Use the Spectrum Generator tool to generate a spectrum which matches input tristimulus values (i.e. XYZ or L*a*b*) for a given illuminant and Standard Observer. The conversion method used in this tool is based on Principal Component Analysis (PCA). PCA is a mathematical process by which a few spectral components (or base vectors), typically three to six, are extracted from a large number of spectrums forming a reference dataset. The goal of the process is that any spectrum (i.e. color) from the dataset can be obtained by adding the principal components in various proportions, with these proportions derived using the tristimulus values for one or more illuminant. The accuracy of the synthetized spectrum will generally increase as more components are used. The reference dataset used for component extraction is selected to cover a large gamut and is usually representative of a given group of pigments. The principal components of this tool were extracted from measured samples of the NCS, Munsell, and OSA-UCS color order systems. What this means in practice is that, for the same color coordinates, a spectrum generated by this tool is likely to be more similar to a NCS, Munsell, or OSA-UCS spectrum than to the spectrum of a Pantone chip. - Illuminants for 3 components fit: A, C, D50, D55, D60, D65, D75, D93, E, F2, F7, F11, plus two Custom Illuminants. - Illuminants for 6 components fit: A, C, D50, D65, E Please consult the PatchTool Help manual for more information on the particularities of this tool.