luminous intensity converter
Convert luminous intensity across Candela (cd), Millicandela, Hefnerkerze, and Carcel. Features interactive Candela to Lumens Beam Bridge, ANSI/NEMA FL-1 throw estimator, dynamic 2D beam ray simulation, and optics spec export.
Unit ConvertersPhotometric Omni-Grid
Bidirectional multi-unit luminous intensity matrix with instantaneous synchronization
SI base unit of luminous intensity (1 lumen per steradian)
Standard measurement for raw SMD LEDs and indicator diodes
Standard unit for automotive headlights, beacons and spotlights
Historical standard based on the amyl acetate lamp (~0.90 cd)
Historical standard based on the colza oil burner (~9.74 cd)
Standard carbon-filament reference candlepower (~0.981 cd)
Standard automotive driving beam with intensive central optical throw
The 'Candela to Lumens' Beam Bridge
Calculate total luminous flux in Lumens (Φ) from directional intensity (I) and conical beam angle
Angle between points where intensity drops to 50% of maximum (FWHM)
Photonic 2D Beam Ray Engine
Dynamic ray tracing simulation showing aperture spread and optical core brightness
ANSI/NEMA FL-1 Beam Distance Estimator
Optical throw distance evaluated down to 0.25 lux (equivalent to full moonlight at zenith)
| Distance | Illuminance (Lux) | Perceptual Lighting Condition |
|---|---|---|
| 1 m (3 ft) | 25,000 lx | Surgical Spotlight (~10,000 lx) |
| 5 m (16 ft) | 1,000 lx | Precision Engineering (~1,000 lx) |
| 10 m (33 ft) | 250 lx | Ambient Living Space (~50 lx) |
| 25 m (82 ft) | 40 lx | Ambient Living Space (~50 lx) |
| 50 m (164 ft) | 10 lx | Moonlight Threshold (0.25 lx) |
| 100 m (328 ft) | 2.50 lx | Moonlight Threshold (0.25 lx) |
| 200 m (656 ft) | 0.63 lx | Moonlight Threshold (0.25 lx) |
How to Use the Luminous Intensity Converter
Step-by-step instructions for converting candela units, bridging intensity to total lumens, and calculating ANSI beam throw distance.
Enter Luminous Intensity (cd)
Input your source intensity into any field of the Photometric Omni-Grid (Candela, Millicandela, Kilocandela, Candlepower, Hefnerkerze, Carcel) or choose an optical preset.
Instant Multi-Unit Conversion
The converter instantly recalculates and synchronizes values across modern SI standards and legacy historical optical systems without rounding error.
Set Beam Angle & Solid Angle (Ω)
Adjust the beam angle slider (5° pencil spot to 180° hemisphere) to calculate the intercepted solid angle in steradians (sr) and observe the 2D photonic ray tracer.
Bridge Intensity to Total Flux (Lumens)
Evaluate total integrated luminous flux (Φ = I · Ω) to determine how many lumens your light source emits across the full conical beam.
Analyze ANSI Throw & Distance Matrix
Examine the certified ANSI/NEMA FL-1 throw distance (D = 2√I to the 0.25 lux moonlight limit) and check the Inverse-Square Law illuminance table (1 m to 200 m).
Export Optical Specification
Click 'Copy Optics Spec Sheet' to copy a structured technical summary (intensity, beam angle, total lumens, and ANSI throw distance) to your clipboard.
Frequently Asked Questions (FAQ)
Detailed photometric principles covering candela definition, lumens vs. lux, ANSI FL-1 flashlight standards, and the inverse-square law.
Q:What is luminous intensity and how is the Candela (cd) defined in the SI system?
Luminous intensity (I_v) is the photometric measure of the luminous flux emitted by a point source per unit solid angle in a specific direction: I = dΦ / dΩ (measured in Candela, where 1 cd = 1 lm/sr). The candela is one of the seven base SI units. It is defined by fixing the luminous efficacy of monochromatic radiation of frequency 540 × 10¹² Hz (green light at approximately 555 nm wavelength) to exactly 683 lumens per Watt. Unlike total luminous flux (lumens), candela quantifies the directional concentration of a light beam.
Q:What is the difference between Candela (cd), Lumens (lm), and Lux (lx)?
These three photometric quantities describe different aspects of light: Candela (cd) measures directional beam intensity (how concentrated the beam is in one direction); Lumens (lm) measure total luminous flux (the overall amount of light emitted in all directions); and Lux (lx) measures illuminance (the density of light falling on a surface: 1 lx = 1 lm/m²). An analogy: Lumens is the total volume of water sprayed, Candela is the pressure of the nozzle jet, and Lux is how wet a target surface gets at a given distance.
Q:How does the ANSI/NEMA FL-1 standard calculate beam throw distance?
The ANSI/NEMA FL-1 flashlight standard defines beam distance as the distance at which illuminance drops to 0.25 lux (the light level cast by a clear full moon on an open field). Using the Inverse-Square Law E = I / D², setting E = 0.25 lux yields the formula D = √(I / 0.25) = 2 · √I meters. For instance, an automotive high beam rated at 25,000 cd provides an ANSI throw distance of 2 · √25,000 = 316.2 meters (1,037 feet).
Q:How do you calculate total Lumens from Candela and beam angle?
For a uniform rotational conical beam of apex angle θ (in degrees), the solid angle subtended is Ω = 2π · (1 - cos(θ / 2)) steradians. The total luminous flux is then Φ = I · Ω lumens. A narrow 10° spot subtends only 0.0239 sr, so a 10,000 cd beam requires only ~239 lumens. Conversely, a wide 120° floodlight subtends π ≈ 3.14 sr, requiring ~31,416 lumens to achieve that same 10,000 cd center-beam intensity.
Q:How does the Inverse-Square Law govern light falloff with distance?
The Inverse-Square Law states that illuminance on a surface perpendicular to a point light source decreases with the square of the distance: E = I / D². Doubling the distance reduces illuminance to 1/4 (25%), and tripling the distance reduces it to 1/9 (11.1%). This quadratic attenuation explains why long-range lighting (searchlights, automotive driving beams, lighthouses) requires immense candela ratings (10⁴ to 10⁶ cd) to maintain functional illumination at long distances.
Q:How do historical units (Candlepower, Hefnerkerze, Carcel) compare to the modern Candela?
Before modern radiometric definitions, luminous intensity relied on standardized physical burning flames: Candlepower (CP / international candle) was based on sperm whale spermaceti candles (1 CP ≈ 0.981 cd). The Hefnerkerze (HK), created in Germany in 1884, burned amyl acetate in a brass lamp (1 HK = 0.90 cd). The French Carcel burned colza oil (1 Carcel ≈ 9,74 cd). In 1948, the General Conference on Weights and Measures standardized the 'new candle' based on blackbody platinum freezing, later officially named the Candela.
- I: Luminous intensity in Candelas (cd).
- Φ: Total luminous flux in Lumens (lm).
- Ω (Omega): Conical solid angle in Steradians (sr = 2π(1 - cos(θ / 2))).
- θ (Theta): Full conical beam apex angle in degrees (°).
- D: ANSI/NEMA FL-1 beam throw distance in meters to 0.25 lux.
Luminous intensity converter Table
| Unit | candela (cd) | kilocandela | millicandela | candlepower (CP) |
|---|---|---|---|---|
| 1 candela (cd) | 1 | 0.001 | 1,000 | 1.0193679918 |
| 1 kilocandela | 1,000 | 1 | 1,000,000 | 1,019.3679918451 |
| 1 millicandela | 0.001 | 0.000001 | 1 | 0.001019368 |
| 1 candlepower (CP) | 0.981 | 0.000981 | 981 | 1 |
What is luminous intensity converter?
| Interface Element | Optical Function | Practical Application |
|---|---|---|
| Photometric Omni-Grid | Base Conversion | Translates raw intensity values seamlessly between modern SI units and legacy standards. |
| Candela to Lumens Beam Bridge | Flux Calculation | Derives the total light output (Lumens) based on the directional intensity and the specific emission angle. |
| ANSI/NEMA FL-1 Estimator | Throw Distance | Computes the maximum distance at which the light beam will produce 0.25 lux of illumination. |
| Photonic 2D Beam Ray Engine | Visual Simulation | Renders a graphical cross-section of the light cone to evaluate spatial distribution. |