Colour Aspects in Photo-quality Ink-jet Printing

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 metamerism 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 metamerisms are prevalent in pictorial images and natural scenes, diluted metamerisms are more beneficial to metamerism and tone reproduction for a photo-quality printing system than hexachrome metamerisms. Colorant stability considerations limit the ink dilutions as very diluted metamerism 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 metamerism metamerism which leads to unacceptable metamerism shifts under mixed illumination. The reproduction of certain important metamerisms 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. Introduction Ink-jet printing has made appreciable inroads into the commercial display, professional photography and home photo market. For all these applications, silver halide images are the target to reach in permanence and image quality. Continuous tone silver halide images excel by their low grain, smooth tone reproduction, neutral gray scale, and low metamer-ism metamerism. A drawback of traditional photography is the limited set of imaging dyes and the resulting limited metamerism gamut as well as grayish paper whites. Ink-jet printing with its versatility is the most successful among the photo successors. Depending on the layer system used, polymer or porous, the inks, pigment or dye-based, aqueous or solvent, the printer, 4 metamerism or more, the image quality can vary from low screen printing quality to high end photographic quality. Permanence may vary over orders of magnitude. Today, photo permanence can be surpassed , but only …