A method for determining a Lighting Preference Index of a test illuminant by (a) providing a spectrum of light emitted by the composite light source as a Spectral Power Distribution, preferably having a precision of 1-2 nm, preferably finer; (b) determining a color point from the SPD of the test illuminant, said color point comprising color temperature and a Duv, said Duv being a distance of the color point from a Planckian locus in a u-v chromaticity space; (c) calculating a Whiteness component from the Duv according to Whiteness = 1 - 100 Duv + 0.010 2; (c') determining a reference spectrum from a color temperature of the test illuminant; (d') calculating color points of all 1600 Munsell colors in CIELAB color space for both a reference illuminant and the test illuminant; (e') calculating color rendition vectors (CRVs) for the test illuminant, relative to the reference spectrum, said CRVs being a representation of a magnitude and direction of a color appearance shift with respect to the reference illuminant; (f) calculating a Net Saturation Value according to NSV = ∑ i = 1 10 NSV i / 10, wherein NSV i = (percent of CRVs in hue i with 2.3 < Δ C ab < 15) - (percent of CRVs in hue i with Δ C ab < -2.3); where ΔC ab is a radial component of the CRV and represents a shift in perceived chroma, or saturation, and i represents a hue category from the 10 main hue categories of the Munsell system; and a Hue Distortion Value according to HDV = ∑ i = 1 10 HDV i / 10, wherein HDV i = percent of CRVs in hue i with Δ h ab > π 20 × Δ h ab, avg, i π / 20, where Δh ab is an azimuthal component of the CRV and represents a shift in perceived hue, i represents the hue category for the 10 main hue categories of the Munsell system, and Δ h ab,avg,i is an average Δh ab value for all colors within hue i; (g') calculating a Color Appearance component according to Color Appearance = ( NSV - HDV /2.5)/50; and (d) merging the Whiteness component from step (c) and the Color Appearance component from step (g') into the LPI according to LPI = 100 + 50 × [0.38 × Whiteness + 0.62 × Color Appearance]. (a) providing a spectrum of light emitted by the composite light source as a Spectral Power Distribution, preferably having a precision of 1-2 nm, preferably finer; (b) determining a color point from the SPD of the test illuminant, said color point comprising color temperature and a Duv, said Duv being a distance of the color point from a Planckian locus in a u-v chromaticity space; (c) calculating a Whiteness component from the Duv according to Whiteness = 1 - 100 Duv + 0.010 2; (c') determining a reference spectrum from a color temperature of the test illuminant; (d') calculating color points of all 1600 Munsell colors in CIELAB color space for both a reference illuminant and the test illuminant; (e') calculating color rendition vectors (CRVs) for the test illuminant, relative to the reference spectrum, said CRVs being a representation of a magnitude and direction of a color appearance shift with respect to the reference illuminant; (f) calculating a Net Saturation Value according to NSV = ∑ i = 1 10 NSV i / 10, wherein NSV i = (percent of CRVs in hue i with 2.3 < Δ C ab < 15) - (percent of CRVs in hue i with Δ C ab < -2.3); where ΔC ab is a radial component of the CRV and represents a shift in perceived chroma, or saturation, and i represents a hue category from the 10 main hue categories of the Munsell system; and a Hue Distortion Value according to HDV = ∑ i = 1 10 HDV i / 10, wherein HDV i = percent of CRVs in hue i with Δ h ab > π 20 × Δ h ab, avg, i π / 20, where Δh ab is an azimuthal component of the CRV and represents a shift in perceived hue, i represents the hue category for the 10 main hue categories of the Munsell system, and Δ h ab,avg,i is an average Δh ab value for all colors within hue i; a Net Saturation Value according to NSV = ∑ i = 1 10 NSV i / 10, wherein NSV i = (percent of CRVs in hue i with 2.3 < Δ C ab < 15) - (percent of CRVs in hue i with Δ C ab < -2.3); where ΔC ab is a radial component of the CRV and represents a shift in perceived chroma, or saturation, and i represents a hue category from the 10 main hue categories of the Munsell system; and a Hue Distortion Value according to HDV = ∑ i = 1 10 HDV i / 10, wherein HDV i = percent of CRVs in hue i with Δ h ab > π 20 × Δ h ab, avg, i π / 20, where Δh ab is an azimuthal component of the CRV and represents a shift in perceived hue, i represents the hue category for the 10 main hue categories of the Munsell system, and Δ h ab,avg,i is an average Δh ab value for all colors within hue i; (g') calculating a Color Appearance component according to Color Appearance = ( NSV - HDV /2.5)/50; and (d) merging the Whiteness component from step (c) and the Color Appearance component from step (g') into the LPI according to LPI = 100 + 50 × [0.38 × Whiteness + 0.62 × Color Appearance].