Yee S. Ng

ISO 19751 macro-uniformity

The ISO WD 19751 macro-uniformity team works towards the development of a standard for evaluation of perceptual image quality of color printers. The team specifically addresses the types of defects that fall in the category of macrouniformity, such as streaks, bands and mottle. The first phase of the standard will establish a visual quality ruler for macro-uniformity, using images with simulated macro-uniformity defects. A set of distinct, parameterized defects has been defined, as well as a method of combining the defects into a single image. The quality ruler will be a set of prints with increasing magnitude of the defect pattern. The paper will discuss the creation and printing of the simulated images, as well as initial tests of subjective evaluations using the ruler.

Recent progress in the development of ISO 19751

A small number of general visual attributes have been recognized as essential in describing image quality. These include micro-uniformity, macro-uniformity, colour rendition, text and line quality, gloss, sharpness, and spatial adjacency or temporal adjacency attributes. The multiple-part International Standard discussed here was initiated by the INCITS W1 committee on the standardization of office equipment to address the need for unambiguously documented procedures and methods, which are widely applicable over the multiple printing technologies employed in office applications, for the appearance-based evaluation of these visually significant image quality attributes of printed image quality. 1,2 The resulting proposed International Standard, for which ISO/IEC WD 19751-13 presents an overview and an outline of the overall procedure and common methods, is based on a proposal that was predicated on the idea that image quality could be described by a small set of broad-based attributes.4 Five ad hoc teams were established (now six since a sharpness team is in the process of being formed) to generate standards for one or more of these image quality attributes. Updates on the colour rendition, text and line quality, and gloss attributes are provided.

INCITS W1.1 development update: appearance-based image quality standards for printers

In September 2000, INCITS W1 (the U.S. representative of ISO/IEC JTC1/SC28, the standardization committee for office equipment) was chartered to develop an appearance-based image quality standard.(1),(2) The resulting W1.1 project is based on a proposal(3) that perceived image quality can be described by a small set of broad-based attributes. There are currently six ad hoc teams, each working towards the development of standards for evaluation of perceptual image quality of color printers for one or more of these image quality attributes. This paper summarizes the work in progress of the teams addressing the attributes of Macro-Uniformity, Colour Rendition, Gloss & Gloss Uniformity, Text & Line Quality and Effective Resolution.

Recent Progress in the Development of INCITS W1.1, Appearance-Based Image Quality Standards for Printers

In September 2000, INCITS W1 (the U.S. representative of ISO/IEC JTC1/SC28, the standardization committee for office equipment) was chartered to develop an appearance-based image quality standard.(1),(2) The resulting W1.1 project is based on a proposal(4) that perceived image quality can be described by a small set of broad-based attributes. There are currently five ad hoc teams, each working towards the development of standards for evaluation of perceptual image quality of color printers for one or more of these image quality attributes. This paper summarizes the work in progress of the teams addressing the attributes of Macro-Uniformity, Color Rendition, Text and Line Quality and Micro-Uniformity.

Gloss uniformity measurement update for ISO/IEC 19751

To address the standardization issues of perceptually based image quality for printing systems, ISO/IEC JTC1/SC28, the standardization committee for office equipment chartered the W1.1 project with the responsibility of drafting a proposal for an international standard for the evaluation of printed image quality1. An ISO draft Standard2, ISO/WD 19751-1, Office Equipment - Appearance-based image quality standards for printers - Part 1: Overview, Procedure and Common Methods, 2004 describes the overview of this multi-part appearance-based image quality standard. One of the ISO 19751 multi-part Standard’s tasks is to address the appearance-based gloss and gloss uniformity issues (in ISO 19751-2). This paper summarizes the current status and technical progress since the last two updates3, 4. In particular, we will be discussion our attempt to include 75 degree gloss (G75) objective measurement5 in differential gloss and within-page gloss uniformity. The result for a round-robin experiment involving objective measurement of differential gloss using G60 and G75 gloss measurement geometry is described. The results for two perceptual-based round-robin experiments relating to haze effect on the perception of gloss, and gloss artifacts (gloss streaks/bands, gloss graininess/mottle) are discussed.

W1.1 macro-uniformity

The INCITS W1.1 macro-uniformity team works towards the development of a standard for evaluation of perceptual image quality of color printers. The team specifically addresses the types of defects that fall in the category of macrouniformity, such as streaks, bands and mottle. This paper provides a brief summary of the status of this work, and describes recent results regarding the precision of the macro-uniformity quality ruler for assessment of typical printer defects.

Differential gloss quality scale experiment update: an appearance-based image quality standard initiative (INCITS W1.1)

Surface characteristics of a printed sample command a parallel group of visual attributes determining perceived image quality beyond color, and they manifest themselves through various perceived gloss features such as differential gloss, gloss granularity, gloss mottle, etc. Extending from the scope of ISO19799 with limited range of gloss level and printing technologies, the objective of this study is to derive an appearance-based differential gloss quality scale ranging from very low gloss level to very high gloss level composed by various printing technology/substrate combinations. Three psychophysical experiment procedures were proposed including the quality ruler method, pair comparison, and interval scaling with two anchor stimuli, where the pair comparison process was subsequently dropped because of the concern of experiment complexity and data consistency after preliminary trial study. In this paper, we will compare the obtained average quality scale after mapping to the sharpness quality ruler with the average perceived differential gloss via the interval scale. Our numerical analysis indicates a general inverse relationship between the perceived image quality and the gloss variation on an image.

INCITS W1.1 macro-uniformity

This paper describes the status of the INCITS W1.1 macro-uniformity ad hoc team, towards development of standards for perceptual image quality for color printers. The team has defined the macro-uniformity attribute, has developed several test patterns to be used for subjective and objective evaluations and has defined test patterns and methods to address color conversions of digitizing devices. A set of print samples, originating from diverse printing systems, has been established, and digitization of these samples is in progress. These activities and next steps are reviewed in this paper.

High-quality LED printhead aging study

In a high quality LED printing system, the non-uniformity of the printhead system not only has to be corrected but maintained over an extended period. To further understand the impact of LED printhead aging on realistic high quality Electrophotographic printing system, we have designed and built a LED printhead aging system and used a 400 dpi printhead to simulate actual printing in a control environment (temperature and drive current). We have pushed this study to an equivalent 40 million pages in printing. A representative image suite for document printing is scanned in and used as the actual printing images. The printhead non-uniformity has been previously corrected before the aging experiment starts. During the aging experiment, the printhead pixel irradiance on the film plane was periodically rescanned radiometrically and the exposure non-uniformity of the printhead using the original correction was calculated and compared with a halftone visual detectability curve. Printhead aging due to realistic image printing usage does not appear to create noticeably observable banding problem even after 40 million pages of simulated printing.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.