Measurement

Hi Keith, The reference guide gives specifics about time of year and time of day for Option 1: Simulation. Typically one would be using a computer program to create a daylight simulation. The modeling input would use sun angle data in regards to the specifics for time of year and day. It doesn't matter if it is actually cloudy outside as the simulation is a computer model. Option3: Measurement, involves taking live measurements with a light meter and does not require a specific time of day or time of the year.