1. A method of halftoning an image by an image processor for extended-colorant printing comprising: performing a quality ranking of a plurality of periodic halftone screens within a given screen set to be used for halftoning an image spot color, giving the screen which generates the least amount of undesirable effects the highest quality ranking and the screen which generates the largest amount of undesirable effects the lowest quality ranking; ranking the objectionability of the colorants used to produce the image spot color for one or more objectionability factors relating to image quality defects; creating halftone screen-to-colorant assignments using ranked ordered pairing of the ranked screens and ranked colorants, pairing the screen having the highest quality ranking with the colorant having the highest objectionability, pairing the screen having the next highest quality ranking with the colorant having the next highest objectionability, and continuing the pairing in order until the screen having the lowest quality ranking is paired with the colorant having the lowest objectionability; and halftoning the image applying the halftone screens to their respective paired colorants.