Generating spectra from tristimulus values

Method for automatically generating reflectance spectrum values from tristimulus values using a computer system administrating a database with data matrices of reflectance spectra of different colors differentiated by one or more process parameters, wherein the one or more process parameters include print technology, substrate, and print order of inks, the method comprising:

• a) classifying given tristimulus values of a color with regard to the one or more process parameters,
• b) identifying in the database a data matrix of reflectance spectra of said color with matches of the one or more process parameters matching most, and
• c) using the data matrix of reflectance spectra of said color identified in step b) to define the reflectance spectrum values for said color and selecting the one or more process parameters for a print process as needed, based on the reflectance spectrum values for said color;
• wherein the data matrix of reflectance spectra of said color identified in step b) is reduced to basis vector data within a PCA (principal component analysis) process to yield correct tristimulus values of the reflectance spectra, based on an equation
• r=μ+(x−μCT)*(BCT)−1B
• wherein r be the spectral reflectance, μ be a mean vector of the data matrix of reflectance spectra of said color identified in step b), x be a vector of tristimulus values, C be a color matching function weighted by a given illuminant, and B be a matrix of the PCA (principal component analysis) basis vectors.