The topic of photo-equality in hardcopy technologies has been widely discussed from the beginning of digital printing until today. Photographic quality prints can be made on desk-top printers with little compromises in permanence and performance. The paper compares the status of ink-jet prints in professional and desktop systems with commercial photography.The gamut of typical ink-jet dye and pigment-based prints and the influence of using more than four colour channels was investigated. In a 6-channel system, the addition of green and orange leads to a similar increase in gamut as the addition of diluted cyan and magenta. However, multi-level printing allows more continuous tone type tone reproduction and better image quality. Diluted colorants provide the gamut gain in high lightness areas. As light colours are prevalent in pictorial images and natural scenes, diluted colours are more beneficial to colour and tone reproduction for a photo-quality printing system than hexachrome colours. Colorant stability considerations limit the ink dilutions as very diluted colour dots may suffer from permanence defects.Photographic images may be displayed in areas with natural daylight, tungsten light or fluorescent light. They are expected to exhibit a neutral tone scale under all conditions. Very brilliant colorants and certain pigments are shown to have appreciable colour metamerism which leads to unacceptable colour shifts under mixed illumination.The reproduction of certain important colours is another factor in colorant selection and printer design for photographic reproduction. The paper tint of many ink-jet systems is very bright compared to typical photographic prints and their limitations in minimum density.
Eduard Baumann, Rita Hofmann, "Colour Aspects in Photo-quality Ink-jet Printing" in Proc. IS&T CGIV 2002 First European Conf. on Colour in Graphics, Imaging, and Vision, 2002, pp 448 - 452, https://doi.org/10.2352/CGIV.2002.1.1.art00095