The present invention relates to the acquisition of color images by a sensor including a plurality of photosites comprising spectral sensitivities that can to be different between photosites. The invention provides for a digital processing of signals emitted by the photosites, which comprises applying a spatial-chromatic transfer function to said signals, taking into account a variety of spectral sensitivities of the photosites. The sensor can then be devoid of a physical matrix of color filters. Spectral calibration of the sensor is also provided for this purpose, thus comprising the following steps: obtaining spectral sensitivity data of each photosite (S91), building a spatial-chromatic transfer function (S94) taking into account a variety of said spectral sensitivities of the photosites, and applying same to the signals emitted by the photosites in order to compensate for the aforementioned variety of sensitivities.