According to recent increase of RGB data input from digital camera to press printing workflow, color and image reproduction incidents are becoming very remarkable. In order to identify these issues and solving methods, we held a joint workshop of four image science related societies "Color reproduction issues from digital camera to hardcopy—its ideal and real—". This special issue is constructed by papers based on presentations in this workshop. This paper describes its intent and background.

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Gradation characteristics and color spaces of digital cameras are described, and the effects caused by them on the image quality of the total system from the shooting to the appreciation (viewing) , especially color reproduction, are considered.

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In printing companies, receiving images taken with digital cameras is rapidly increasing. Though such a digital camera workflow is expected to shorten lead time and to improve quality of printed matter comparing with the workflow of silver salt film camera, the workflow often brings down reverse results. To solve this problem, we published "A Guidebook to Create Images for Commercial Printing by Digital Cameras". In this guidebook, we wrote some rules and knowledge to create images for commercial printing by digital cameras. In this paper, we will explain how to create images for commercial printing written in the guidebook, while introducing some cases in the printing company.

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The purpose of color transform processing by printers is transforming digital color value of images to amount of colorant of the printer. Digital color value is transformed to colorimetric value by simple equation based on monitor device model. The shape of monitor device gamut is different from the one of printer gamut. So the Gamut mapping is necessary to match monitor color to printer color. Gamut mapping has variation depending on the concern point. The transform from colorimetric value to amount of colorant is not unique. To determine the transform it is concerned to reduce graininess and to extend gamut size. In the sRGB scheme it is general to store the series transform information in one look up table. On the other hand in the ICC scheme the series transform information is stored in three different elements which correspond to the step from digital color value of images to colorimetric value, the step from colorimetric value to printer device digital color value and the step from printer device digital color value to amount of colorant of the printer.

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There are two important arrangements in digital color workflow from scene to output such as monitor and print, which are image format and color space including image state description. This report explained several issues such as important concepts (image state, ICC profile), problems and possible solutions for pre-press color workflow.

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Only the green primary of AdobeRGB is higher chroma than that of sRGB, but both red and blue primaries of AdobeRGB and sRGB are the same. Color gamut of AdobeRGB is wider than that of sRGB in not only green region but also red and blue regions. It originates from higher luminance of red and blue primaries of AdobeRGB than those of sRGB.

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A system for photocatalytic water splitting by a thin AgCl layer, which has been proposed by Calzaferri and others, is surprising to those, who are involved in the research on photographic systems with silver halide (AgX) microcrystals as photosensitive elements. From the viewpoint of the solid state physics and photographic sensitivity of AgX microcrystals, analyses are made in this paper on the properties and behaviors of AgX layers in the proposed system, including the formation and dissociation of excitons to create photoelectrons and positive holes, transport of photoelectrons from the interior to surface of a AgX layer, formation of silver clusters owing to the reaction between photoelectrons and silver ions in an electrolyte solution and a AgX layer, transport of positive holes from the interior to surface of a AgX layer, photo-decomposition of a AgX layer by positive holes to form halogen molecules, oxidation of water by positive holes to form oxygen gas, and recombination between photoelectrons and positive holes. The results of the analyses have given explanations for the fact that AgCl is suitable for the proposed system and the best among AgXs.

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After the 1970's on, several manufacturers including Fuji Film, Konica and Agfa-Gevaert participated in innovating color photographic materials by adding their own coupler chemistry to the technological architecture built by Kodak before then. One area of their major advances was development of the couplers having a coupling-off organic group. One of their functional forms was two-equivalent coupler which made the dye-forming process efficient and made the photosensitive layers slim. And another was DIR coupler which improved dramatically the image quality of color negative materials. In this paper a historical overview of these innovations is constructed from the technical documents, mainly patents.

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A major difference between silver halide photography and digital photography lies in the way of processing image data. Parallel processing of the whole image area can be accomplished in silver halide photography. However, image data must be processed serially in digital photography, and this serial processing of image data is called "scan". In silver halide photography, an almighty device "film" does everything from signal conversion, signal processing to signal storage. But separate devices take each role in digital photography.

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In the research and investigation on the historical materials and cultural properties, not only conventional RGB digital images but also spectral reflectance images serve valuable information. However, some suitable techniques to extract effective information corresponding to the purpose of the use of the spectral reflectance images are desired because the spectral reflectance images have so huge of information.
In this article, a method for investigating the historical materials and cultural properties will be described. This method can extract useful features relating to color compositions in the cultural properties. In this method, the measured spectral reflectance images of the icons, which are examples of the cultural properties, are clustered and the principal component analysis is applied in each cluster. The first principal component in each cluster is used for approximating the original spectral reflectance. The color difference caused of this approximation is calculated and used to control features to be extracted from the icons. Based on this number of clusters, results of the clustering are compared and possibilities of this method for further investigation are discussed.

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