Eric K. Zeise

Update on the INCITS W1.1 standard for evaluating the color rendition of printing systems

The color rendition ad hoc team of INCITS W1.1 is working to address issues related to color and tone reproduction for printed output and its perceptual impact on color image quality. The scope of the work includes accuracy of specified colors with emphasis on memory colors, color gamut, and the effective use of tone levels, including issues related to contouring. The team has identified three sub-attributes of color rendition: (1) color quantization -- defined as the ability to merge colors where needed, (2) color scale -- defined as the ability to distinguish color where needed, and (3) color fidelity -- defined as the ability to match colors. Visual definitions and descriptions of how these sub-attributes are perceived have been developed. The team is presently defining measurement methods for these, with the first of the sub-attributes considered being color quantization. More recently, the problem of measuring color fidelity has been undertaken. This presentation will briefly review the definitions and appearance of the proposed sub-attributes. The remainder of the discussion will focus on the progress to date of developing test targets and associated measurement methods to quantify the color quantization and color fidelity sub-attributes.

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.

Scanners for Analytic Print Measurement - the devil in the details

Inexpensive and easy-to-use linear and area-array scanners have frequently substituted as colorimeters and densitometers for low-frequency (i.e., large area) hard copy image measurement. Increasingly, scanners are also being used for high spatial frequency, image microstructure measurements, which were previously reserved for high performance microdensitometers. In this paper we address characteristics of flatbed reflection scanners in the evaluation of print uniformity, geometric distortion, geometric repeatability and the influence of scanner MTF and noise on analytic measurements. Suggestions are made for the specification and evaluation of scanners to be used in print image quality standards that are being developed.

Scanner-based macroscopic color variation estimation

Flatbed scanners have been adopted successfully in the measurement of microscopic image artifacts, such as granularity and mottle, in print samples because of their capability of providing full color, high resolution images. Accurate macroscopic color measurement relies on the use of colorimeters or spectrophotometers to provide a surrogate for human vision. The very different color response characteristics of flatbed scanners from any standard colorimetric response limits the utility of a flatbed scanner as a macroscopic color measuring device. This metamerism constraint can be significantly relaxed if our objective is mainly to quantify the color variations within a printed page or between pages where a small bias in measured colors can be tolerated as long as the color distributions relative to the individual mean values is similar. Two scenarios when converting color from the device RGB color space to a standardized color space such as CIELab are studied in this paper, blind and semi-blind color transformation, depending on the availability of the black channel information. We will show that both approaches offer satisfactory results in quantifying macroscopic color variation across pages while the semi-blind color transformation further provides fairly accurate color prediction capability.

Characteristic measurements for the qualification of reflection scanners in the evaluation of image quality attributes

The claimed specifications of reflection scanners make their utilization for analytic measurement very tempting. This paper summarizes an effort by Working Group 4 of ISO/IEC JTC-1 SC28 to develop evaluation methods that can be used to characterize the performance of reflection scanners with the goal of developing a sufficient characterization set to serve as evaluation methods in conformance testing for future image quality standards. Promising evaluation methods for tone-scale, spatial and temporal uniformity, spatial distortion, SNR, dynamic range and flare characteristics will be described.

Measurement of contributing attributes of perceived printer resolution.

Several measurable image quality attributes contribute to the perceived resolution of a printing system. These contributing attributes include addressability, sharpness, raggedness, spot size, and detail rendition capability. This paper summarizes the development of evaluation methods that will become the basis of ISO 29112, a standard for the objective measurement of monochrome printer resolution.

Characterization of reflection scanner uniformity

A flatbed reflection scanner is a tempting device to use as a surrogate for a microdensitometer in the evaluation of print image quality. Since reflection scanners were never designed with this purpose in mind, many concerns exist regarding their usefulness as a microdensitometer surrogate. This paper addresses the concerns regarding scan uniformity that must be addressed in order to qualify a reflection scanner for use in print image quality evaluation.

Development of ISO/IEC 29112: test charts and methods for measuring monochrome printer resolution

Several measurable image quality attributes contribute to the perceived resolution of a printing system. These contributing attributes include addressability, sharpness, raggedness, spot size, and detail rendition capability. This paper summarizes the development of evaluation methods that will become the basis of ISO 29112, a standard for the objective measurement of monochrome printer resolution.

Update on INCITS W1.1 standard for perceptual evaluation of micro-uniformity

INCITS W1 is the U.S. representative of ISO/IEC JTC1/SC28, the standardization committee for office equipment. In September 2000, INCITS W1 was chartered to develop an appearance-based image quality standard. The resulting W1.1 project is based on a proposal that perceived image quality could be described by a small set of broad-based attributes. There are currently five ad hoc W1.1 teams, each working on one or more of these image quality attributes. This paper summarizes the work of the W1.1 Microuniformity ad hoc team. The agreed-upon process for developing the W1.1 Image Quality of Printers standards is described in a statement located on the INCITS W1.1 web site (ncits.org/tc_home/w11htm/incits_w11.htm), and the process schematic is reproduced here as Figure 1, (in which a final, independent confirmation step has been excluded for brevity).