To appreciate the contribution of Dr. Neugebauer, it is useful to understand the art of color reproduction in printing as it was practiced in the United States from 1930 to 1940. Color printing by lithography, letterpress, and gravure in the 18th century was an art form. Color printing plates were created and printed by artists. Dramatic results required the use of several plates. In the early part of the century J.C. LeBlon made color prints using four plates, red, yellow, blue and black. He is often credited with the theory of three-color printing which states that all colors can be produced with this limited palette. His ideas and the method of producing images by hand engraving continued to be the practice even after photomechanical processes were well developed, and the practice survived well into the 20th century.

In color reproduction system, 'a role of the Neugebauer equations is a mean to get a set of dot areas for three color or four color reproduction starting from tristimulus value of a target color. To apply the Neugebauer equations, one has to consider each step of system carefully to achieve good color reproduction starting from input device to final printing techniques. The target color has to be described by colorimetric quantities instead of three color densities. Dot areas as unknown in. the simultaneous equations are effective dot areas printed on the papers effected by dot gains during workshop operation including Yule-Nielsen effect. It is necessary to have system analysis on total printing process and physical analysis on each step involved to apply the Neugebauer equations properly.

Within several years of establishment of the CIE's Standard Observer, Neugebauer based upon it a device-independent interpretation of ink mixture in halftone color reproduction. Despite limitations of the model, his approach is of fundamental importance at a time in which document preparation in distributed computing environments is coming of age. Fruition of this technology demands a device independent or colorimetric method for representing and rendering color. A commercial, digital system for implementing such an approach (Kodak Designmaster® 8000) has been described and will be reviewed here with particular regard to the output of color imagery on four-color printers. Inversion of Neugebauer's model for conversion of color to device specific signals must be constrained by the color gamut of the output medium and the utilization of the black printer (Gray Component Replacement). The interaction of the black printer with the device gamut and its effect on image quality and metamerism will receive detailed consideration. It will be shown that colorimetry is a powerful tool in maintaining accurate color reproduction during substitution of black for chromatic components, but that properties of the colorants must also be considered in order to realize commercially acceptable GCR. Section 7 of the paper is an enumeration of summary conclusions.

The gamut of color in digital color printer is discussed with a simple color mixing model based on Neugebauer theory. A colored halftone area is composed of at most 8 colored dots: Cyan, Magenta, Yellow, Red, Green, Blue, White, and Black. It is shown that a color gamut and a color-locus change by the 2 colored dot overlay method. Typical color changes in thermal transfer printer were observed experimentally in coincidence with theotretical estimations. The dot allocation of dither matrix causes the significant changes in the hue of red tone and the gamut of bluish colors.

The problem of dot gain, either optical or mechanical, has always been attracting a keen interest of printers mostly from the view-point of tone reproduction. The quality of the light associated with dot gain tends to differ from that not associated therewith, thus the present paper will deal with the effect of dot gain on color reproduction of lithographic print. To predict color cordinates of a monochromatic print from its dot coverage a modification of the Neugebauer equation is proposed which introduces a second color component for each printing ink in order to better describe the colorimetric behaviors of inks. An approach of print quality control based on the colorimetry using the present modification will also be presented.

The Neugebauer equations give us a set of dot areas to reproduce a given target color( X, Y, Z ) as solutions of non-linear simultaneous equations, not only in case of three color reproduction but also four color one. We have only three equations, therefore one dot area has to be fixed prior to solve the Neugebauer equations. The way to apply black printers could be classified into varieties, according to how to fix one dot area among four ink dot areas. Conventional black printer given by black rate with minimum dot area in three color reproduction, maximum black in which one of three colors is zero and skeleton black to avoid black dots for high-light are discussed in this paper. Studies give us clear view on the black printer applications in different manners and results are summarized as restatements of concepts and redefinitions of technical terms. Almost technical terms used in past related with black printers explain well local photographic processes which were used before digital handling as continuous tone color separation. Now in modern processing of color information, it is not necessary to hold simulation of photographic image treatments. Relation between target tristimulus values and four dot areas is directly given by the Neugebauer equations.

As Lambert-Beer's Law in density modulation images, Neugebauer Equations are the basic equation for color reproduction of dot modulation images. Its significance increases with the advance of digital color printing technology. Its' applications have been diversely enlarging to identify the relationship between dot allocation and color gamut', to forecast reproduced color2, and to discuss the achromatic synthesis in principle^{3, 4}. As well known, its principle is that "color is reproduced by averaging additive color mixture of basic 8 colors' area and stimulus determined statistically by the Demichel's law" . The significant assumption here is "the independency of each color area", that is, the coverage and color stimulus of each color area are not influenced by those of neighbor. However, in an actual dot modulation image, optical diffusion and mixture occur within image as known as Yule-Nielsen's effect (Y-N effect). Therefore, the former assumption cannot be adapted on actual images. Since various marking technologies have their own optical diffusion and mixture respectively due to their marking principle and image structure, it seems that an overall comprehension for color reproduction of these images is required from these technologies. And besides, reconstruction of color reproduction theory including density modulation images will be more necessary in future. For this purpose, new theoretical approach adding Y-N effect to Neugebauer equations might be indispensable . From the viewpoint, this paper introduces the full-color image structure models which quantifies optical diffusion and mixture within recorded image and mentions the physical interpretation of Y-N effect in full-color image. Next, by using Neugebauer equations with Y-N effect6, we analyze the achromatic synthesis and propose the theoretical method for black determination applicable to all image formation, through density modulation to completely binary image.

Four different scanning Color Electronic Pagination System (CEPS) devices were tested to study their conventional and Grey Component Replacement/Undercolor Addition (GCR/UCA) tone and color response in the 4 color Positive Acting Offset Lithographic printing process. A common transparency input and ganged printing output was used. Inter and intra machine differences are disclosed. A new depiction of the full tone reproduction characteristics is presented for several different levels of GCR/UCA and conventional printing.

The possibilities to achieve a good four-colour print quality are much more limited in newspaper printing than in heat-set or gravure web printing. Nevertheless, the percentage of four-colour printing and, consequently, the quality requirements continue to grow in newspapers. One way of making the printer's work easier in the colour separation process is the socalled Grey Component Replacement (GCR). This technology has been available with digital scanners for several years. Our laboratory has also studied its applicability, especially in newspaper printing, on different occasions.

Using video sources in printing opens a range of opportunities - news gathering with camcorders, publishing of broadcast TV-pictures and other video material and using video cameras as input to pagination systems. However, there are several technical problems inherent in the transition from moving video to print. These are the color subcarrier influence, the camera and recorder noise, a certain smear in the printed picture and the matching of print colors to video colors. The aim of this work is to show through experiments, that proper digital processing can substantially reduce these problems and improve the usability of video sources in printing.

Recently, digital hard copy machines have drawn a great attention because they have good performance of signal processing. Hard copies are directly obtained from video signal by connecting CRT monitor and digital hard copy machine. At that time, many signal processing are considered to produce the desired images. In the color reproduction process, the processing technique that can reproduce saturated and luminous color of CRT monitor by using color ink must be considered, because the color gamut of CRT color monitor is wider than the one that uses in ink for printing purpose. This paper proposes a method of color rearrangment along the constant hue locus to produce correctly the hue of the colors that exist between the ink gamut and CRT gamut. And then, it is shown that the effect is observed clearly in red comparing to the usual color rearrangment.

Black and white film is widely accepted as being more permanent than color film. Color separations on black and white film are routinely prepared from commercial color motion picture negatives to ensure that valuable film endures. At some point in the future, the separations are reconstructed onto color film and fresh release prints are struck for distribution to theaters. Color separations are rarely made from still color images to enhance their longevity, due in part to the complexity and expense of separating and reconstructing color images. The author has developed hardware and a set of procedures to make and reconstruct color separations at very low cost, and, if warranted, in high volume. Sets of separations are exposed in register sequentially onto sprocketed, continuous tone 35mm panchromatic microfilm. Sets of separations are reconstructed onto common color sheet film or electronic sensors with a registered tri-color viewer/printer that is suitable for use in room light.

During the 1930s and 1940s a number of light reflection models were proposed and validated with experimental data. Of particular note are the 2 flux model of Kubelka and Munk (1931) and the color reproduction model of Neugebauer (1937). The manual measurement and data processing capabilities available at the time these models were proposed were adequate to prove model validity. However, the time required to make the measurements and calculations for all but the simplest applications made the wide spread use of these models impractical. Most of the potential applications for these models had to wait some 30 to 50 years to be realized.

Color-separated samples of several originals by expert scanner operators were collected and studies were niade into the relevance with the cumulative density histogram (CDH) of the original in order to automate the work of setting up the scanning conditions at a color scanner for prepress which is used for reproducing high-quality color originals. From the scanning results, it was discovered that the highlight and shadow densities to be setup were closely related to the densities in the proximity of the minimum density (Dmin) and maximum density (Dmax) of the CDH, respectively, and that the characteristics of tone reproduction are dependant on the density range of the original. An automatic setup model based on this knowledge was established and experiments have been carried out using a newly developed color flatbed scanner. The experimental results based on the proposed model were satisfactory. The color flatbed scanner houses newly developed CCD sensors and optical system, and high-speed, high-quality processing has been enabled by digital circuits. An easier-to-operate scanner has been achieved through an automatic setup function and easy handling of originals.

Unsharp Masking, abbreviated as USM, is one of the few terms that is transferred from photographic color separation technique to modern electronic separation in a scanner. In photographic separation, the color correction mask is made unsharp to enhance details in the reproduction. In a color separation scanner, the principles remained the same, however, a different technique is used to create an optical illusion to enhance sharpness or details in the reproduction. During scanning, when there is a change of density in the copy, two fine lines are generated at the borders of the transition, a lighter line and a darker line at the borders of light and dark edges respectively of the density change. This is possible by scanning the copy with the main aperture as well as a separate larger aperture called unsharp masking aperture. When the separation is in progress, the signal from the unsharp masking aperture is compared with the signal from the main scanning aperture at a differential stage in the computer. If there is a density change in the copy, the larger unsharp masking aperture senses the change sooner than the smaller main aperture, and at this point, an additional signal is generated and added to the main signal. This makes it possible to create the black and white lines at the borders of a density change. In addition to this function, the same black and white lines can also be produced at the borders of transition of a color by transmitting the unsharp masking beam through any one of red, green, or blue filters. A combination of these apertures and filters can be selected by adjusting a pair of wheels located on the scanning head as in Hell scanners, or by changing specific inserts as in Dainippon Screen scanners. When used moderately, the black and white lines at the borders of a density or color change will create the effects of sharper details in the reproduction. In addition to the above mechanical controls, electronic controls are also provided in most scanners to increase or decrease details and, if necessary, to suppress any unwanted enhancement in certain areas of the reproduction. The presentation explores the various types of detail enhancement and suppression controls used in a scanner and their effects on the reproduction.

Several terms are used to determine the optical properties of paper and board. Brightness, whiteness, diffuse reflectance factor, diffuse blue reflectance factor, specular gloss, spectral reflectivity and whiteness and yellowness are the used terms. The mainly used term is brightness of paper, an important property in many specifications, but this property has no visual perceptual foundation. Instead it is based on the filter chosen to measure the reflectance of pulp in the region most sensitive to the effects, of bleaching. Therefore an increasing demand for a specification of whiteness can be observed. Belonging to the concept of color, whiteness has to be measured and interpreted in the scope of CIE (Commission Internationale l'Eclairage) based on colorimetri tristimulus data transformed to agree with the perceptual assessment of whiteness. Human observers differentiate between the whiteness of the object being viewed and its brightness. A special index of whiteness is needed. No general agreement was so far reached regarding the best index which could and should be adopted universally among the two recommended by the CIE. Nearly every white sample is a little colored, having bluish, greenish or redish tint. In the post no numerical measure of tint was assigned to any of the whiteness indexes. Further problems arise that fluorescent whiteness agents are added to paper and board to increase their whiteness. This requires not only instrumental design and calibration but also the illuminant to be adopted for such measurements.

A new apparatus for measurement and discrimination of color prints with gross has been developed, composed of a zoom lens, a mirror box, MOS cameras, a microcomputer and a color image processor. In this system, it is possible to take freely blurred image with the zoom lens controlled by the microcomputer, and a new color measurement method based on the obtained blurred image is introduced. From the experiments it became clear that the gloss can be lost with the blurring of the image, and the gloss can be values of the image are not affected if the blurred images are restorated by the modified Wiener filter. As the results, we conclude that the developed system is significant for the color measurement and distinction of prints with gross.

According to " New Printing Dictionary " ( issued by Japan Printing Society),' " Printing" is a technique to make a plate according to the original, to charge inks on the plate, to impress and transfer to paper or other substances, and to get multi-copies. Especially, from the color reproduction point of view, it is necessary to select adequate inks for the kind of original and for the type of plate which is made according to the original. There are five methods classified for color reproduction in printing. In this report, I describe mainly that 00 Process color inks which reproduce color. 0 Color matching, especially C.C.M. ( Computer Color Matching ) which is applied color reproduction with special mixed colors. Regarding to the process color inks ( blue and magenta ), I mention the history of establishment and the present state, and the difference of pigments which is used. Concerning CCM, I describe the principle, the points of problem, the introducing effect, the accuracy as the system.

Offset printing is the most popular process in the present printing industry. It amounts to over 60% of the total commercial printing production in the world. One of the needs for the printing presses in the printing field is the production of high and stable quality printing with few operators and less skills. The key factor is how inking should be controlled in the offset printing. For that purpose many devises and systems have been developed and applied to printing presses, for instances, control of ink temperature, ink supply control with close loop circuit, simple inking device such as keyless inking system, and so on. Almost all of them seem to be neither successful in practical use, nor accepted in the market. The reason is clear that they all disregard the important function of dampening solution in the offset printing process. According to Mitsubishi's researches, dampening solution has two functions; 1) Protection of the non-image area from inking 2) Optimization of tone reproduction The second item is corresponding to the "balance" of ink and dampening solution, but the true meaning of the balance has never been analysed. Mitsubishi's basic researches of the inking behavior on printing presses have made it clear that the good balance is equivalent to a optimum emulsion state of ink and dampening solution on inking rollers. The optimum state is explained with printing results.