Gray Reproduction & Its Conformity Assessment

ISO/TC130 is responsible for international printing standards development. Normative requirements for process control have been centered on solid coloration and TVI. Gray balance and gray reproduction are being addressed in the revision of ISO/WD1 12647-2 (2011). In this regard, the ISO/WD1 12647-2 (2011) takes paper color into consideration when defining gray reproduction aims, but there is a gap in the test method whereby only CIELAB values of the paper and the darkest CMY overprint solid are used to establish the gray reproduction ramp without knowing its relationship to the pre-determined near-neutral triplets and their colorimetric values. This paper takes a top-down approach to address the following issues: (a) what defines printed color, (b) how printing aims, such as gray balance and gray reproduction, are derived, (3) where does substrate correction come in, (4) how to assess gray reproduction of near-neutral triplets, and (5) how to assess gray reproduction conformance.