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    ASTM D2244 - 21

    Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates

    Active Standard ASTM D2244 | Developed by Subcommittee: E12.04

    Book of Standards Volume: 06.01

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    Significance and Use

    5.1 The original CIE color scales based on tristimulus values X, Y, Z and chromaticity coordinates x, y are not uniform visually. Each subsequent color scale based on CIE values has had weighting factors applied to provide some degree of uniformity so that color differences in various regions of color space will be more nearly comparable. On the other hand, color differences obtained for the same specimens evaluated in different color-scale systems are not likely to be identical. 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. There is no simple factor that can be used to convert accurately color differences or color tolerances in one system to difference or tolerance units in another system for all colors of specimens.

    5.2 Color differences calculated in ΔECMC or ΔE00 units are highly recommended for use with color-differences in the range of 0.0 to 5.0 ΔE*ab units. Both are appropriate for and widely used in industrial and commercial applications including, but not limited to, automobiles, coatings, cosmetics, inks, packaging, paints, plastics, printing, security, and textiles. The Hunter color difference components ΔLH, ΔaH, ΔbH, and their color difference unit ΔEH, are used by the coil coating and aluminum extrusion coating industries, as well as the customers of these users. They are, therefore, included in Appendix X1 for historical purposes and use.

    5.3 Users of color tolerance equations have found that, in each system, summation of three, vector color-difference components into a single scalar value is very useful for determining whether a specimen color is within a specified tolerance from a standard. 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. It is possible to include information on the direction of a small color difference by listing the three instrumentally determined components of the color difference.

    5.4 Selection of color tolerances based on instrumental values should be carefully correlated with a visual appraisal of the acceptability of differences in hue, lightness, and saturation obtained by using Practice D1729. 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. That implies that the equations themselves misclassify a color difference with a frequency no greater than that of the most experienced visual color matcher.

    5.5 While color difference equations and color tolerance equations are routinely applied to a wide range of illuminants, they have been derived or optimized, or both, for use under daylight illumination. Good correlation with the visual judgments may not be obtained when the calculations are made with other illuminants. Use of a tolerance equation for other than daylight conditions will require visual confirmation of the level of metamerism in accordance with Practice D4086.

    1. Scope

    1.1 This practice covers the calculation, from instrumentally measured color coordinates based on daylight illumination, of color tolerances and small color differences between opaque specimens such as painted panels, plastic plaques, or textile swatches. Where it is suspected that the specimens may be metameric, that is, possess different spectral curves though visually alike in color, Practice D4086 should be used to verify instrumental results. The tolerances and differences determined by these procedures are expressed in terms of approximately uniform visual color perception in CIE 1976 CIELAB opponent-color space (1)2, CMC tolerance units (2), CIE94 tolerance units (3), the DIN99 color difference formula given in DIN 6176 (4), or the CIEDE2000 color difference units (5).

    1.2 For product specification, the purchaser and the seller shall agree upon the permissible color tolerance between test specimen and reference and the procedure for calculating the color tolerance. Each material and condition of use may require specific color tolerances because other appearance factors, (for example, specimen proximity, gloss, and texture), may affect the correlation between the magnitude of a measured color difference and its commercial acceptability.

    1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

    1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D1729 Practice for Visual Appraisal of Colors and Color Differences of Diffusely-Illuminated Opaque Materials

    D4086 Practice for Visual Evaluation of Metamerism

    E284 Terminology of Appearance

    E308 Practice for Computing the Colors of Objects by Using the CIE System

    E805 Practice for Identification of Instrumental Methods of Color or Color-Difference Measurement of Materials

    E1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation

    Other Standards

    DIN 6176 Farbmetrische, Bestimmung von Farbabstnden bei Krperfarben nach der DIN99-Formel Available from Beuth Verlag GmbH, 10772, Berlin, Germany, http://www.beuth.de/.

    ICS Code

    ICS Number Code 17.180.20 (Colours and measurement of light)

    UNSPSC Code

    UNSPSC Code

    Referencing This Standard
    Link Here
    Link to Active (This link will always route to the current Active version of the standard.)

    DOI: 10.1520/D2244-21

    Citation Format

    ASTM D2244-21, Standard Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates, ASTM International, West Conshohocken, PA, 2021, www.astm.org

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