Color Analysis – CIE94 (ASTM E with ASTM D). Color Analysis – Hunter (ASTM E & ASTM D). Scope: Hunter Lab and XYZ are standard . This standard is issued under the fixed designation D ; the number 1 This practice is under the jurisdiction of ASTM Committee E12 on Color and. ASTM D Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates.
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Examples of Ka and Kb are tabulated in Table X1. The are computed using the following equations: It was derived primarily from visual observations of automotive paints on steel panels. Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm.
This method of computing a metric hue difference loses the information about the sign of the hue difference positive or negative and can be unstable for pairs of colors near the neutral axis.
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It is intended to be used as a single-number shade-passing equation. Validating the specifications, value and safety of your raw materials, products and assets. On the other hand, color differences obtained for the same specimens evaluated in different color-scale systems are not likely to be identical. Lightness L99 5 Under these conditions, Xn, Yn, Zn are the tristimulus values of the standard illuminant with Yn equal to Digital colorimetry allows more tolerance on the spectral scale and spectral bandwidth but demand much more stability in the radiometric scale.
Each material and condition of use may require speci? The X-Rite i7 Colorimeter is highly automated. The sections on apparatus, calibration standards and methods, and measurement procedures served little purpose in the light of modern color-measurement technology. This is contrary to what is observed.
For textiles the following equivalence relations holds: The four color space terms are computed as follows: Each subsequent color scale based on CIE values has 2 6.
Color Analysis – CIE94 (ASTM E with ASTM D)
To avoid confusion, color differences among specimens or the associated tolerances should be compared only when they are obtained for the same color-scale system. While the CIELAB equation has not completely replaced the use of Hunter LH, aH, bH, this older scale is no longer recommended for other than legacy users, and is therefore included in an Appendix for historical purposes. Thus the equation is highly optimized for pairwise comparison of a product standard to a production test specimen but not for statistical process control.
After specifying the illuminant, observer angle, and the reference color, the test sample is inserted into the specimen holder and the spectrophotometer takes the reading. Current edition approved May 1, There should not be a need to break the equation down into perceptual components—the CIELAB components of the model do that already.
Color Analysis – CIE94 (ASTM E1347 with ASTM D2244)
However, for control of color in production, it may be necessary to know not only the magnitude of the departure from standard but also the direction of this departure. For specimens that are matte, randomly rough, or mildly textured, asstm intermediate between 1: Color analysis can be used to match adjacent parts molded from different materials, or to evaluate color change due to outdoor exposure.
Typically a 50 mm 2″ or mm 4″ disk Data: Nor is it possible or reasonable to plot groups of colors in terms of the modi?
Table 2 gives the mean color differences and their standard asm for the groups of instruments considered While not obvious from this listing, all displayed angles are assumed to be given in degrees, including Du and thus must generally be converted into radians for trigonometric analysis on digital computers. If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below.
Send us a request Need help or have a question? Precision and Bias Originally approved in This is convenient for certain textile sorting applications and for graphical quality control charting. Usually, the white object-color stimulus is given by the spectral radiant power of one of the CIE standard illuminants, for example, C, D65 or another phase of daylight, re? The CIELAB color-difference equation is also not recommended in this practice for use in describing small and moderate color differences differences with magnitude less than 5.
Inter-changing the reference and test specimens does not change s2244 the perceived or predicted color differences.
ASTM D – COLOR DETERMINATION
The most common values are 2: They are, therefore, included in Appendix X1 for historical purposes and use. Hunter Lab and XYZ are standard three dimensional color spaces that allows a precise definition of the color of a test sample. Additionally, the colorimetric spectrometer may also be able to report the underlying spectral data from which the colorimetric data were derived. Where it is suspected that the specimens may be metameric, that is, possess different spectral curves though visually alike in color, Practice D should be used to verify instrumental results.
Good correlation with the visual judgments may not be obtained when the calculations are made with other illuminants. All the k values default to 1 in the absence of speci?
The three tolerance equations given here have been tested extensively against such data for textiles and plastics and have been shown to agree with the visual evaluations to within the experimental uncertainty of the visual judgments. The tristimulus values Xn, Yn, Zn de?
There is no simple factor that can be used astk convert accurately color differences or color tolerances in one system to difference or tolerance units in another system for all colors of specimens. Assurance Enabling you to identify and mitigate the intrinsic risk in your operations, supply chains and business processes.
The CMC components and single number tolerances are computed as follows: Thus computed color differences are based only on the Euclidean distance in the DIN99 space.