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Back Trap and Half-tone Mottle Measurement With Stochastic Frequency Distribution Analysis

An excerpt from the paper

A spatially sensitive stochastic frequency distribution analysis software algorithm, operating in a graphic arts quality scanner based image analysis system, has been applied to offset printed images. This algorithm is based upon the luminance value statistical variance within a target that is “tiled” in the image as opposed to other less reproducible techniques that employ the average of the luminance values. The algorithm is sensitive to the spatial distribution and relative size of skipped and lightly printed sub-visible areas that are correlated to half-tone mottle. It has been discovered the separation and arithmetic recombination of the digital image color bands used to acquire the digital image can be used to amplify the variances in different colored inks. Several examples of this method in use are provided with illustrations and a suggested measurement scale.

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mottle.pdf