A method for controlling the operation of a printer apparatus, the method comprising the steps of: determining which one or more colorant units have been loaded into the printer apparatus, each colorant unit being configured to store at least one colorant; retrieving colorant information from each loaded colorant unit, the colorant information comprising one or more characteristics of one or more colorants contained in the colorant unit, wherein a characteristic of a colorant comprises one or more of reflectance information relating to the colorant, reflectivity information relating to the colorant, opacity information relating to the colorant, transmissivity information about the colorant, information relating to a drop or particle weight of the colorant, information relating to a drop or particle shape of the colorant, or information relating to a drop or particle size of the colorant; determining a colorant-set configuration using the colorant information retrieved from each loaded colorant unit, wherein the colorant-set configuration comprises the set of colorants of the loaded colorant units, and wherein the step of determining a colorant-set configuration comprises the steps of comparing the colorant information from the one or more colorant units loaded in the printer apparatus with a predetermined set of valid colorant-set configurations; configuring the operation of the printer apparatus according to the determined colorant-set configuration, wherein, if the colorant-set configuration does not match one of the predetermined sets, the method comprises: computing parameters for configuring the operation of the printer apparatus based on the retrieved colorant information. determining which one or more colorant units have been loaded into the printer apparatus, each colorant unit being configured to store at least one colorant; retrieving colorant information from each loaded colorant unit, the colorant information comprising one or more characteristics of one or more colorants contained in the colorant unit, wherein a characteristic of a colorant comprises one or more of reflectance information relating to the colorant, reflectivity information relating to the colorant, opacity information relating to the colorant, transmissivity information about the colorant, information relating to a drop or particle weight of the colorant, information relating to a drop or particle shape of the colorant, or information relating to a drop or particle size of the colorant; determining a colorant-set configuration using the colorant information retrieved from each loaded colorant unit, wherein the colorant-set configuration comprises the set of colorants of the loaded colorant units, and wherein the step of determining a colorant-set configuration comprises the steps of comparing the colorant information from the one or more colorant units loaded in the printer apparatus with a predetermined set of valid colorant-set configurations; configuring the operation of the printer apparatus according to the determined colorant-set configuration, wherein, if the colorant-set configuration does not match one of the predetermined sets, the method comprises: computing parameters for configuring the operation of the printer apparatus based on the retrieved colorant information. <EOS>