1. A method of characterizing a sensor, said method comprising: obtaining a set of locations in a first color space, each of the set of locations being based on a response by the sensor to a corresponding one of a plurality of targets, each of the plurality of targets having a different reflectance spectrum; obtaining a set of parameters based on a decomposition of a reflectance spectrum of a surface into a combination of reflectance spectra of the plurality of targets; based on the sets of locations and parameters, obtaining a predicted response of the sensor to the surface.