Color hardcopy derived from digital photography is produced using digital data supplied to a printer. The number of digital information levels is decided by image processing conditions and is manipulated using a personal computer. The typical number of levels for continuous-tone rendition of primary color images red (R), green (G) and blue (B) is 256 levels, equivalent to 8 bits (2⁸ steps). To date, there have been few studies on the relationship of the number of levels of input image data and output image quality of prints.¹ This report discusses the relationship as it applies to thermal dye-transfer prints. Further, it discusses the appropriateness of thermal dyetransfer printing for continuous-tone pictorial image formation. The evaluations are based on both subjective human viewing and objective colorimetric measurements to discriminate between different patches printed in increments for 256-level data. The results show that a maximum 94% of the input 256-level image data, capable of being seen express different densities in the magenta and black samples under visual examination and about 10 million colors were estimated recognizable on the full-color print in a physical examination. Furthermore, the appropriateness of thermal dye-transfer printing is discussed. A digital data level of 8 bit for a hardcopy system was almost sufficient and reasonable to match human vision and to express continuous tone on the reproductions.