🕯️ Directional Photometry & Beam Optics
Luminous Intensity Unit Converter
Convert directional luminous intensity ($I_v = d\Phi/d\Omega$) across Candelas ($\text{cd}$), Millicandelas ($\text{mcd}$), Candlepower ($\text{cp}$), and $\text{Hefnerkerze}$.
🕯️ Wax Candle (1 cd)
💡 5mm LED (2,500 mcd)
🔦 Spotlight (25k cd)
🗼 Lighthouse Beacon (1M cd)
Input Intensity Value
Standard Candela (cd)
1.000 cd
Millicandela
1,000 mcd
Candlepower
1.019 cp
Hefnerkerze
1.107 HK
💡 Luminous Intensity Equivalence:
$$1\text{ Candela (cd)} = 1,000\text{ mcd} = 1\text{ Lumen / steradian} \approx 1.019\text{ Candlepower}$$
Understanding Luminous Intensity ($I_v$)
Luminous intensity ($I_v$) is the base SI unit of photometry, measuring the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle:
- Definition: $$I_v = \frac{d\Phi_v}{d\Omega} \text{ (in Lumens/steradian = Candelas)}$$
- SI Base Unit: The Candela ($\text{cd}$) is one of the seven base SI units, officially defined by monochromatic radiation of frequency $540 \times 10^{12}\text{ Hz}$ at $1/683\text{ W/sr}$.
- Beam Angle Concentration: A narrow spotlight focusing 100 lumens into a tight $10^\circ$ beam produces significantly higher peak Candelas than a wide floodlight.