When measuring the brightness of light sources, terms like lumens, candela, and Lux are often used. However, understanding the differences between lumen vs candela vs lux can be confusing.
Lumens measure the total amount of visible light emitted by a source, while candela measures the intensity of light in a specific direction. Lux, however, quantifies the amount of light that falls on a surface per unit area.
So, this article will explore the distinctions between these units and help you determine the best suited for your lighting needs.
What is Lumen?
Lumen is a unit of measurement used to quantify the total amount of visible light emitted by a light source. In simpler terms, it tells us how bright a light bulb or fixture appears to the human eye.
The higher the lumen value, the brighter the light source. For example, a light bulb with a higher lumen rating will produce more light and illuminate a larger area compared to a bulb with a lower lumen rating.
Lumen is particularly useful when comparing different types of light bulbs or fixtures to determine which will provide the desired brightness level.
What is Candela?
Candela is a unit of measurement that quantifies the intensity of light emitted by a source in a specific direction. It measures how bright a light appears to the human eye when viewed from a particular angle.
Candela focuses on the concentration of light in a specific direction. For example, a flashlight with a high candela rating will produce a more intense beam of light that can reach farther distances than a flashlight with a lower candela rating.
Candela is particularly useful for applications where the directionality and focus of light are essential, such as spotlights, headlights, and searchlights.
What is Lux?
Lux is a unit of measurement used to quantify the amount of light that falls on a surface per unit area. In simpler terms, it measures the brightness or intensity of light as perceived by the human eye on a given surface.
Lux measures the intensity of light emitted by a source and the distance from the source to the illuminated surface. For example, a reading lamp close to a book may provide a higher lux value than the lamp set farther away, resulting in brighter and more comfortable reading conditions.
Lux is commonly used in lighting design, architecture, and engineering to ensure appropriate illumination levels for various applications and spaces.
Lumen vs Candela vs Lux: What is the Difference?
Lumen, candela, and lux are all units of measurement used to describe different aspects of light. The main difference lies in what each unit measures and how it relates to the perception of brightness:
- Lumen tells us how bright the light appears overall, regardless of its emitted direction or the distance from the source.
- Candela quantifies how bright the light appears when viewed from a particular angle, focusing on the concentration of light in that direction.
- Lux quantifies the brightness or intensity of light as perceived by the human eye on a given surface, taking into account both the intensity of the light source and the distance from the source to the illuminated surface.
Lumen describes the total brightness of a light source, candela describes the intensity of light in a specific direction, and lux represents the brightness of light as it falls on a surface.
Each unit serves a distinct purpose and is used in different contexts to characterize and quantify various aspects of light.
| Property | Lumen | Candela | Lux |
|---|---|---|---|
| Definition | Measures total amount of visible light emitted by a source | Measures intensity of light emitted by a source in a specific direction | Measures amount of light that falls on a surface per unit area |
| Symbol | lm | cd | lx |
| What it measures | Total brightness of a light source | Intensity of light in a specific direction | Brightness of light as it falls on a surface |
| Example | A light bulb may emit 800 lumens | A spotlight may have 2000 candela | A desk may have 500 lux of illumination |
| Application | Choosing light bulbs for homes | Designing spotlights and headlights | Determining lighting levels in buildings |
How Do You Convert Lumens to Candela?
Converting lumens to candela involves considering the angular spread of light emitted by a source. To convert lumens to candela, you need to know the beam angle of the light source.
The formula for converting lumens (lm) to candela (cd) is:
Candela (cd) = Lumens (lm) / (4π × Steradian)
Here, Steradian is a unit of measurement representing the solid angle subtended by a portion of space from the centre of a sphere, and π is the mathematical constant pi (approximately 3.14159).
In practical terms, if you have a light source with a known lumen output and beam angle, you can use this formula to calculate the candela output.
How Do You Convert Lumens to Lux?
Converting lumens to lux involves accounting for the Area where the light is distributed. To convert lumens to lux, you need to know the location area where the light is spread.
The formula for converting lumens (lm) to lux (lx) is:
Lux (lx) = Lumens (lm) / Area (m^2)
Here, Area represents the surface area over which the light is distributed, typically measured in square meters (m^2). To calculate lux, divide the total lumens by the Area in square meters.
In practical terms, if you have a light source with a known lumen output and want to determine the illumination level at a specific surface, you can use this formula.
How Do You Convert Lux to Candela?
Converting lux to candela involves considering the Distance from the light source to the illuminated surface. To convert lux to candela, you need to know the Distance from the light source to the bright surface.
The formula for converting lux (lx) to candela (cd) is:
Candela (cd) = Lux (lx) × (Distance)^2
Here, Distance represents the Distance from the light source to the illuminated surface, typically measured in meters (m). To calculate candela, multiply the lux value by the square of the Distance in meters.
In practical terms, you can use this formula if you have a lux measurement at a specific distance from the light source and want to determine the candela output.
Conclusion
The choice between lumen, candela, and lux depends on the lighting context. Lumen measures overall brightness, which is ideal for selecting light bulbs. Candela assesses intensity in a particular direction, which is crucial for spotlights.
Lux determines brightness on a surface, which is vital for lighting levels indoors. Each unit offers unique insights for different lighting tasks.
