Mottling Assessment of Solid Printed Areas and Its Correlation to Perceived Uniformity

Abstract

Mottling is one of the most important printing defects in modern offset printing using coated papers. Mottling can be defined as undesired unevenness in perceived print density. In our research, we have implemented three methods to evaluate print mottle: the standard method, the cluster-based method, and the bandpass method. Our goal was to study the methods presented in literature, and modify them by taking relevant characteristics of the human visual system into account. For comparisons, we used a test set of 20 grey mottle samples which were assessed by both humans and the modified methods. The results show that when assessing low-contrast unevenness of print, humans have diverse opinions about quality, and none of the methods accurately capture the characteristics of human vision.

Study of no-reference image quality assessment algorithms on printed images

“…32 Moreover, the filter cut-off wavelength is limited by the halftone screen period and should not exceed 0.5 mm, which is the smallest visually disturbing detail from a viewing distance of 30 cm when the unevenness of print is evaluated. 33 In ideal conditions, the acuity limit of the human eye can be as small as 0.017 deg which corresponds to 0.1 mm. 34 It is crucial to select a proper cut-off wavelength that corresponds to an assumed viewing distance and to the ability of a human observer to perceive distortions caused by the halftone pattern.…”

Recycled paper visual indexing for quality control

“…Texture features developed for computer vision applications could provide the visual spatial information needed to characterize this paper sheet defect. We have found some, but not many, precedents of the application of visual pattern recognition techniques in the paper and printing industries: to determine the distribution of local strain during a tensile test (Considine, Scott, Gleisner, & Zhu, 2005), for defect detection in paper pulp images, CalderonMartinez and Campoy-Cervera (2003), for mottling assessment (Sadovnikov, Salmela, Lensu, Kamarainen, & Kalviainen, 1995). Instances of works that report other industrial quality inspection 0957-4174/$ -see front matter Ó 2008 Elsevier Ltd. All rights reserved.…”

“…There are other paper defects that can be modeled using spatial information extracted from images. Computer vision techniques have been used to characterize mottling (Sadovnikov et al, 1995). The mottling defect is due to the uneven distribution of ink, and it is a different phenomenon from the Bumpiness.…”

Comparative study of different methods for the assessment of print mottle

“…One of these effects is print mottle, which is related to density and gloss of print. It is the uneven appearance of solid printed areas, and it depends on the printing toner, paper type and printing process . There are also several definitions of print mottle.…”

“…It is the uneven appearance of solid printed areas, and it depends on the printing toner, paper type and printing process. 3 There are also several definitions of print mottle. Mottling can be defined as undesired unevenness in perceived print density.…”