Light Illuminance Calculator
0° for perpendicular light, up to 89° for grazing light.
Understanding Light Illuminance
Understanding how much light reaches a surface is crucial in many fields, from interior design and photography to horticulture and safety. Our Light Illuminance Calculator helps you determine the illuminance (measured in Lux) on a surface based on the light source's intensity, its distance from the surface, and the angle at which the light strikes.
What is Illuminance?
Illuminance is a measure of how much luminous flux (light power) is spread over a given area. In simpler terms, it quantifies how brightly a surface is illuminated. The standard unit for illuminance is the Lux (lx), which is equivalent to one lumen per square meter (lm/m²).
Key Factors Affecting Illuminance:
- Luminous Intensity (Candela, cd): This is a measure of the light source's power in a particular direction. A higher candela value means a brighter light source. Think of it as the "strength" of the light emitted.
- Distance from Source (Meters, m): Light follows the inverse square law. This means that as the distance from a point light source doubles, the illuminance on a surface decreases by a factor of four. The further away you are, the dimmer the light appears.
- Angle of Incidence (Degrees, °): If light strikes a surface perpendicularly (at 0 degrees relative to the surface normal), it provides maximum illuminance. As the angle increases (meaning the light hits the surface more obliquely), the same amount of light is spread over a larger area, reducing the illuminance. This is why the sun feels less intense in the early morning or late afternoon compared to midday.
How the Calculator Works:
Our calculator uses the following formula to determine illuminance:
Illuminance (E) = (Luminous Intensity (I) / Distance (d)²) * cos(θ)
Where:
Eis Illuminance in Lux (lx)Iis Luminous Intensity in Candela (cd)dis Distance in meters (m)θis the Angle of Incidence in degrees (0° for perpendicular light, up to 90° for grazing light).
Practical Applications:
This calculator is useful for various applications:
- Interior Lighting Design: Ensure adequate lighting levels for tasks in offices, homes, or workshops.
- Photography: Calculate light levels for proper exposure.
- Horticulture: Determine if plants are receiving sufficient light for growth.
- Safety Standards: Verify that emergency exits or work areas meet minimum illuminance requirements.
Use the calculator above to explore how these factors influence the light levels on your surfaces.
Realistic Examples:
- Typical Office Lighting: Around 300-500 Lux
- Bright Daylight (indoors, near window): 1000-2000 Lux
- Full Daylight (outdoors): 10,000-25,000 Lux
- Moonlight: Less than 1 Lux
For instance, if you have a spotlight with a luminous intensity of 1000 cd, placed 2 meters away and shining perpendicularly (0° angle), the illuminance would be 250 Lux. If you move it to 5 meters away at a 45° angle, the illuminance drops significantly to about 28.3 Lux.