A high-quality monochrome photographic image is formed using a high-resolution color ink-jet recording apparatus. When a monochrome mode is selected, density signals are produced such that they include at least one density signal corresponding to a chromatic color material and a density signal corresponding to an achromatic color material and having a value greater than the value of the at least one density signal corresponding to the chromatic color material. A slight recorded color deviation that can occur when the achromatic color material is recorded on a recording medium is compensated for by adding a small amount of chromatic color material having a hue which cancels out the recorded color deviation. Thus, a high-quality gray scale image is obtained without having recorded color deviation or color transition.