average illuminance (over a surface) [Eav, ]
illuminance averaged over the specified surface
Unit: lx = lm·m-2
NOTE 1 In practice, this may be approximated by an average of the illuminance at a representative number of points on the surface. The number and positions of these points should be specified in the relevant application guide.
NOTE 2 The specification must include a clear indication of the type of illuminance at the points of the surface, i.e. horizontal, vertical, spherical, cylindrical or semi-cylindrical.