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downward flux, <of a light source>
cumulative flux for the solid angle 2π sr, below the horizontal plane passing through the light source
Note 1 to entry: The downward flux is expressed in lumen (lm).
Note 2 to entry: This entry was numbered 845-09-34 in IEC 60050-845:1987.
Note 3 to entry: This entry was numbered 17-350 in CIE S 017:2011.