Luminance Converter
Convert luminance units — cd/m² (nits), foot-lamberts, stilb, and more. Free online luminance converter for display technology, photography, and lighting design.
Understanding Luminance
Luminance measures the brightness of a surface as perceived by the human eye. You express luminance in candelas per square meter (cd/m²), also called nits. This photometric quantity describes light emitted, reflected, or transmitted from a surface.
Luminance differs from illuminance. Illuminance measures light falling on a surface. Luminance measures light leaving a surface. Your eyes respond to luminance, not illuminance.
Luminance Formulas
L = I / A
Definition: Luminance equals luminous intensity divided by projected area. Units are cd/m² or nits.
L = E × ρ / π
Reflecting surface: Luminance equals illuminance times reflectance divided by pi for Lambertian surfaces.
L = Φ / (A × Ω)
Extended source: Luminance equals luminous flux divided by area times solid angle.
Example: A display producing 300 cd intensity over 0.1 m² area has L = 300 / 0.1 = 3,000 cd/m² or 3,000 nits.
Common Luminance Conversions
| cd/m² (nits) | cd/ft² | Foot-lamberts (fL) |
|---|---|---|
| 0.2919 | 1 | 1 |
| 1 | 0.0929 | 0.2919 |
| 3.426 | 0.3183 | 1 |
| 10 | 0.929 | 2.919 |
| 100 | 9.29 | 29.19 |
| 1,000 | 92.9 | 291.9 |
Display Luminance Reference
| Display Type | Typical Luminance (nits) |
|---|---|
| Indoor SDR Monitor | 200-300 |
| HDR Monitor | 400-1,000 |
| Smartphone | 500-1,500 |
| Outdoor Display | 2,000-5,000 |
| Cinema Screen | 48-108 |
| Clear Sky | 2,000-8,000 |
Practical Applications
Display Calibration
Professional displays calibrate to 100-120 cd/m² for color grading. HDR content requires higher peak luminance. Calibration ensures accurate color reproduction.
Roadway Lighting
Road surface luminance determines visibility. Standards specify 0.5-2 cd/m² for different road classes. Uniformity ratios ensure consistent visibility.
Photography and Cinematography
Light meters measure scene luminance. Incident meters measure illuminance. Understanding both ensures proper exposure settings.
Workplace Lighting
Office tasks require specific luminance ratios. Display-to-surround ratio should be 3:1 to 10:1. Excessive contrast causes eye strain.
Frequently Asked Questions
What is the difference between nits and lumens?
Nits measure luminance (brightness per area). Lumens measure total luminous flux. A projector might output 3,000 lumens but produce 100 nits on a screen.
What is a foot-lambert?
Foot-lambert is the Imperial unit of luminance. One foot-lambert equals 3.426 cd/m². Cinema screens traditionally specify luminance in foot-lamberts.
How bright should a TV be?
For dark rooms, 100-150 nits works well. Bright rooms need 300-500 nits. HDR content benefits from 600+ nits peak brightness.
How do you measure luminance?
Use a luminance meter or spot photometer. These instruments measure cd/m² from a specific viewing angle. Camera-based systems map luminance across scenes.
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