Useful Formulas
- Calculating Light Level At A Point

E = I/Dsquared x (cosÐq) x LLF

E = Illumination on the surface

I = Luminous Intensity (candlepower)

D = Distance

cosÐq = surface orientation (aka angle theta)

LLF - Light Lost Factor

Figure 1. Calculating light level at a point. Calculating light level at a point rather than average light level over a space is best performed using the Point Method. Calculating light level at a point is helpful for, among others, designs for supplementary and outdoor lighting. The formulas are based on the candlepower of the light source in candelas and use the inverse square law as a building block