the principal task in graphic arts reproduction is to convert input images , such as continuous tone original images , into output images , such as half - tone images , to permit , for instance , the creation of half - tone prints on a printing press . in this process , tones from the original image are typically altered or affected in two important ways . first , the printing conditions substantially affect production of an optimized half - tone representation of the original continuous tone image . second , the operator often needs to modify certain tones from that in the original to bring out more or less detail to achieve a desired artistic effect . this invention allows the operator to determine and adjust for printing conditions and original tone quality in a particular system and under a particular set of operating conditions , thus greatly reducing the time - consuming experimentation that operators have previously had to endure to obtain acceptable results .