Translucency is a critical property of print on flexible packaging. It forms the basis for obtaining full color gamut, hiding the contents of a package and even creating the scanner readable digital codes for point of purchase tracking. The print industry has followed the paint and decorative coatings industry, the paper industry and the plastics industry in attempting to identify measurement methods that will accurately describe translucency or its opposite, opacity. Both of these properties are defined in terms of the contrast ratio, the ratio of the luminous reflectance of a coating placed over a black and a white substrate. In this paper, the theory of diffuse reflectance spectroscopy is used to define the measurements used to determine the contrast ratio. A brief experimental study illustrates the strong points and weak points of traditional contrast ratio measurements. A better model of contrast ratio determination is hypothesized, and an experiment is designed and reported that demonstrates both the validity of the hypothesis and a method for obtaining consistent estimates of the contrast ratio.

半透明性是软包装印刷的关键特性。它构成了获得全色域、隐藏包裹内容甚至创建用于购买点跟踪的扫描仪可读数字代码的基础。印刷行业紧随油漆和装饰涂料行业、造纸行业和塑料行业，试图确定能够准确描述半透明度或其反面不透明度的测量方法。这两种特性都是根据对比度来定义的，即放置在黑色和白色基材上的涂层的光反射率之比。在本文中，漫反射光谱理论用于定义用于确定对比度的测量值。一个简短的实验研究说明了传统对比度测量的优点和缺点。假设了一个更好的对比度确定模型，并设计并报告了一个实验，该实验证明了假设的有效性和获得一致的对比度估计值的方法。