I. Key Lighting Design Calculations (Practical Formulas) 1. Lumen Method Formula (Determining Fixture Quantity) \[ N = \frac{E \times A}{\varphi \times U \times M} \] N: Number of fixtures E: Target illuminance (lux) A: Area (m²) ϕ: Luminous flux per fixture (lumens, e.g., 24,000 lm for a 200W LED) U: Utilization factor...