Luminance Converter
Enter a luminance value and select a source unit and a target unit to convert between different luminance measurements.
How to Use Our Luminance Converter Tool
Here’s a quick guide to using our free luminance converter for light measurement:
- Enter your luminance value in the first field
- Select the source unit from the dropdown menu (the unit you’re converting from)
- Select the target unit from the second dropdown menu (the unit you want to convert to)
- Click “Convert Luminance”
The tool will instantly display your conversion result, detailed calculation steps, and a comprehensive conversion table showing equivalents in all supported units.
What Is Luminance and Why Does It Matter?
Defining Luminance
Luminance is the measurement of light intensity per unit area that travels in a given direction. In simpler terms, it quantifies how bright a surface appears to the human eye. Unlike illuminance (which measures light falling onto a surface), luminance measures the light emitted, transmitted, or reflected from a surface.
Luminance plays a crucial role in:
- Display technology calibration
- Architectural lighting design
- Visual comfort and ergonomics
- Photography and cinematography
- Safety standards for workplaces and public spaces
The Candela per Square Meter: The Base Unit
The standard SI unit for luminance is the candela per square meter (cd/m²), sometimes called “nits.” This unit serves as the foundation for all luminance measurements and conversions.
For example, a typical office computer monitor might have a luminance of 250-300 cd/m², while HDR displays can reach 1,000 cd/m² or more. Sunlight reflecting off a white surface can exceed 30,000 cd/m².
Understanding Different Luminance Units
SI and Metric Units
The metric system offers several luminance units:
- Candela per square meter (cd/m²): The base SI unit
- Nit (nt): Equivalent to cd/m², often used in display specifications
- Kilocandela per square meter (kcd/m²): Used for very bright sources, 1 kcd/m² = 1,000 cd/m²
- Millicandela per square meter (mcd/m²): Used for dim sources, 1 mcd/m² = 0.001 cd/m²
For example, if your television has a peak brightness of 1,500 nits, this is exactly the same as 1,500 cd/m² or 1.5 kcd/m².
CGS Units
The centimeter-gram-second system includes these historical but still-used units:
- Lambert (L): Approximately 3,183 cd/m²
- Millilambert (mL): 3.183 cd/m²
- Foot-lambert (fL): Approximately 3.426 cd/m²
These units are still commonly used in North American lighting industries and scientific literature. A movie theater screen typically ranges from 14 to 22 foot-lamberts (48 to 75 cd/m²).
Other Specialized Units
Several other units exist for specific applications:
- Apostilb (asb): 0.318 cd/m², historically used in European lighting standards
- Stilb (sb): 10,000 cd/m², used in older scientific papers
- Bril: Approximately 3,183,099 cd/m², rarely used today except in specialized fields
Why Luminance Conversions Matter
Practical Applications
Converting between luminance units is essential in various fields:
- Display Technology: Manufacturers may list specifications in different units (nits, cd/m²)
- International Collaboration: Different regions use different preferred units
- Historical Research: Older documentation often uses obsolete units
- Compliance: Safety standards may specify limits in specific units
Real-World Example
Consider a lighting designer working on an international project. The client specifies that display luminance should be 150 cd/m², but the equipment specifications are in foot-lamberts. Using our converter:
150 cd/m² ≈ 43.78 foot-lamberts
This conversion ensures the correct equipment is selected and installed.
The Mathematics Behind Luminance Conversion
All luminance conversions use a simple formula:
- Convert the input value to the base unit (cd/m²) by multiplying by a conversion factor
- Convert from the base unit to the target unit by dividing by the target unit’s conversion factor
For example, to convert from lamberts to nits:
- 1 lambert = 10,000/π cd/m² ≈ 3,183 cd/m²
- 3,183 cd/m² = 3,183 nits
Our converter handles these calculations automatically while showing you each step.
Common Luminance Values in Everyday Life
Understanding typical luminance values helps provide context:
- Moon on a clear night: 0.25 cd/m²
- Indoor office lighting: 100-300 cd/m²
- Standard computer monitor: 250-350 cd/m²
- HDR television display: 500-1,500 cd/m²
- Outdoor daylight (overcast): 2,000-5,000 cd/m²
- Direct sunlight: 15,000-30,000 cd/m²
FAQ About Luminance and Its Measurement
Q. What’s the difference between luminance and illuminance?
Luminance measures the brightness of a surface as perceived by the human eye (in cd/m²), while illuminance measures the amount of light falling onto a surface (in lux or foot-candles).
Q. Why are there so many different luminance units?
Different luminance units emerged from various scientific traditions (SI, CGS) and specialized applications. Historical uses and regional preferences have kept many of these units in circulation.
Q. How does luminance affect visual comfort?
Too much luminance contrast can cause eye strain and fatigue. Proper luminance ratios between tasks, immediate surroundings, and the general environment are essential for visual comfort. Generally, a 3:1 ratio between task and immediate surroundings is recommended.
Q. How is luminance measured in practice?
Specialized instruments called luminance meters or photometers measure luminance. Modern devices often provide readings in multiple units and can store data for analysis.
Q. Does luminance change with viewing distance?
No, luminance is independent of viewing distance. Unlike illuminance, which decreases with the square of the distance, luminance remains constant regardless of how far away you are from the source.
Conclusion
Understanding luminance and its various measurement units is important for professionals working in lighting, displays, visual ergonomics, and related fields. Whether you’re calibrating a display, designing a workspace, or comparing product specifications, knowing how to convert between units ensures accuracy and consistency.
Our luminance converter tool simplifies these conversions, helping you focus on your project rather than complex calculations. By providing detailed calculation steps and a conversion table, it also serves as an educational resource to deepen your understanding of luminance measurements.
As displays continue to advance and lighting standards evolve, the importance of luminance awareness will only grow. With the knowledge gained from this guide, you’re well-equipped to navigate the world of luminance with confidence.
