Lux to Candela Calculator

Understanding Lux to Candela Conversion

Converting between lux and candela is essential for lighting professionals, engineers, and anyone working with light measurements. While lux measures illuminance (light falling on a surface), candela measures luminous intensity (light emitted by a source). Understanding this conversion helps in proper lighting design and analysis.

What is Lux?

Lux (lx) is the SI unit of illuminance, representing the amount of light falling on a surface. One lux equals one lumen per square meter (lm/m²). It measures how much light reaches a specific area, making it crucial for determining if an area is adequately lit for its intended purpose.

What is Candela?

Candela (cd) is the SI base unit of luminous intensity, representing the amount of light emitted by a source in a particular direction. It measures the brightness of a light source as perceived by the human eye, taking into account the sensitivity of the eye to different wavelengths.

The Conversion Formula

The relationship between lux and candela depends on the distance from the light source. The formula is:

Candela = Lux × Distance²

Where:

Candela (cd) - Luminous intensity
Lux (lx) - Illuminance
Distance (m) - Distance from light source in meters

Practical Applications

This conversion is commonly used in:

Lighting Design: Calculating the required luminous intensity for proper illumination
Photography: Understanding light source characteristics for proper exposure
Architecture: Ensuring adequate lighting levels in buildings
Automotive: Designing headlight systems with proper intensity
Industrial Applications: Setting up work area lighting for safety and productivity

Example Calculation

If you have a light source that produces 100 lux at a distance of 2 meters, the luminous intensity would be:

Candela = 100 lux × (2 m)² = 100 × 4 = 400 cd

Important Considerations

The distance must be measured in meters for accurate results
This formula assumes a point light source and uniform distribution
Real-world applications may require additional factors like beam angle and efficiency
Lux measurements are affected by surface reflectivity and ambient light

Frequently Asked Questions

Why do I need to know the distance for lux to candela conversion?

Distance is crucial because illuminance (lux) decreases with the square of distance from a point light source. The same light source will produce different lux readings at different distances, but its luminous intensity (candela) remains constant. The distance allows us to calculate the actual intensity of the light source.

Can I use this calculator for LED lights?

Yes, this calculator works for LED lights as well as other light sources. However, keep in mind that LED lights often have directional characteristics, and the actual light distribution may not be perfectly uniform. For precise applications, consider the beam angle and light distribution pattern of your specific LED.

What's the difference between lux and lumens?

Lux measures illuminance (light falling on a surface per unit area), while lumens measure luminous flux (total light output from a source). Lux is lumens per square meter. For example, 1000 lumens spread over 10 square meters equals 100 lux.

How accurate is this conversion for real-world applications?

This conversion provides a good approximation for point light sources with uniform distribution. Real-world accuracy depends on factors like light source type, beam angle, surface reflectivity, and ambient lighting conditions. For critical applications, consider consulting lighting professionals or using specialized measurement equipment.

Report Tool or Give Us Suggestions