The Effect of OBA in Paper and Illumination Level on Perceptibility of Printed Colors

A research was conducted to study the perceptibility of color difference of color pairs, caused by OBA differences in paper substrates, and its relationship with quantitative measurement metrics. Based on the psychometric experiments conducted, the results show the utilization of the visual difference index (VDI), from 0 (no difference) to 3 (noticeable difference), to rate 27 color pairs with each pair prepared by the same colorants but different OBA amount in the substrates. The findings indicate that (a) printed colors are affected by the presence of OBA from no difference to noticeable difference, (b) ∆E00 has a stronger linear correlation with visual color difference than ∆E*ab does, (c) there is no significant association between illumination levels and visual color difference. This research introduces the metric, OBA, per ISO 15397 (2013), as the CIE-b* difference in color pairs under M1 and M2 conditions. It also defines ∆OBA as the OBA difference between any color pairs, including substrates. The results show that there is linear correlation (1) between visual difference and ∆E00 which describes the color difference, and (2) between visual difference and ∆OBA which describes the criticalness of M1 lighting to realize the color match.