Luminous Intensity Converter
Convert luminous intensity units — candela, millicandela, candlepower, and more. Accurate online luminous intensity converter for photometry, LED design, and lighting engineering.
Understanding Luminous Intensity
Luminous intensity measures the power of light emitted by a source in a specific direction. You express it in candelas (cd), one of the seven SI base units. One candela equals the luminous intensity of a standard candle.
Luminous intensity differs from luminous flux. Flux measures total light output in all directions. Intensity measures light in a particular direction. LEDs and spotlights specify intensity for beam characterization.
Luminous Intensity Formulas
I = dΦ / dΩ
Definition: Intensity equals luminous flux per unit solid angle. Units are candelas (cd) or lumens per steradian.
E = I / d²
Inverse square law: Illuminance equals intensity divided by distance squared for point sources.
Φ = I × Ω
Total flux: For uniform emission over solid angle, flux equals intensity times solid angle.
Example: An LED producing 0.1 lumens into a 0.1 steradian beam has I = 0.1 / 0.1 = 1 candela intensity.
Common Luminous Intensity Conversions
| Candela (cd) | Millicandela (mcd) | Candlepower (cp) |
|---|---|---|
| 0.001 | 1 | 0.001 |
| 0.01 | 10 | 0.01 |
| 0.1 | 100 | 0.1 |
| 1 | 1,000 | 1 |
| 10 | 10,000 | 10 |
| 100 | 100,000 | 100 |
Light Source Intensity Reference
| Light Source | Intensity (cd) |
|---|---|
| Candle Flame | 1 |
| LED Indicator | 0.1-10 |
| High-Brightness LED | 10-100 |
| Car Headlight (low beam) | 500-1,000 |
| Car Headlight (high beam) | 2,000-5,000 |
| Searchlight | 100,000-1,000,000 |
Practical Applications
LED Selection
LED datasheets specify intensity in millicandelas. Indicator LEDs range 100-5,000 mcd. High-power LEDs reach 10,000+ mcd. Beam angle affects perceived brightness.
Automotive Lighting
Regulations specify minimum and maximum intensity for headlights, taillights, and turn signals. ECE and SAE standards define photometric requirements for vehicle lighting.
Aviation Lighting
Aircraft position lights have specified intensity and color. Runway edge lights use intensity settings for different visibility conditions. Obstruction lights mark tall structures.
Signal and Warning Lights
Emergency vehicles use high-intensity beacons. Intensity requirements ensure visibility in daylight. Flash patterns and color complement intensity for recognition.
Frequently Asked Questions
What is the difference between candela and lumens?
Candela measures intensity in one direction. Lumens measure total output in all directions. A focused spotlight has high candela but moderate lumens.
What is candlepower?
Candlepower is an older term for luminous intensity. One candlepower equals one candela. The term persists in some industries but candela is the official SI unit.
Why do LEDs specify millicandela?
Most indicator LEDs produce less than one candela. Millicandela provides convenient numbers without decimals. A 5,000 mcd LED equals 5 cd.
How does beam angle affect intensity?
Narrower beam angles concentrate flux into smaller solid angles, increasing intensity. Same lumens with half the beam angle produces roughly four times the peak intensity.
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