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
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.
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.<sup>(1),(2)</sup> The resulting W1.1 project is based on a proposal<sup>(4)</sup> that perceived image quality can be described by a small set of broad-based attributes. There are currently five <i>ad hoc</i> 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.
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.
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.
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 an 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 a balance of colorimetric accuracy, in cases where a reference exists, and pleasing overall color appearance. Visual definitions and descriptions of how these sub-attributes are perceived have been developed. The team is presently working to define measurement methods for the sub-attributes, with the focus in 2004 being on color fidelity. This presentation will review the definitions and appearance of the proposed sub-attributes and the progress toward developing test targets and associated measurement methods to quantify the color quantization sub-attribute. The remainder of the discussion will focus on the recent progress made in developing measurement methods for the color fidelity sub-attribute.
The color rendition <i>ad hoc</i> 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.
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.
A common need of the INCITS W1.1 Macro Uniformity, Color Rendition and Micro Uniformity <i>ad hoc</i> efforts is to digitize image quality test targets and derive parameters that correlate with image quality assessments. The digitized data should be in a colorimetric color space such as CIELAB and the process of digitizing will introduce no spatial artifacts that reduce the accuracy of image quality parameters. Input digitizers come in many forms including inexpensive scanners used in the home, a range of sophisticated scanners used for graphic arts and scanners used for scientific and industrial measurements (e.g., microdensitometers). Some of these are capable of digitizing hard copy output for image quality objective metrices, and this report focuses on assessment of high quality flatbed scanners for that role. Digitization using flatbed scanners is attractive because they are relatively inexpensive, easy to use, and most are available with document feeders permitting analysis of a stack of documents with little user interaction. Other authors have addressed using scanners for image quality measurements. This paper focuses (1) on color transformations from RGB to CIELAB and (2) sampling issues and demonstrates that flatbed scanners can have a high level of accuracy for generating accurate, stable images in the CIELAB metric. Previous discussion and experimental results focusing on color conversions had been presented at PICS 2003. This paper reviews the past discussion with some refinement based on recent experiments and extends the analysis into color accuracy verification and sampling issues.
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 <i>ad hoc</i> W1.1 teams, each working on one or more of these image quality attributes. This paper summarizes the work of the W1.1 Microuniformity <i>ad hoc</i> 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).
Color negative films are designed to be intermediate records of photographed objects rather than the final reproduction. Their light absorption serves only to attenuate the printing exposure of another photographic material. They are low gamma, nonviewable films designed to be printed onto high gamma print materials, and the spectral sensitivities of these print materials differ significantly from the human visual system. Input scanners optimized for viewable transmission and reflection materials are not necessarily optimized for color negative films. Their wide exposure latitude and good signal/noise performance result in color negative films being good image capture media. Images having excellent color reproduction, tone scale and image structure characteristics can be extracted from scans of color negative films, but the complexity of recovering optimum pictorial results has resulted in these films being somewhat of an enigma in the desktop publishing and graphic arts arena. The IT8 SC4 committee is in the initial stages of appraising the necessity and considering the specification and design of an input target that would permit calibrated scans to be obtained from color negative films. This paper presents an overview of the negative-positive system and summarizes several specification schemes which could be used as a basis for the design of an IT8 color negative film input calibration target.