Luminous intensity is a measure of the amount of light emitted in a specific direction by a light source. It is measured in candelas (cd) , a unit that indicates how much light is emitted in a specific direction. This is a different way of looking at lighting than light output (lumens) , which measures the total amount of light emitted by a lamp in all directions.
Difference between light intensity and light output:
- Luminous intensity (candela) : Measures the intensity of light in a specific direction. It indicates how bright a light source is when you look directly at it. This is important for directional lighting, such as spotlights or car headlights.
- Light output (lumens) : Measures the total amount of light a light source emits in all directions. This is important for the overall brightness of a room.
Example:
- A spotlight has a high light output because the light is focused in a specific direction, while the light output can be relatively low because the light only illuminates a small area.
- A pendant lamp that illuminates the room in all directions has a high light output, but the light intensity is distributed throughout the room.
Application of luminous intensity:
Light intensity is especially important in applications where the light beam needs to be focused on a specific point, such as:
- Car headlights : Where the light intensity (candela) is important to see how far the headlights shine.
- Spotlights and projectors : These often have a high light output, focused on a small area, so that the light is displayed intensely.
- Flashlights : The brightness determines how bright the beam is and how far you can see.
Summary:
Luminous intensity, measured in candelas (cd) , indicates the intensity of light in a given direction. This is useful for measuring directional lighting, such as spotlights, while light output (lumens) measures the total amount of light emitted by a light source.