The present invention facilitates the calibration of printers and the color separation of input images into a set of inks by disclosing methods and systems for populating device-calibration lookup tables. The disclosed methods and systems rely on a comprehensive spectral prediction model which is capable of predicting at a high accuracy the reflectance spectra of halftone ink patches. The comprehensive spectral prediction model is composed of a first part predicting the reflection spectra as a function of physical (mechanical) surface coverages and of a second part comprising functions mapping nominal surface coverages to effective surface coverages. These mapping functions are calibrated by halftone patch wedges printed alone and by half-tone patch wedges printed in superposition with one or several solid inks. The part of the comprehensive spectral prediction model predicting the reflection spectra relies on a weighted average between one component behaving according to the Clapper-Yule model and another component behaving as the spectral Neugebauer model, extended to include multiple internal reflections at the paper-air boundary. The disclosed methods and systems can perform the color separation as well as the calibration of printers printing with standard cyan, magenta, and yellow inks as well as with inks comprising standard and non-standard inks such as Pantone inks (custom inks). They are also used for performing precise undercolour removal in order to carry out the color separation of images into cyan, magenta, yellow and black inks. They can further be used to carry out the color separation of images into cyan, magenta, yellow, black, light cyan and light magenta inks. In addition, the disclosed methods and systems can be used for printer control, i.e. to control printer actuation parameters in different types of printers e.g. liquid ink professional printers (offset, gravure, letterpress), electrophotographic printers, ink-jet printers, thermal transfer printers and in dye-sublimation printers.