Color matching system

Experienced color matchers can achieve a good color match by trial and error without using any instmmentation. In some cases, however, this technique can be a lengthy process, and should the desired match be outside the color space defined by the available color standards, the technician might spend too much time just to determine that the match is not possible. To get the most cost-effective match using a low metamerism in the shortest possible time, the use of a computet color matching system is preferable. 

Foundry resins, phenolic, 18 788—789 Foundry sand, chromite application, 6 493-494, 497 4A zeolite. See Zeolite 4A Four-component color matching system,... 

Using many-flux technology, computer color-matching systems can automatically formulate with or without white, at all levels of opacity, from a single database. In addition, satellite systems can offer added value by providing the same high-quality formulation results as a full system, with a low cost and feature limited satellite system. 

The database is an integral part of a computer color-matching system. It is the characterization of all pigments and resins from which formulas will be calculated. Creating a database involves producing samples of pigments, resins, and known mixtures of each. Once database samples are measured and saved to the database, the database is calibrated. 

Contemporary color-matching systems enable sample additions to the calibration database for increased performance. In addition, the sample set is variable for each individual colorant. An application may require only 5 samples for a yellow colorant but 12 samples for a reflex blue to achieve optimum performance. Note that additional samples, are used in the calculation of the absolute K and S data. These samples are not a function in a search-and-correct calculations. 

Sample Characteristics. In many Kubelka-Munk color-matching systems the user is required to present an opaque sample to the spectrophotometer. Depending on the application, this can be done a number of ways. For coatings, the technique of cross-coating several layers of colorant until opacity is achieved is commonly used. The generated sample then has become inconsistent with the typical process thickness. Although this can add error to the formulation, it will still adhere to the limitations of the Kubelka-Munk equation [7],... 

Both reflectance and transmittance measurements can be applied to the same database. For plastics and translucent liquids and for printing or coating on nonopaque substrates, this is a very important feature. In these applications it is not sufficient to match a standard in reflectance only a transmission match is equally important. Contemporary color-matching systems can combine both types of matches in one calculation using only one database. To use this capability, it is necessary that the spectrophotometer measure both the reflectance and total transmittance of the sample. 

Considering the full scope of many applications, traditional color matching has not provided a total solution for color matching. With the addition of the many-flux theory, and spectral matching, contemporary color-matching systems are the next step in providing a total solution for color formulation. 

The RAL is a color matching system used in Europe and is used for varnishes and coatings. The RAL associates numbers to individual colors (11). 

Color-order systems, such as the many MunseU collections available from Macbeth, have been described previously. Essential for visual color matching is a color-matching booth. A typical one, such as the Macbeth Spectrahte, may have available a filtered 7500 K incandescent source equivalent to north-sky daylight, 2300 K incandescent illumination as horizon sunlight, a cool-white fluorescent lamp at 4150 K, and an ultraviolet lamp. By using the various illuminants, singly or in combination, the effects of metamerism and fluorescence can readily be demonstrated and measured. Every user should be checked for color vision deficiencies. 

It is desirable for the record to have an objective statement of the nature and degree of color deterioration. The simplest, but least desirable, method is comparison of sample color with color charts or plates such as those used in the Munsell system, Ridgeway s color standards, or the Maerz and Paul dictionary of color. Such a method is limited in value because of the difficulty of obtaining true color matches, and because of variations due to human error. The use of color charts or plates may be much improved in the Munsell system by employing a disk colorimeter (29). Kramer and Smith (21) have pointed out that the results obtained in its application to foods are sometimes difficult to explain and compare, and that the method requires special training of the operator and is tedious and cumbersome. 

A system for emittance color matching is given in the following ... 

Nevertheless, it is well to note that it was the subjective observation of the lack of correction for luminosity in the Munsell System that gave impetus to the development of the CIE Color System. The major problem vidth the Munsell system was that each person attempting to match colors did not produce the exact same result. So color matching became dependent upon the person. 

When Munsell devised his color space, he did so on the basis of minimum observable color perception steps. But the problem with the Munsell System was one of reproducibility, which the CIE Standard Observer cured. In formulating a color match, one wants to be able to predict the correct concentration of colorants required, whose scattering and absorption properties are known, i.e.- the lightness, so as to match the sample submitted, starting with their spectrophotometric curves. In practice, this is not so simple, since two colors must have identical spectrophotometric curves to be exactly equal. It turns out that the human eye will identify the two colors to be equal if their spectrophotometric reflectances are reasonably close. Two colors may appear to be equal under Daylight illumination, but quite different under incandescent lamp illumination. These colors are known zus "metamers" and the phenomenon "metamerism". 

In an extension of their work, Goodhart and coworkers developed a system [45] whereby the final desired color of a compressed table formulation was first chosen from a standard color chart (such as the Munsell compilation [40]). This color was then analyzed as to its CIE parameters, and these parameters were in turn used to develop a colorant combination that would produce a match of the desired color. The ultimate end of this work was to produce a database of sufficient depth that the empirical nature of color matching could be eliminated. 

Computer-aided programs, for SLS equipment selection, 11 348 Computer analysis, of DNA sequence information, 12 510-512 piping system sizing using, 19 473-474 Computer-assisted color matching,... 

This theory is especially useful for computer color matching of pigmented systems [1.22]-[1.24] absorption and scattering coefficients are combined additively using the specific coefficients of the components multiplied by their concentrations. 

A more refined method uses the Duboscq colorimeter. This instrument features a dual-matched optical system. Uniformly intense light is incident upon both colorimeter tubes and the difference in absorption of the standard and unknown solutions is compensated for by adjusting the thickness of solution through which light passes. When the two colors match Cs =C,bJbx. 

In retrospect, this was another one of Upson s devious activities. The four-color Dylux, which the marketing people liked, offered a quick, and inexpensive four-color overlay system, which could have competed effectively with 3M s color overlay systems. The sensitometry, which we had developed, showed remarkable consistency only the black required a bit longer exposure to bring the color to full density. This was established by Dr. E. E. Grubb, of Photo Products, who had been asked to establish the performance of these films. The cyan was an excellent color match, and the red and yellows could be tuned close to the lithographic standards. Another company, with a more open-minded research management would no doubt have made a product out of all that. 

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