quotient of the illuminance at a point on a given plane due to the light received directly and indirectly from a sky of assumed or known luminance distribution and the illuminance on a horizontal plane due to an unobstructed hemisphere of this sky, where the contribution of direct sunlight to both illuminances is excluded
Note 1 to entry: Glazing, dirt effects, etc. are included.
Note 2 to entry: When calculating the lighting of interiors, the contribution of direct sunlight has to be considered separately.
Note 3 to entry: The daylight factor has unit one.
Note 4 to entry: This entry was numbered 845-09-97 in IEC 60050-845:1987.
Note 5 to entry: This entry was numbered 17-279 in CIE S 017:2011.