A project, supported by the Andrew W. Mellon Foundation, evaluating current practices in fine art image reproduction,
determining the image quality generally achievable, and establishing a suggested framework for art image interchange
was recently completed. (Information regarding the Mellon project and related work may be found at
www.artimaging.rit.edu.) To determine the image quality currently being achieved, experimentation was conducted in
which a set of objective targets and pieces of artwork in various media were imaged by participating museums and
other cultural heritage institutions. Prints and images for display made from the delivered image files at the Rochester
Institute of Technology were used as stimuli in psychometric testing in which observers were asked to evaluate the
prints as reproductions of the original artwork and as stand alone images. The results indicated that there were limited
differences between assessments made with and without the original present for printed reproductions. For displayed
images, the differences were more significant with lower contrast images being ranked lower and higher contrast
images generally ranked higher when the original was not present. This was true for experiments conducted both in a
dimly lit laboratory as well as via the web, indicating that more than viewing conditions were driving this shift.
A project, supported by the Andrew W. Mellon Foundation, is currently underway to evaluate current practices in fine
art image reproduction, determine the image quality generally achievable, and establish a suggested framework for art
image interchange. To determine the image quality currently being achieved, experimentation has been conducted in
which a set of objective targets and pieces of artwork in various media were imaged by participating museums and
other cultural heritage institutions. Prints and images for display made from the delivered image files at the Rochester
Institute of Technology were used as stimuli in psychometric testing in which observers were asked to evaluate the
prints as reproductions of the original artwork and as stand alone images. The results indicated that there were limited
differences between assessments made using displayed images relative to printed reproductions. Further, the
differences between rankings made with and without the original artwork present were much smaller than expected.
KEYWORDS: Image quality, 3D printing, Digital video discs, 3D image processing, Skin, Printing, Visualization, Packaging, Psychology, Advanced distributed simulations
Texture is an important element of the world around us. It can convey information about the object at hand.
Although embossing has been used in a limited way, to enhance the appearance of greeting cards and book covers
for example, texture is something that printed material traditionally lacks. Recently, techniques have been
developed that allow the incorporation of texture in printed material. Prints made using such processes are similar to
traditional 2D prints but have added texture such that a reproduction of an oil painting can have the texture of oil
paint on canvas or a picture of a lizard can actually have the texture of lizard skin. It seems intuitive that the added
dimensionality would add to the perceived quality of the image, but to what degree? To examine the question of the
impact of a third dimension on the perceived quality of printed images, a survey was conducted asking participants
to determine the relative worth of sets of print products. Pairs of print products were created, where one print of each
pair was 2D and the other was the same image with added texture. Using these print pairs, thirty people from the
Rochester Institute of Technology community were surveyed. The participants were shown seven pairs of print
products and asked to rate the relative value of each pair by apportioning a specified amount of money between the
two items according to their perception of what each item was worth. The results indicated that the addition of a
third dimension or texture to the printed images gave a clear boost to the perceived worth of the printed products.
The rating results were 50% higher for the 3D products than the 2D products, with the participants apportioning
approximately 60% of each dollar to the 3D product and 40% to the 2D product. About 80% of the time participants
felt that the 3D items had at least some added value over their 2D counterparts, about 15% of the time, they felt the
products were essentially equivalent in value and 4% of the time they rated the 3D product as having lower value
than the 2D product. The comments of the participants indicated that they were clearly impressed with the 3D
technology and their ratings indicated that they were might be willing to pay more for it, meaning advertisers and
package designers will be interested in using this technology in their products. As 3D printing technology emerges
it will add yet another dimension to the work of print quality analysis.
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.
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.
Common experience indicates the quality of a printed image depends on the choice of the paper used in the printing
process. In the current report, we have used a recently developed device called a micro-goniophotometer to examine
toner on a variety of substrates fused to varying degrees. The results indicate that the relationship between the printed
color gamut and the topography of the substrate paper is a simple one for a color electrophotographic process. If the
toner is fused completely to an equilibrium state with the substrate paper, then the toner conforms to the overall
topographic features of the substrate. For rougher papers, the steeper topographic features are smoothed out by the
toner. The maximum achievable color gamut is limited by the topographic smoothness of the resulting fused surface.
Of course, achieving a fully fused surface at a competitive printing rate with a minimum of power consumption is not
always feasible. However, the only significant factor found to limit the maximum state of fusing and the ultimate
achievable color gamut is the smoothness of the paper.
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.
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 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.
Current color difference metrics such as ΔE*ab, ΔE*94, and ΔE00 were developed using uniformly colored patches. The quantification of color variation in pictorial images is far more complex and generally requires the use of sophisticated color appearance models such as CIECAM97s and CIECAM02. In a recent study of printer color variation, the question was raised as to whether, in certain well-bounded situations, ΔE metrics could be used as a measure of color difference in pictorial, hard-copy images. A psychophysical scaling experiment was designed and conducted to examine this possibility. In the experiment, observers rated test prints of three scenes relative to anchor prints for apparent color difference. The correlation between observer scaling values of color difference for pictorial images and ΔE*ab, ΔE*94, and ΔE00 was examined. It was found that, for the color shifts that were introduced into the test prints under constant media and viewing conditions, the ΔE metrics were effective measures of color variation in pictorial image samples. It was also found, however, that the efficacy of these metrics depended strongly on how the metrics were calculated. The procedure of using colors representative of the important colors in the prints being measured produced significantly better results than other methods of calculating the ΔE metrics.
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