Illumination Measurement Converter
Convert between different units of illuminance instantly. Essential for lighting design, photography, and optical engineering applications.
Conversion Formulas (1 lux equivalents):
1 lx = 1 lm/m² = 1 cd·sr/m² = 0.0001 ph = 0.092903 fc = 0.092903 lm/ft² = 0.00064516 lm/in² = 0.0001 lm/cm² = 0.092903 cd·sr/ft²
Key Relationships: 1 ph = 10,000 lx | 1 fc = 10.76391 lx | 1 lm/in² = 1,550.0031 lx
About This Illumination Converter
Our Illumination Measurement Converter is a specialized tool designed for lighting engineers, photographers, architects, and professionals working with light measurement. Illuminance, measured in lux (lx), represents the amount of luminous flux per unit area and is crucial in lighting design, photography exposure calculations, and workplace lighting standards.
The converter handles all common illuminance units, with precise conversions between metric (lux, phot) and imperial (foot-candle) systems, as well as various lumen-based and candela-based expressions. It's particularly valuable for translating between different measurement systems used in international standards and technical specifications.
Key Features
Comprehensive Unit Coverage
Convert between all major illuminance units including lux, phot, foot-candle, and various lumen-based and candela-based units used across different industries.
Scientific Precision
Maintain accuracy across different measurement systems, from high-illuminance (phots) to low-illuminance (foot-candles) applications.
Photometry Support
Includes both photometric (lux, phot) and radiometric (lumen-based) expressions of illuminance for comprehensive light measurement.
International Standards
Aligned with scientific conventions and engineering practices worldwide, supporting both metric and imperial measurement systems.
Why Choose Our Converter?
- Accuracy: Uses exact conversion factors for precise photometric calculations
- Dual Systems: Supports both metric (SI) and imperial (US customary) units
- Range Flexibility: Easily switch between high and low illuminance units
- Multiple Expressions: Converts between lux, lumens, and candela-based units
- Responsive Design: Works perfectly on both desktop and mobile devices
Frequently Asked Questions
What is illuminance and how does it differ from luminance?
Illuminance measures how much luminous flux (light) is incident on a surface per unit area (measured in lux or foot-candles), while luminance measures how much light is emitted or reflected from a surface in a particular direction (measured in candela per square meter or nits). Illuminance is about light falling on a surface (incident light), whereas luminance is about light coming from a surface (emitted or reflected light). For example, illuminance would measure how much light hits your desk, while luminance would measure how bright your computer screen appears.
When would I use foot-candles versus lux?
Foot-candles (fc) are commonly used in the United States for architectural lighting design, while lux (lx) is the international standard (SI unit) used in most other countries. 1 foot-candle equals approximately 10.764 lux. While the lighting industry in the U.S. primarily uses foot-candles, scientific and international projects typically use lux. This converter makes it easy to switch between these units when working with international standards or collaborating across regions.
What are typical illuminance values for common situations?
Illuminance values vary widely:
• Direct sunlight: 32,000-100,000 lx
• Overcast daylight: 1,000-10,000 lx
• Office lighting: 300-500 lx
• Home lighting: 100-300 lx
• Street lighting: 5-30 lx
• Full moon: ~0.25 lx
• Moonless night: ~0.001 lx
Photographic light meters often measure in lux or foot-candles, with typical exposure values ranging from about 10 lx (dim interior) to 100,000 lx (bright sunlight).
Why are there so many different units for measuring light?
The variety of light measurement units exists because of historical development, different measurement systems (metric vs. imperial), and the need to measure different aspects of light. The phot (ph) comes from the older CGS system, while lux is from the modern SI system. Foot-candles persist in the U.S. due to customary units. Lumen-based units relate to total luminous flux, while candela-based units relate to luminous intensity. Each unit has specific applications where it's most convenient - for example, phots for very high illuminance (like in scientific instruments), lux for general use, and foot-candles for architectural applications in the U.S.
How does illuminance relate to exposure in photography?
In photography, illuminance (measured in lux or foot-candles) directly affects exposure. The exposure value (EV) system is based on illuminance levels, with each EV representing a doubling or halving of light. Typical conversions:
• EV 15 = 32,768 lx (bright sunlight)
• EV 12 = 4,096 lx (cloudy bright)
• EV 9 = 512 lx (overcast)
• EV 6 = 64 lx (indoor lighting)
• EV 3 = 8 lx (dim interior)
Photographers often use light meters that measure in lux or foot-candles to determine proper camera settings for a given lighting condition. This converter helps translate between different light measurement units used in photography equipment and standards.