An Investigation of Factors Influencing Color Tolerances

Tolerance is the permissible difference between sample measurement and the aim and is used to determine the acceptability of a product. A well-known example is the color tolerance of printed solids in ISO 12647-2. The first edition of ISO 12647-2 was published in 1996. It has gone through two major revisions. In the 2004 revision, the magnitude of the color tolerance (?E*_ab) was changed. In the 2013 revision, a new color tolerance metric (?E₀₀) was included. No justification was found regarding the ISO 12647-2 revisions. In this research, %Pass is used to study the effect of color tolerance in a database. Recognizing that tolerance is a man-made decision, if the tolerance is too tight, the %Pass will be low; and vice versa. This research also examines the use of the equal %Pass to determine the tolerance equivalency between the old (?E*_ab) and the new (?E₀₀) parameter. The results show that there is no convergence between ?E*_ab and ?E₀₀ when using the boundary data approach. However, there is an equivalent tolerance between ?E*_ab and ?E₀₀ using the equal %Pass approach. The current ISO 12647-2 standard, using 3.5 ?E₀₀ for CMY and 5 ?E₀₀ for black, resulted in unequal %Pass. By using the equal %Pass approach, the black solid tolerance does not need to be different than cyan and magenta solids, but the yellow solid tolerance can be smaller than cyan and magenta solids.