The IES Luminaire Classification System (LCS) that defines the distribution of light from a luminaire within three primary solid angles: forward light, backlight and uplight. These are further divided into ten secondary solid angles as described in IES TM-15-11. The BUG rating is then determined using Addendum A for IES TM-15-11 according to a luminaire’s lumen output within the secondary solid angle zones as defined in the document.
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