To understand the luminescen t properties of the prepared material, CIE 1931 chromaticity coordinates are also calculated
from the emission spectrum. The CIE system characterizes the colors by a two color coordinates x and y which specify the point on the chromaticity diagram. This system offers more precision in color measure ment because the parameters are based on the spectral power distribut ion (SPD) of the light emitted from a colored object and are factored by sensitivity curves which have been measure d for the human eye