1.1 This test method covers the calculation, from instrumentally measured color coordinates based on daylight illumination, of small color differences between nonfluorescent, nonmetameric, opaque specimens such as painted panels. (Where it is suspected that the specimens may be metameric, that is, possess different spectral curves though visually alike in color, Practices D1729 and D4086 should be used to verify instrumental results.) The color differences determined by these procedures are expressed in terms of approximately uniform visual color perception in CIE 1976 CIELAB opponent-color space (1), Hunter L_H,a_H, b_H opponent-color space (2), and the Friele-MacAdam-Chickering (FMC-2) color space (3).

1.2 For product specification, the permissible color difference between test specimen and reference and the procedure for calculating the color difference shall be agreed upon by the purchaser and the seller. Specific color tolerances may be required for each material and condition of use since other appearance factors (for example, 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 problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.