Quantitative Analysis of Tone Value Reproduction Limits


Document ID: 
Robert Chung and Ping-Hsu Chen


Digital, Non-Member: 
Photo, Member: 
Photo, Non-Member: 


ISO 12647-2 (2004) defines "tone value reproduction limits" requirement as, half-tone dot patterns within 3% to 97% shall transfer onto the print in a consistent and uniform manner, but without a clearly stated test method. This research examines the definition of "tone value reproduction limits" closely and developed a test method that analyzes tone value reproduction limits from an input (tone value) and output (tonality change) point of view. The premise is that the tonalities of specified dots are verified if these dots, when printed, render sufficient tonal differentiation between these dots and their local references. The test method defines highlight contrast in terms of DE*ab between highlights (ranging from 2-10%) and the paper (0%). It defines shadow contrast in terms of DE*ab between shadow dots (ranging from 90-98%) and the solids (100%). In order to determine the tolerance, this research studied a database of 35 offset printed jobs. It was found out that (a) there is a linear relationship between DE*ab and tone values in both highlight and shadow region; and (b) by using the "mean minus one standard deviation" of DE*ab distributions, we can single out or fail one-sixth or 17% of the jobs with low tonality contrast. CIEDE2000 was also tested as a metric for tonal contrast determination, and it did not perform as effective as DE*ab. The proposed test method will improve the usability of the ISO 12647-2 by providing documented  conformance in assessing tone value reproduction limits and can be adopted to specify tone value reproduction limits for other printing process, such as flexography.

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