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.
Shin Ohno, Toyoko Fujii, Koichi Oka, Naoya Kato, "Image Quality of Digital Photography Prints: I. Color Quality of Thermal Dye-Transfer Prints" in Journal of Imaging Science and Technology, 1998, pp 269 - 275, https://doi.org/10.2352/J.ImagingSci.Technol.1998.42.3.art00012