design to photography — light intensity units illuminate our understanding of how we perceive brightness, enabling scientists, engineers, and designers to create environments that are both functional and visually pleasing.
Common Light Intensity Units
Different aspects of light measurement use specialized units to quantify brightness, illumination, and light output:
Luminous Intensity and Flux Units
- Candela (cd): The SI base unit of luminous intensity, measuring the brightness of a light source in a specific direction. One candela approximates the light intensity of a common candle. Used to measure focused light sources like spotlights and LEDs.
- Lumen (lm): The SI unit of luminous flux, measuring the total amount of visible light emitted by a source in all directions. A standard 60W incandescent bulb produces about 800 lumens. Commonly used on light bulb packaging to indicate brightness.
- Candlepower (cp): A historical unit of luminous intensity that predates the candela, based on the light produced by a standard candle. While largely replaced by the candela in scientific contexts, it still appears in some lighting specifications.
- Millicandela (mcd): Equal to 1/1000 of a candela, frequently used for measuring the intensity of LEDs and small display lights in electronic devices where precise low-level light measurement is needed.
Illuminance Units
- Lux (lx): The SI unit of illuminance, measuring the amount of light that falls on a surface. One lux equals one lumen per square meter. Used in architectural lighting, workplace safety standards, and photography to ensure proper lighting levels.
- Foot-candle (fc): The imperial unit of illuminance, equal to one lumen per square foot or approximately 10.76 lux. Still commonly used in North America for lighting specifications in construction and theatrical lighting design.
- Phot (ph): An older CGS unit of illuminance equal to 10,000 lux (one lumen per square centimeter). Rarely used today except in some specialized scientific literature and historical contexts.
- Nox: A unit representing very low levels of illuminance (0.001 lux), sometimes used in astronomy and night vision applications to quantify the minimum light levels detectable by the human eye.
History of Light Measurement
Our journey to quantify and standardize light measurement reflects humanity's enduring relationship with illumination:
-
Candle Standards: The earliest attempts to standardize light measurement began in the 1800s with the "standard candle" made from specific materials like spermaceti (whale oil). Different countries developed their own standards—the English candlepower was based on a spermaceti candle burning at a rate of 120 grains per hour, while Germany used the Hefnerkerze, based on a specific lamp design.
-
The Violle: In 1884, French physicist Jules Violle proposed a more scientific standard based on the light emitted by one square centimeter of platinum at its melting point. This unit, called the "violle," was approximately equal to 60 English candlepower and represented one of the first attempts to create a reproducible standard independent of candle composition.
-
The Birth of the Candela: After decades of scientific refinement, the "new candle" was proposed in 1937 and officially adopted in 1948 as the candela. It was initially defined based on a black-body radiator at the temperature of solidifying platinum. This marked the transition to a truly scientific approach to light measurement based on physical principles rather than reference artifacts.
-
Modern Definition: In 1979, due to difficulties in realizing a platinum-based standard, the candela was redefined in terms of radiant power at a specific frequency. The current definition, established in 2019 as part of the SI system revision, defines the candela using fundamental physical constants, creating a stable and universally reproducible standard for light measurement.
-
Photometry Development: The science of photometry evolved alongside these standards, with the development of instruments like Bunsen's grease-spot photometer in the 1840s and later the Lummer-Brodhun photometer in the 1880s. These tools allowed for practical comparison of light sources and paved the way for modern digital light meters and spectrophotometers.
-
Illumination Standards: As electric lighting became widespread in the 20th century, standards for workplace and public space illumination developed. The first formal recommendations for lighting levels were published in the 1930s, evolving into today's comprehensive standards that specify appropriate illuminance for everything from operating rooms to museum displays.
Light Intensity in Our World
- Direct sunlight on a clear day delivers approximately 100,000 lux to Earth's surface — over 200 times brighter than a well-lit office space, which typically maintains 400-500 lux.
- A full moon on a clear night provides only about 0.1-0.3 lux of illumination — yet this is sufficient for the human eye's rod cells to perceive shapes and movement, demonstrating our remarkable visual adaptation to different light levels.
- The human eye can perceive light over an extraordinary range of intensities, from the 0.000001 lux detectable after complete dark adaptation to direct sunlight that is 10 billion times brighter, representing one of the widest dynamic ranges of any sensing system.
- Modern LED headlights can emit over 100,000 candelas when on high beam, tightly focusing their light to illuminate objects hundreds of meters ahead while using just 25-60 watts of power — demonstrating the remarkable efficiency of focused light sources.
- Properly designed lighting for hospital operating rooms must provide 1,000-2,000 lux of shadow-free illumination — ten times that of a typical living room — to ensure surgeons can perform precise procedures safely.