💡 Photometry & Lighting Design
Illuminance (Lux vs Foot-Candle) Converter
Convert surface lighting illuminance ($E_v = \Phi_v/A$) across $\text{Lux}$ ($\text{lx} = \text{lm/m}^2$), $\text{Foot-candles}$ ($\text{fc} = \text{lm/ft}^2$), $\text{Phots}$ ($\text{ph}$), and $\text{Nox}$.
☀️ Direct Sun (100k lx)
⛅ Overcast Sky (1,000 lx)
🏢 Office Desk (500 lx)
🛋️ Living Room (150 lx)
🌕 Full Moon (0.25 lx)
Input Illuminance
Standard Foot-candles (fc)
46.45 fc
Lux (lx)
500.0 lx
Phot (ph)
0.0500 ph
Nox (millilux)
500,000 nox
💡 Illuminance Equivalence:
$$1\text{ Foot-candle (fc)} = 10.7639\text{ Lux (lx)} \implies 1\text{ Phot (ph)} = 10,000\text{ Lux}$$
Understanding Illuminance ($E_v$)
Illuminance ($E_v$) is the total luminous flux incident on a surface per unit area, weighted by the human eye photopic sensitivity function $V(\lambda)$:
- Definition: $$E_v = \frac{d\Phi_v}{dA}$$
- Inverse Square Law of Lighting: $$E_v = \frac{I_v}{d^2} \cos\theta$$ ($I_v = \text{luminous intensity in Candelas}$, $d = \text{distance}$).
- Conversion Factor: $1\text{ Foot-candle} = 1\text{ lm/ft}^2 = 10.7639104\text{ Lux}$.