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  • 1.
    Andersson, Matthias
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kruse, Björn
    The substrate influence on colour measurement2003In: IS&T'S NIP19: INTERNATIONAL CONFERENCE ON DIGITAL PRINTING TECHNOLOGIES, 2003, p. 565-569Conference paper (Refereed)
    Abstract [en]

    The repeatable quality of color image reproduction is a growing challenge for producers of digital printing devices as well as for paper producers. The complex nature of the problem is due to the large number of factors that influence the quality. The properties of the printing substrate such as whiteness, gloss and surface roughness, the colorants and the printing procedure in different combinations together with the proper-ties of the capturing device are all factors that make objective evaluation of print quality very difficult. It is therefore imperative to develop precise methods and routines for color measurement and characterization. In this presentation, the influence of substrate properties on the final printed result will be studied by means of a flatbed digital scanner. The presentation will describe the problems associated with the influence of substrate properties on scanner calibration and will give guidelines for the use of scanners, where large-scale color management control is required. The work reported here is part of an ongoing development of a set of characterization procedures that can be applied to printing situations, consisting of a variety of different printing engines and papers.

  • 2.
    Andersson, Mattias
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Color measurements on prints containing fluorescent whitening agents2007In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2007, Vol. 6493, p. Q4930-Q4950, article id 64930QConference paper (Refereed)
    Abstract [en]

    Papers with a slightly blue shade are, at least among a majority of observers, perceived as whiter than papers having a more neutral color. Therefore, practically all commercially available printing papers contain bluish dyes and fluorescent whitening agents (FWA) to give the paper a whiter appearance. Furthermore, in the Paper Industry, the most frequently used measure for paper whiteness is the CIE-whiteness. The CIE Whiteness formula, does in turn, also favor slightly bluish papers. Excessive examples of high CIE-whiteness values can be observed in the office-paper segment where a high CIE-whiteness value is an important sales argument. As an effect of the FWA, spectrophotometer measurements of optical properties such as paper whiteness are sensitive to the ultraviolet (UV) content of the light source used in the instrument. To address this, the standard spectrophotometers used in the Paper Industry are equipped with an adjustable filter for calibrating the UV-content of the illumination. In the Paper Industry, spectrophotometers with d/0 measurement geometry and a light source of type C are used. The Graphic Arts Industry on the other hand, typically measures with spectrophotometers having 45/0 geometry and a light source of type A. Moreover, these instruments have only limited possibilities to adjust the UV-content by the use of different weighting filters. The standard for color measurements in the Paper Industry governs that measurements should be carried out using D65 standard illumination and the 10 degrees standard observer. The corresponding standard for the Graphic Arts Industry specify D50 standard illumination and the 2 degrees standard observer. In both cases, the standard illuminants are simulated from the original light source by spectral weighting functions. However, the activation of FWA, which will impact the measured spectral reflectance, depends on the actual UV-content of the illumination used. Therefore, comparisons between measurements on substrates containing FWA from two instruments having light sources with different UV-content are complicated. In this study, the effect of FWA content in paper on color reproduction has been quantified for an office-type paper. Furthermore, examples are given on how color measurement instruments give different readings when FWA is present. For the purpose of this study and in order to ensure that only the effect of FWA was observed, a set of papers with varying additions of FWA but otherwise identical, were produced on a small-scale experimental paper machine. The pilot papers were printed in three different printers. Two spectrophotometers representative to the instruments used in the Graphic Arts Industry and the Paper Industry respectively where used to measure the printed papers. The results demonstrate how the use of spectral weighting functions for simulating standard illuminants works properly on non-fluorescent material. However, when FWA is present, disparities in UV content between the light source and the simulated illuminant will result in color differences. Finally, in many printing processes, some of the used inks are UV-blocking, which further complicates the effect of FWA in printed material. An example is shown on how different color differences are obtained for different process ink combinations when the amount of FWA added to the paper is varied.

  • 3.
    Edström, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Pauler, Nils
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Mechanisms involved in the optical interaction between ink and substrate2009In: Advances in Printing and Media Technology, vol 36, International Association of Research Organizations for the Information, Media and Graphic Arts Industrie (IARIGAI), 2009Conference paper (Refereed)
    Abstract [en]

    It is known that colour reproduction of inkjet comprises a range of mechanisms. It was possible to understand and

    explain some of these mechanisms by evaluating print tests with standard optical measurement and by calculations

    using algorithms of the Kubelka Munk and Murray Davies theories. The combined interaction of the substrate, the

    ink penetration, the optical properties of the inks and the dot size were clarified. Large colour gamut is governed by

    low ink penetration, low light scattering of the substrate and small dot size. The non-ideal property of process inks

    and the continuous tone character of colour reproduction of the studied desktop inkjets explained the observed

    convex shape of the colour gamut. For plain paper, dye-based and pigment-based inks were shown to follow different

    mechanisms, with lower penetration of the pigment-based ink. Colour gamut could be increased by a surface

    treatment that further reduced the penetration, but this treatment worked only for the pigment-based inks. Internal

    sizing of plain paper had only a very small influence on colour gamut for dye-based ink, even though the ink

    penetration was reduced.

  • 4.
    Gustafsson Coppel, Ludovic
    et al.
    Norwegian Colour and Visual Computing Laboratory, Gjøvik University College, Gjøvik, Norway.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Lindberg, S.
    Innventia AB, Stockholm, Sweden.
    Impact of illumination spectral power distribution on radiance factor of fluorescing materials2013In: 2013 Colour and Visual Computing Symposium, CVCS 2013, 2013, p. Art. no. 6626275-Conference paper (Refereed)
    Abstract [en]

    The spectral radiance factor and thereby the appearance of fluorescing material is known to depend strongly on the spectral power distribution (SPD) of the illumination in the fluorophore's excitation wavelength band. The present work demonstrates the impact of the SPD in the fluorescence emission band on the total radiance factor. The total radiance factor of a fluorescing paper is measured in three different illuminations. The presence of peaks in the SPD of fluorescent light tubes dramatically decreases the luminescent radiance factor. This effect will impact the appearance of fluorescing media under illuminations with large variation in SPD, which includes recent LED illuminations. © 2013 IEEE.

  • 5.
    Gustafsson Coppel, Ludovic
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lindberg, Siv
    Innventia AB.
    Paper whiteness and its effect on perceived image quality2010In: Final Program and Proceedings - IS and T/SID Color Imaging Conference, The Society for Imaging Science and Technology, 2010, Vol. 50, no 17, p. 62-67Conference paper (Refereed)
    Abstract [en]

    Whiteness is a commercially important characteristic of paper and board, although its perception depends on many factors that often are neglected by instrumental measurements. High whiteness improves the contrast of printed areas and increases the number of reproducible colours, but few quantitative studies have been published. In this paper, we report just-noticeable image quality difference (JND) from pair wise comparisons of images printed on paper substrate of different shades and whiteness. The JND was estimated to approximately 15 CIE whiteness, for the images and whiteness levels in this study, implying that a large substrate whiteness difference is required to get a significant visual impact on image quality. Unlike previous studies limited to colour rendering issues, the influence of the substrate’s shade as a surrounding frame to the images was also investigated here. It was found that the surrounding frame did not have a significant impact on image quality, when the images had an inherent dim background around the objects in the image. However, floating images in which the image objects are adjacent to the unprinted substrate would need further attention, since their perceived image quality seemed to depend both on the colour reproduction related to whiteness and shade, and on the contrast between the image and the substrate.

  • 6.
    Hägglund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Non-destructive high resolution measurements of spatial filler content distribution in paper2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, no 1, p. 131-136Article in journal (Refereed)
    Abstract [en]

    In this work, a non-destructive method is presented that enables the measurement of filler content in paper with high spatial resolution. The method uses an X-ray fluorescence setup that enables high resolution measurements of calcium content in the paper, together with a beta radiography measurement method, to assess the local filler content in the paper. An image registration method is used to combine the two measurement maps, and a calibration polynomial is applied to the point-wise values in order to calculate the local filler content. The measurement methods show good accuracy. The grammage and the calcium content can be measured at a spatial resolution of 0.1 mm × 0.1 mm but the resolution for the filler content map was in this work chosen to 1 mm × 1 mm in order to minimize image registration errors. The method is illustrated using two paper samples, a laboratory paper and a commercial 80 g/m2 copy paper. From the methods used in this work, a difference is shown between the two paper samples in how the filler content distribution is related to the paper formation. With the help of image registration, point-wise measurements of filler content from both sides of the samples can be compared. The method can be used together with other high resolution measurements in order to analyze the simultaneous interrelation between different paper properties. The high resolution measurements of filler content will be particularly valuable for the analysis of the underlying causes to optical variations in paper and print.

  • 7.
    Hägglund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Metsa Board Sverige AB, Husum Mill, SE-89680 Husum, *Sweden.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Umea Univ, SE-90187 Umea, Sweden.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Prediction of optical variations in paper from high resolution measurements of paper properties2013In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 28, no 4, p. 596-601Article in journal (Refereed)
    Abstract [en]

    A method to predict optical variations from high resolution measurementsof paper properties is evaluated in this work. The method combines thepoint-wise values of high resolution maps of filler content and grammagewith an empirical model derived in an earlier study to predict thespatial optical variations in paper.The method has been applied on two paper samples, a laboratory paper anda commercial 80 g/m(2) copy paper. The optical variations have beenpredicted at a scale of 1 mm(2). Validation has been made by using ahigh resolution spectrophotometric setup to measure the spatialreflectance variations in the paper. The results show that for thesamples used, the influence of filler content variations and densityvariations on the optical variations is small compared to influence ofthe grammage variations.

  • 8.
    Hägglund, Håkan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Neuman, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Dependence between paper properties and spectral optical response of uncoated paper2012In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, no 2, p. 440-444Article in journal (Refereed)
    Abstract [en]

    This paper presents a method to describe, with good accuracy, the relation between variations in paper properties and variations of the spectral optical response of an uncoated paper. The dependence between density, filler content, grammage, and the spectral optical response is characterized by a multivariate model. The model is based on large-scale measurements data on a set of paper samples that have been produced with different values of grammage, density and filler content, representing the variations within a normal 80 g/m2 uncoated paper. From the optical measurements the light scattering (s) and light absorption (k) coefficients have been estimated according to the Kubelka-Munk theory.The results from this study will give valuable input to optical modeling activities, where the optical variations are predicted from measured small-scale variations in underlying paper properties.The variations in the paper properties can be used to model the light scattering coefficient, s, but there were too small variations in the light absorption coefficient, k, to find any significant dependence to the paper properties for the samples studied in this work. Furthermore, linear models give sufficient accuracy in the intervals studied. Additional findings from this study are the different effects of wet-pressing and calendering on the light scattering coefficient. 

  • 9.
    Lundberg, Anna
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norberg, Ole
    Voxvil AB, 892 43 Domsjö, Sweden .
    Aggregation of Color pigments by Surface fixation treatment2011In: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 55, no 5, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The quality of a printed image is strongly influenced by the physical and the chemical interactions between the ink and the paper. Print quality can be evaluated either by objective measurements using instruments or by visual assessment studies involving panel of observers judging the final print. In this article, the print quality on commercial papers as well as on non-commercial papers with different amounts of salt for surface fixation has been studied. Perceived detail reproduction depends not only on sharp edge definition but also on the level of color saturation (Chroma). Color saturation and edge definition originate from two different ink and paper interaction processes. Color saturation is heavily dependent on ink penetration while edge definition correlates to ink spreading. In order to gain understanding of the performance of surface treatment by salt, large efforts have been put on splitting up of the increase in color saturation (Chroma) and improved edge definition. The printouts have been made with a desktop printer using pigmented inks. Cross section images have been taken with a light microscope to analyze the ink penetration depth. SEM analysis has been made to analyze the aggregation of the pigments on the surface. The print quality measurements have been both objective measurements such as print density and subjective image evaluation using a test panel of observers in a perceptual study. The perceptual study focused on detail reproduction, and efforts were made to separate the influence of the print density from the edge definition on the detail reproduction. The result from this study shows that an increased level of salt as surface fixation improves the detail reproduction due to aggregation of the pigments on the surface and that the ink penetration depth can be reduced by adding salt as surface fixation resulting in a higher print density.

  • 10.
    Lundberg, Anna
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Wågberg, K
    Improved Print quality by Surface fixation of Pigments2010In: International Conference on Digital Printing Technologies, The Society for Imaging Science and Technology, 2010, , p. 5p. 251-255Conference paper (Refereed)
    Abstract [en]

    Inkjet printing is a non impact printing method that deposits a limited amount of ink onto the paper surface. To improve runnabillity and printability the demands on papers ability to rapidly absorb the fluid and make the colorants stay on the surface increase. These demands get more pronounced as the technology develops and the print speed significantly increases.

    The quality of a printed image is strongly influenced by the physical and the chemical interactions between the ink and the paper. Some print quality parameters can be measured objectively by physical measurements using instruments. Subjective print quality evaluation involves human judgments of the final print.

    In this article, the print quality on commercial papers as well as on trial papers with different amounts of salt for surface fixation has been studied. The printouts have been made with a desktop printer that uses pigmented inks. The print quality measurements have been both objective measurements such as print density and line quality and subjective image evaluation using a test panel in a perceptual study. The perceptual study focused on detail reproduction, and efforts were made to separate the influence of the print density from the edge definition on the detail reproduction. The study confirms the influence of ink and paper interaction on print quality and the relation to different levels of surface fixation.

  • 11.
    Neuman, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Coppel, Ludovic
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Angular Variations of Color in Turbid Media – the Influence of Bulk Scattering on Goniochromism in Paper2010In: 5th European Conference on Colour in Graphics, Imaging, and Vision and 12th International Symposium on Multispectral Colour Science 2010, CGIV 2010/MCS'10, 2010, p. 407-413Conference paper (Refereed)
    Abstract [en]

    The angular variations of color of a set of paper samples are  experimentally assessed using goniophotometric measurements.  The corresponding simulations are done using a radiative transfer based simulation tool, thus considering only the contribution  of bulk scattering to the reflectance. It is seen that measurements  and simulations agree and display the same characteristics, with  the lightness increasing and the chroma decreasing as the observation  polar angle increases. The decrease in chroma is larger  the more dye the paper contains. Based on previous results about  anisotropic reflectance from turbid media these findings are explained.  The relative reflectance in large polar angles of wavelengths  with strong absorption is higher than that of wavelengths  with low absorption. This leads to a loss of chroma and color information  in these angles. The increase in lightness is a result  of the anisotropy affecting all wavelengths equally, which is the  case for transmitting media and obliquely incident illumination.  The only case with no color variations of this kind is when a nonabsorbing,  non-transmitting medium is illuminated diffusely. The  measured and simulated color differences are clearly large, and  it is an open issue how angle resolved color should be handled  in standard color calculations.

  • 12.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Improvement of home and office printing by paper ICC-profiles2005In: 2005 Beijing International Conference on Imaging: Technology and Applications for the 21st Century, BEIJING: Science Press, 2005, p. 226-227Conference paper (Refereed)
    Abstract [en]

    Accurate characterisation of paper and printer are needed to achieve consistent color reproduction in digital printing. The output ICC profile data depends on such as the ink, halftoning method and paper properties paper If anyone of these parameters is changed, the generation of a new ICC profile must be considered. In home and office environments, where the user cannot be expected to create a profile himself, users are limited to the profiles usually shipped with the device. The color reproduction of desktop printers can be improved by paper specific profiles. In this work, a method to include the influence of paper properties without generating a new profile is also proposed. The method is based on a printer module describing the printer characteristics and a additional module that takes paper properties into account. With this approach, no color measuring devices or profile generating software are needed. In this study the potential of paper specific ICC-profile has been examined. The result show significant improvement in both colour accuracy and perceived image quality.

  • 13.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Paper whiteness and its effect on the reproduction of colors2007In: Human Vision and Electronic Imaging XII, SPIE - International Society for Optical Engineering, 2007, p. 64920V-Conference paper (Refereed)
    Abstract [en]

    The whiteness level of a printing paper is considered as an important quality measure. High paper whiteness improves the contrast to printed areas providing a more distinct appearance of printed text and colors and increases the number of reproducible colors. Its influence on perceived color rendering quality is however not completely explained. The intuitive interpretation of paper whiteness is a material with high light reflection for all wavelengths in the visual part of the color spectrum. However, a slightly bluish shade is perceived as being whiter than a neutral white. Accordingly, papers with high whiteness values incline toward bluish-white. In paper production, a high whiteness level is achieved by the use of highly bleached pulp together with high light scattering filler pigment. To further increase whiteness levels expensive additives such as Fluorescent Whitening Agents (FWA) and shading dyes are needed. During the last years, the CIE whiteness level of some commercial available office paper has exceeded 170 CIE units, a level that can only be reached by the addition of significant amounts of FWA. Although paper whiteness is considered as an important paper quality criterion, its influence on printed color images is complicated. The dynamic mechanisms of the human visual system strive to optimize the visual response to each particular viewing condition. One of these mechanisms is chromatic adaptation, where colored objects get the same appearance under different light sources, i.e. a white paper appears white under tungsten, fluorescent and day light. In the process of judging printed color images, paper whiteness will be part of the chromatic adaptation. This implies that variations in paper whiteness would be discounted by the human visual system. On the other hand, high paper whiteness improves the contrast as well as the color gamut, both important parameters for the perceived color reproduction quality. In order to quantify the influence of paper whiteness pilot papers with different amount of FWA but in all other respects similar were produced on a small scale experimental paper machine. The fact that only the FWA content changes reduces the influences of other properties separated from the paper whiteness in the evaluation process. A set of images, all having characteristics with the potential to reveal the influence of the varied whiteness level on color reproduction quality, were printed on the pilot papers in two different printers. Prior to printing the test images in the experiment, ICC-profiles were calculated for all the used printer-substrate combinations. A visual assessment study of the printed samples was carried out in order to relate the influence of the paper whiteness level to perceived color reproduction quality. The results show an improved color rendering quality with increased CIE whiteness value up to a certain level. Any further increase in paper whiteness does not contribute to an improved color reproduction quality. Furthermore, the fact that some printing inks are UV blocking while others are not will introduce a non uniform color shift in the printed image when the FWA activation changes. This non uniform color shift has been quantified both for variations in illuminant as well as variations of FWA content in the paper.

  • 14.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Paper Whiteness vs Reproduction of Colour2009In: Optical Brighteners & Paper Whiteness Conference, 2009, London, UK, 2009Conference paper (Other academic)
  • 15.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    The Influence of Paper Properties in Color Inkjet Printing2005In: European Coating Conference, 2005, Berlin, Germany: Inkjet Material, 2005Conference paper (Other academic)
  • 16.
    Norberg, Ole
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Andersson, M
    Perceived image quality of printed images and their relation to paper properties2009In: Final Program and Proceedings - IS and T/SID Color Imaging Conference 2009, The Society for Imaging Science and Technology, 2009, p. 210-215Conference paper (Refereed)
    Abstract [en]

    In printing the final color image reproduction quality depends on the quality of the digital image as well as the properties of the printing system and the paper used. Although it is well known that the paper has a large influence on the print result it is seldom specified according to image quality attributes. Computer screens, digital cameras and printers are all technically specified with respect to resolution (number of pixels and dots per inch), gradation (bit depths) and primary color channels. The technical specification of paper on the other hand mainly includes properties of the unprinted paper that provide limited information about the appearance of the printed image. However, the characterization of paper is not as straight forward as the performance is not only related to the paper properties but also to a high extent to its interaction with the printing system. One way to indicate the color reproduction quality of images is to determine the modular transfer function (MTF). Several studies have derived the MTF of paper for certain printing situations (Bouzit 2002, Koopipat 2000 and Rogers 2000) and stated the influenced of not only the physical properties of the paper but also by the interaction between paper and ink. The most decisive properties found on paper MTF are ink penetration, ink spreading and the optical properties of the paper. Moreover, these paper properties can be associated to color rendering attribute associated with image quality such as color gradation, color gamut volume and image sharpness. In this study, these three attributes have been varied prior to printing in two sets of test images representing office paper and photo inkjet paper respectively. Color gamut volume, color gradation and sharpness were varied simultaneously according to a statistical experimental design thus producing a subset of modified versions for each image in the test set. Furthermore, a visual assessment study was carried out in order to study the effect of the modifications on the perceived impression of the printed images. Finally, the data from the visual assessment study was analyzed in order to reveal how the different attributes influenced the perceived color rendition. The results from the study showed that small changes in the varied attributes produces large response on the perceived color rendering quality and that the most important parameter is color gamut volume.

  • 17.
    Norberg, Ole
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Andersson, Matthias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kruse, Björn
    The influences of paper properties on color reproduction and color management2003In: IS&T'S NIP19: INTERNATIONAL CONFERENCE ON DIGITAL PRINTING TECHNOLOGIES, 2003, p. 836-840Conference paper (Refereed)
    Abstract [en]

    The characterization of the transfer function of a printing device is a complex procedure involving not only the device itself but also the paper and its properties. The work reported here is an ongoing development of building a library of characterization procedures. These procedures can be applied to printing situations with different combinations of printing engines and paper grades. An example of a building block is color separation with respect to halftoning techniques and available inks or toners. Another is the characterization of the physical properties of the paper substrate. The most common characterization procedure is through the ICC-profile. Device ICC-profiles contain the data needed for a color management system (CMS) to do color separation and the color mapping. In this study special emphasis is put on the influence of the paper properties and on how they affect the profile. Gloss, surface roughness, whiteness and light scattering are all measurable paper properties that certainly will affect the color reproduction. Ink and paper interaction and especially ink penetration is also a phenomena that affect the color reproduction and thus the ICC profile.

  • 18.
    Norberg, Ole
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Colour Gamuts - Is size the only thing that matters?2006In: Proceedings of the Technical Association of the Graphic Arts, TAGA, 2006, Vol. 2006, p. 273-281Conference paper (Refereed)
    Abstract [en]

    Today's Inkjet printers are capable of producing colour images of very high quality. However, in inkjet printing, the substrate has a large influence on the quality of a printed image. In addition, the large variety of inkjet substrates increases the complexity of the colour reproduction in inkjet printers. Even when high-quality substrates are used, colour management is required when the input data is represented in any of the RGB colour spaces used today. Moreover, colour gamut transformations are inherent as the colour gamut of colour reproduction systems differ in size and shape. In this study, three colour rendering attributes associated with image quality - colour gradation, colour gamut volume and sharpness have been varied prior to printing in a set of test images. In real life, variations in these colour rendition attributes can be caused by different substrate properties, inappropriate printer settings for a specific substrate or the result of shortcomings in colour management. Whatever the cause may be, the effects of these variations can be observed in inkjet-printed images. The colour gamut volume, colour gradation and sharpness were varied simultaneously according to a statistical experimental design thus producing a subset of modified versions for each image in the test set. Furthermore, a visual assessment study was carried out in order to study the effect of the modifications on the perceived impression of the colour rendition in the printed images. Finally, the data from the visual assessment study was analysed in order to reveal how the different attributes influenced the perceived colour rendition.

  • 19.
    Norberg, Ole
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Andersson, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Focusing on Paper Properties in Color Characterization of Printing Situations2002In: NIP18: International Conference on Digital Printing Technologies, 2002, p. 774-776Conference paper (Refereed)
    Abstract [en]

    procedure involving not only the paper itself but also the various printers used. In a situation where the number of printing devices grows rapidly, there is a need for an efficient characterization procedure. The work reported here is an ongoing development of building a library of characterization procedures. These procedures can be applied to printing situations with different combinations of paper grades and printing engines. Special emphasis is put on the influence of the paper properties. Color characterization of printing devices is normally performed using color charts based on different combinations of process colors. These charts are often adapted to certain printing technologies. For an example, the IT8 color chart works well for offset printing but is certainly not optimal in all digital printing situations. The starting point in this development is the selection of a set of equidistant percepts from a homogenous color space. An example of a building block is color separation with respect to halftoning techniques and available inks or toners. Another is the characterization of the physical properties of the paper substrate.

    The result of the new procedure for color characterization of printing papers correlates with existing methods. It has also contributed to a deeper understanding of the large influence paper has on the final print quality.

  • 20.
    Norberg, Ole
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Westin, P
    Framkom, Stockholm.
    Lindberg, S
    STFI, Stockholm.
    Klaman, M
    Framkom, Stockholm.
    Eidenvall, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A comparison of print quality between digital and traditional technologies2001In: IS&T’S INTERNATIONAL CONFERENCE ON DIGITAL PRODUCTION PRINTING AND INDUSTRIAL APPLICATIONS, Springfield: SOCIETY IMAGING SCIENCE TECHNOLOGY , 2001, p. 380-385Conference paper (Other academic)
    Abstract [en]

    The digital print technologies are advancing both in quality and market share. Today, the print quality of digital printed material has improved and is considered to bee good enough for most purposes. However, the great advantages of digital printing are short runs and variable data printing. In this investigation the print quality of different digital printing technologies, today present on the market, are compared with the quality of traditional technologies such as offset and flexography. A wide range of digital presses, from large production presses to smaller devices for office use, was tested. The substrates used, were all chosen to fit the specific printing technology. The print quality was evaluated by subjective evaluation as well as by technical measurements. To make the comparison of prints from different presses meaningful, color management has been an essential part of the process. An ICC-profile was created for each combination of substrate and press. The results indicate that the offset print quality on fully coated paper is still ahead of what is possible to achieve with digital printing techniques today. This study shows that disturbance, like mottling and gloss variation, are the main shortcomings of the digital printing technologies. Another result, shown in this study, is the fact that digital printing is less sensitive to type of substrate.

  • 21.
    Rahaman, G M Atiqur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Extension of Murray-Davies tone reproduction model by adding edge effect of halftone dots2014In: Proceedings of SPIE - The International Society for Optical Engineering, San Francisco, California, United States: SPIE - International Society for Optical Engineering, 2014, p. Art. no. 90180F-Conference paper (Refereed)
    Abstract [en]

    We propose expanding the Murray-Davies formula by adding the effect of edges of solid inks in a halftoned image. The expanded formula takes into account the spectral reflectance of paper white, full tone ink and mixed area scaled by the fractional area coverages. Here, mixed area mainly refers to the edge of an inked dot where the density is very low, and lateral exchange of photons can occur. Also, in such area the paper micro components may have higher scattering power than ink, especially, in uncoated paper. Our methodology uses cyan, magenta and yellow separation ramps printed on different papers by impact and non-impact based printing technologies. The samples include both frequency and amplitude modulation halftoning methods of various print resolutions. Based on pixel values, the captured microscale halftoned image is divided into three categories: solid ink, mixed area, and unprinted paper between the dots. The segmented images are then used to measure the fractional area coverage that the model receives as parameters. We have derived the characteristic reflectance spectrum of mixed area by rearranging the expanded formula and replacing the predicted term with the measured value using half of the maximum colorant coverage. Performance has clearly improved over the Murray-Davies model with and without dot gain compensation, more importantly, preserving the linear additivity of reflectance of the classical physics-based model.

  • 22.
    Rahaman, G M Atiqur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Microscale halftone color image analysis: perspective of spectral color prediction modeling2014In: Proceedings of SPIE - The International Society for Optical Engineering: Color Imaging XIX: Displaying, Processing, Hardcopy, and Applications, San Francisco, California, United States: SPIE - International Society for Optical Engineering, 2014, p. Art. no. 901506-Conference paper (Refereed)
    Abstract [en]

    A method has been proposed, whereby k-means clustering technique is applied to segment microscale single color halftone image into three components—solid ink, ink/paper mixed area and unprinted paper. The method has been evaluated using impact (offset) and non-impact (electro-photography) based single color prints halftoned by amplitude modulation (AM) and frequency modulation (FM) technique. The print samples have also included a range of variations in paper substrates. The colors of segmented regions have been analyzed in CIELAB color space to reveal the variations, in particular those present in mixed regions. The statistics of intensity distribution in the segmented areas have been utilized to derive expressions that can be used to calculate simple thresholds. However, the segmented results have been employed to study dot gain in comparison with traditional estimation technique using Murray-Davies formula. The performance of halftone reflectance prediction by spectral Murray-Davies model has been reported using estimated and measured parameters. Finally, a general idea has been proposed to expand the classical Murray-Davies model based on experimetal observations. Hence, the present study primarily presents the outcome of experimental efforts to characterize halftone print media interactions in respect to the color prediction models. Currently, most regression-based color prediction models rely on mathematical optimization to estimate the parameters using measured average reflectance of a large area compared to the dot size. While this general approach has been accepted as a useful tool, experimental investigations can enhance understanding of the physical processes and facilitate exploration of new modeling strategies. Furthermore, reported findings may help reduce the required number of samples that are printed and measured in the process of multichannel printer characterization and calibration.

  • 23.
    Rahaman, G M Atiqur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Edström, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    The effect of media interactions in predicting spectral reflectance by color prediction models2013Conference paper (Refereed)
  • 24.
    Rahaman, G M Atiqur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Parkkinen, Jussi
    School of Engineering, Monash University, Sunway Campus, Malaysia.
    Hauta-Kasari, Markku
    SIB Labs., School of Computing, University of Eastern Finland, Finland.
    Norberg, Ole
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Retinal Spectral Image Analysis Methods using Spectral Reflectance Pattern Recognition2013In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Berlin Heidelberg: Springer, 2013, Vol. 7786, p. 224-238Conference paper (Refereed)
    Abstract [en]

    Conventional 3-channel color images have limited information andquality dependency on parametric conditions. Hence, spectral imaging andreproduction is desired in many color applications to record and reproduce thereflectance of objects. Likewise RGB images lack sufficient information tosuccessfully analyze diabetic retinopathy. In this case, spectral imaging may bethe alternative solution. In this article, we propose a new supervised techniqueto detect and classify the abnormal lesions in retinal spectral reflectance imagesaffected by diabetes. The technique employs both stochastic and deterministicspectral similarity measures to match the desired reflectance pattern. At first, itclassifies a pixel as normal or abnormal depending on the probabilistic behaviorof training spectra. The final decision is made evaluating the geometricsimilarity. We assessed several multispectral object detection methodsdeveloped for other applications. They could not proof to be the solution. Theresults were interpreted using receiver operating characteristics (ROC) curvesanalysis.

1 - 24 of 24
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