Candela (cd) is the unit of luminous intensity in the International System of Units (SI). It measures the intensity of light emitted in a given direction by a light source. The candela is a fundamental unit for describing the luminous intensity of a source, such as a lamp or other light source.
What exactly does candela mean?
- Candela describes the amount of light emitted by a light source in a specific direction. It takes into account the distribution of the light, as opposed to the total amount of light a source emits (which is measured in lumens).
- It specifically focuses on light intensity per unit of space, measured in the direction where the light source emits the most light. In other words, it measures how bright the light is in a particular direction.
Explanation of the unit:
- 1 candela (cd) is the luminous intensity of a light source emitting 1/683 of a watt per steradian in a specific direction at a wavelength of 555 nanometers, which corresponds to the green light to which the human eye is most sensitive.
Example:
- Imagine an LED bulb . If its luminous intensity in a particular direction is 500 cd , this means the bulb emits 500 candelas of light in that direction. The higher the candela number, the brighter the light in that specific direction.
Application:
- Candela is often used in the engineering and lighting industries to specify the luminous intensity of light sources such as lamps, vehicle headlights, flashlights, and other lighting.
- It is also an important measure of the lighting efficiency of light sources, such as when measuring the luminous intensity of floodlights, where the intensity of the light plays a role in how well a particular object or area is illuminated.
Comparison with other light measurements:
- Lumen (lm) measures the total amount of light emitted by a light source, regardless of direction.
- Lux (lx) measures the illumination on a given surface and is equal to 1 lumen per square meter.
- So candela (cd) specifically measures the intensity of light in a particular direction, while lumen and lux are broader measurements of light.
In summary: Candela is the measure of luminous intensity and indicates how brightly a light source shines in a certain direction .