[9.4.1.1]
The ratio of luminous flux (lumens) calculated as received on the work plane to the total luminous flux (lumens) emitted by the lamps alone. It is equal to the product of room utilization factor and luminaire efficiency.
Note: For luminaires tested with absolute photometry, use Room Utilization Factor (utilance) and luminaire lumens instead of CU and lamp lumens.
NOTE: This definition was changed in ANSI/IES RP-16-17 Addendum 4.
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