The output color hardcopy in digital photography is printed by digital data supplied to the printer. The number of digital levels of information is decided by conditions of image processing and manipulation using a personal computer. For each color, the typical number of levels for continuous tone renditions of primary color images of red (R), green (G) and blue (B) is 256 levels, equivalent to 8 bits (28 steps). There were few studies on the relation of the number of levels of input image data and output image quality of prints1).This paper discusses the relation of number of levels of image data and the color reproduction on thermal dye transfer prints. Further, it discusses the appropriateness of the thermal dye transfer printing for continuous tone pictorial image formation. The evaluations used both subjective human viewing and objective colorimetric measurements to discriminate between different patches printed by step wise 256 level data.The results show that the maximum 94% of input 256 level image data responds to express different densities in magenta and black samples in visual examination and about 10 million colors were estimated to be physically recognizable on the full color print.Furthermore the appropriateness of thermal dye transfer printing was discussed. The digital data level of 8 bits for the hardcopying system was almost sufficient and reasonable to match human vision and to express the continuous tone on the reproductions.
Shin Ohno, "Color in Digital Photography Color Quality of Digital Photography Prints" in Proc. IS&T 5th Color and Imaging Conf., 1997, pp 100 - 104, https://doi.org/10.2352/CIC.1997.5.1.art00020