We made theoretical approaches concerning the optical property of a pigment-containing system to understand the conditions under which an enhanced contrast can be achieved. Maintaining a uniform distribution of pigment particles in thin film well, as in millbase dispersion,is considered critical for a higher contrast. As a specific case, we estimated the effect of a polymeric binder on the contrast ratio. Chemical composition of the dispersion binder has a huge effect, and carboxylate in its long side chain plays a favorable role. Using this binder, we were able to obtain a smooth surface and uniformity, and an enhancement of contrast ratio in the colorant film.