4.1 Metameric color matches result from the use of different colorants (pigments, dyes, and the like) in achieving the same color match. Usually, the purchaser requires that the color match be nonmetameric; this practice permits this requirement to be quickly tested in both field and laboratory. Where nonmetameric matches are not possible or practicable, for cost or other reasons, some limitation of metamerism may be required. The procedures for estimating the magnitude of metamerism described in this practice provide methods for assessing the effectiveness of such limitation.

1.1 This practice describes visual methods for detecting metamerism and for estimating the magnitude of a metameric color difference.

1.2 The practice is limited to the consideration of illuminant metamerism and observer metamerism. It is not designed to cover so-called geometric metamerism, in which members of specimen pairs change relative appearance as the angles of illumination and viewing are changed, for example, because they incorporate flake metal or pearlescent colorants.

1.3 This practice does not provide for the computation of indices of metamerism based upon instrumental measurement of spectral characteristics.

1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.