5.1 This practice should be used whenever measured color-scale or color-difference-scale values are to be compared to an established tolerance. In this way it can be demonstrated quantitatively that the sampling and measurement procedures are adequate to allow an unambiguous decision as to whether or not the mean results are within tolerance.

5.2 This practice assumes that, for the material under consideration and a specified set of color scales, relevant color or color-difference tolerances have been established (see Practice D3134).

5.3 For convenience, the numerical example in the Appendix uses CIELAB LCH (lightness, chroma, hue) color difference scales ΔL*, ΔC*_ab, and ΔH*_ab (see Practice D2244 and Practice E308), but this is not meant to be restrictive.

Note 1: Some coordinates, such as CIE x, y, Y, do not follow the theories of this standard due to excessive collinearity. While it has not been tested, this same collinearity problem may also be observed in 1960 u, v and 1976 u′, v′ coordinates. Table 1 provides a listing of the appropriate and inappropriate color coordinates for use with this practice.

5.4 This practice is based on portions of SAE J 1545, as it applies to painted or plastic automotive parts. It is generally applicable to object colors in various materials. Textured materials, such as textiles, may require special consideration (see SAE J 1545 and STP 15D Manual on Presentation of Data and Control Chart Analysis4).

1.1 Reduction of the variability associated with average color or color-difference measurements of object-color specimens is achieved by statistical analysis of the results of multiple measurements on a single specimen, or by measurement of multiple specimens, whichever is appropriate.

1.2 This practice provides a means for the determination of the number of measurements required to reduce the variability to a predetermined fraction of the relevant color or color-difference tolerances.

1.3 This practice is general in scope rather than specific as to instrument or material.

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.