Hemispherical Illuminance

This page describes how Hemispherical Illuminance is calculated.

On the following example, the source is simulated by a local point source.

Note: The source can also be an extended light source like luminaire, ambient, surface source, etc.

The sensor is sensible to light incoming from all directions except the direction exactly opposed to the integration direction.

The hemispherical illuminance is an addition of horizontal and radial illuminance.

  • The integration direction is perpendicular to the sensor plane.
  • The integration direction is the same as horizontal illuminance (perpendicular to the horizontal plan).
  • The formula is