Munsell

Methods are described for determining the extent to which original natural color is preserved in processing and subsequent storage of foods. Color differences may be evaluated indirectly in terms of some physical characteristic of the sample or extracted fraction thereof that is largely responsible for the color characteristics. For evaluation more directly in terms of what the observer actually sees, color differences are measured by reflectance spectrophotometry and photoelectric colorimetry and expressed as differences in psychophysical indexes such as luminous reflectance and chromaticity. The reflectance spectro-photometric method provides time-constant records in research investigation on foods, while photoelectric colorimeters and reflectometers may prove useful in industrial color applications. Psychophysical notation may be converted by standard methods to the colorimetrically more descriptive terms of Munsell hue, value, and chroma. Here color charts are useful for a direct evaluation of results. 

Conversion tables and charts now available make it possible to express I.C.I. data in forms in which a specified color and the significance of measured color differences can be more easily visualized. For example, I.C.I. values calculated from objective instrumental readings can be converted into the Munsell notation which evaluates the three psychological color attributes—hue, lightness (Munsell value), saturation (Munsell chroma)—on scales of approximately equal visual steps. In addition, the Munsell color charts offer one of the most convenient sources of material standards for direct color comparisons. 

If results of color measurements are expressed in Munsell notation, a reader can use Munsell color charts as an aid in visualizing approximate ranges of color differences involved. Such a means has been suggested (15) for expressing color of light-colored juices. The necessary experimental data were obtained with a reflection meter similar to the reflectometer described. 

The Munsell book standards corresponding to the limiting colors may even serve as material standards for industrial color control. In a material standard system the sample is compared with a standard by eye without the use of any meter or optical instrument. The success and popularity of these systems are largely due to their simplicity of application. The ability of the human eye to compensate for various illuminants and surroundings makes it possible for this system to give results even under mediocre conditions. The most critical work with material standards requires carefully controlled observing conditions. 

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. 

Once this fact was rccdized, it was understood that an average of what each person saw would have to be made if a standard system weis to be formed and promulgated. This led to the concept of the "Standard Observer". Thus, the research required to define and measure color took a completely different path from the original methods such as the Munsell Color Tree. 

On a practical basis, if we wish to set up this system, we would assemble a set of "color-chips". Each color-chip would be specified by two factors, H = hue, and V/C, which is value (grayness) modified by chroma (saturation). The actual number of layers in the Munsell Color Tree was determined by "minimum perceptual difference". That is, the minimum change that produces a visual perceptible difference. This arrangement specifies all light colors as well cis the dark ones. To use such a system, one would choose the color-chip closest to the hue and saturation of the test color and thus obtain values for H and V/C. However, it was soon discovered that the system was not perfect. Reasons for this include the facts that the hues defined by Munsell are not those of the primaries of the human eye. Furthermore, Munsell was somewhat subjective in his definitions of hues. 

In 1920, Priest showed that if the MunseU-Chlps were viewed on a white-background, the "brightness", i.e.- lightness as viewed by the human eye, could be related to the Munsell S5rstem by ... 

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". 

It was soon determined that the 1931 CIE chromaticity diagram, and lumincmce function, Y, are not representative of equal visual spacing, that is, equal changes in Y do not represent equal changes in visual perception for all values of Y. Nor do equal increments of x and y represent the same visual effect for all locations on the chromaticity diagram. In other words, there is a minimum perceptual difference on both x and y (i.e.- Ax and Ay). But, the size of Ax and Ay is not the same at all parts of the chromaticity diagram. This is the same problem that Munsell encountered and is due to the fact that the human eye is... 

The true test is how well the Munsell hues plot out on the CIE diagram. As can be seen on the right hand side of the diagram, the Value 5 - Chroma 8 hues do construct a nearly perfect circle. Thus, the MacAdam transformation is a definite improvement over the 1931 CIE system. In 1960, the CIE adopted the MacAdam System, having defined the equations (with MacAdam s help) ... 

Three attributes characterize color hue, lighmess (or value), and saturation (or chroma) and they are graphically represented in color solids (e.g., Munsell solid. Hunter solid). The Munsell Color Notation is a rapid, portable, widespread, and economical system of color determination. However, as it depends on sensory evaluation by panels, many laboratories prefer when possible to replace human judgment by instrumental techniques that are easier to handle. The CIELAB established by the Commission International d Eclairage (CIE) has become widely used with the availability of reflectance spectrophotometric instrumentation. 

Thompson, T.E., Grauke, L.J., and Young, E., Pecan kernel color standards using the Munsell color notation system, J. Am. Soc. Hort. ScL, 121, 548, 1996. 

Other properties Munsell color yellow-orange powdered solid density 1.41 g mL log Kan 4.1, thermally stable... 

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. 

Field pH, Munsell soil colour (dry moist), EC 1 5 (soil water), pH 1 5, XRD, laser particle size analysis, XRF (multiple elements), ICP-MS (after HNO3/HCKV HF/HCI digestion for multiple elements), ICP-MS (after HF/HCI/HNO3 digestion for Se), ISE (for F), GF-AAS (for Au), and ICP-MS after MMI extraction were performed. Full details of the sampling and analytical methods are given in Caritat Lech (2007). 

The typical Munsell color chart for soils covers only those colors described as being yellow or red or some combination of the two. This is not to say that... 

Figure 2.13. The 2.5YR (yellow-red) page of a Munsell color book. The value is from white at the top to black at the bottom. Chroma becomes higher from left to right.

Munsell Soil Color Charts. Baltimore, MD Kollmorgen Corporation 1975. 

Chronology of the Origin and Progress of Paper and Paper Making , J. Munsell, Garland (USA), 1980, ISBN 0-8240-3878-9. 

Colour (Munsell) Oxide R ractive index Other... 

There is a variety of systems used to quantify colour and to assist in the comparison of colours, two important ones being the CIE-Lab system and the Munsell colour classification. Details of these systems are given in Wyszecki Styles (1982) and Heine Volz (1993). Very briefly, the GIF systems are based on the principle of tri-... 

In soil and other geosciences, colour is commonly measured using the Munsell colour classification system. This system defines colour in terms of hue H (position of colour in the spectrum), chroma C (the purity of the hue going from the grey to the pure colour) and value V (the lightness of the colour on a scale ranging from black to white). The reflectance measurements can be converted into the characteristic parameters or coordinates of the different measurement systems. 

Tab. 6.5 Munsell hue, value and chroma and CIE L C H° colours of synthetic Fe oxides (mean, minimum-maximum). N = numberof samples (Scheinost, Schwertmann, 1999 with permission)...

Fig. 6.11 Munsell colours of synthetic hematite, ferrihydrite, lepidocrocite, and goethite samples (Courtesy A.C.Scheinost Scheffer Schachtschabel,...

Fig. 6.13 Munsell hue of goethite as a function of substitution with transition metals ( Courtesy A.C.Scheinost Schwertmann Cornell, 2000, with permission)...

Schwertmann Pfab, 1994) (see Plate 6.II). Mn substituted hematites are blackish. In case of A1 substitution, the observed shift towards redder hues is due mainly to the associated decrease in particle size (Scheinost et al. 1999). Structural A1 does not significantly influence the hue and chroma of synthetic Al-hematite, although the crystals become lighter (Munsell value increases) (Barron Torrent, 1984 Kosmas et al, 1986). 

In terms of the Munsell hue (see Chap 6) the colour of red beds varies usually between 5YR-2.5YR (reddish-brown to red), but may also extend into 10RP-7.5RP (red-purple). A more detailed colour measurement using the CIE D a b system places the red beds within a space encircled by a range of synthetic hematites of different crystal sizes, as seen in Figure 15.2. This makes it likely that the colour of red beds is determined by hematite. 

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