1. A tone setting assisting method comprising the steps of: (a) obtaining a gray image; and (b) printing together a plurality of monochrome images obtained by imparting a plurality of different tints to the gray image, wherein the step (b) includes calculating an ejection amount of at least one chromatic ink for each of the plurality of tints, based on lightness level values of the gray image, wherein method further includes the step of calculating, with respect to each of the monochrome images, achromatic ink ejection amounts associated with the gray image based on a table that associates lightness level value with ejection amount of at least one achromatic ink having predetermined lightness, the table further associating the lightness level values with ejection amounts of the chromatic inks, the ejection amounts of the chromatic inks being calculated for each of the plurality of tints, by means of multiplying, by predetermined coefficients, the ejection amounts of the chromatic inks associated with the lightness level values in the table, the predetermined coefficients being obtained by dividing maximum values of ejection amounts of the chromatic inks corresponding to the plurality of tints, by maximum values of ejection amounts of the chromatic inks associated with the lightness level values in the table, the maximum values of ejection amounts of the chromatic inks corresponding to the plurality of tints being set to a plurality of values at a predetermined interval within a predetermined range, and wherein the step (b) is executed repeatedly, with the predetermined range and the predetermined interval in iteration N (where N is an integer equal to 2 or greater) of the step (b) being respectively smaller than the predetermined range and the predetermined interval in iteration N−1 of the step (b).