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Toward better image reproduction in offset
KTH, School of Computer Science and Communication (CSC), Media Technology and Graphic Arts, Media.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis has focused on color reproduction processes in the graphics field and is based on theoretical research and practical studies. The purpose of this thesis was to investigate how new tools and tools adapted to a specific production set-up can be used to raise awareness regarding the quality and workflow of images and image processing for sheet-fed offset within the graphic industry.

The work is divided in to the following three study areas with several sub-studies:

1) The first research goal of the thesis is to identify knowledge levels regarding color separation of images and demand specifications within printing houses.

2) The second research goal is to investigate whether novel tools and new terminology can help to increase the knowledge level regarding color management

3) The third goal is to investigate whether process specific adaptation of key color control tools can improve quality levels

Three surveys about color reproduction (focusing on level of knowledge concerning color separation, the use of ICC-profiles and demand specifications for controlled color reproduction) at printing companies in Sweden were made between 2000 and 2004. The surveys indicated a serious problem in the graphic arts industry, involving both an insufficient understanding of color management and a lack of communication.

An important part of the work was to assist in make color management understandable for users and thereby optimize printing. For this purpose, digital test forms have been developed. The developed tools, together with descriptive material, will facilitate the understanding of color management issues. Definitions within the field of color separations have been examined, and changes have been suggested. A new term for separation “Compensation by Black”, CB, has been suggested, instead of e.g. GCR and UCR.

Is it possible to adapt the different parts of the process chain in order to achieve an improved production? Yes! This work has developed the method for adaptation of the scanne rtest chart, the printing test chart for image categorization and the control strip forsheet-fed offset using gray balance. This thesis suggests that it is possible to produce a custom-made IT8 target test chart for scanners and achieve a result at least similar to or even better than the standard test charts on the market. This work has also shown that itis possible to adapt the test chart for printing to image category. The result showed that low-key image separated by the image-adapted test chart showed more detail in the dark areas than a low-key image separated by the standard test chart, in the prints on a coated paper. The result from the adaptation of a control strip for sheet-fed offset showed that gray balance can be used as a control parameter for quality control in sheet-fed offset.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , 133 p.
Series
Trita-CSC-A, ISSN 1653-5723 ; 2010:06
Keyword [en]
Images, offset, printing, ICC, color, gamut, profile, calibration, separation, GCR, UCR, characterization, gray balance
National Category
Computer Science Media and Communications
Identifiers
URN: urn:nbn:se:kth:diva-12432ISBN: 978-91-7415-609-6 (print)OAI: oai:DiVA.org:kth-12432DiVA: diva2:311490
Public defence
2010-05-03, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100617Available from: 2010-04-21 Created: 2010-04-21 Last updated: 2010-08-26Bibliographically approved
List of papers
1. Image classification and optimized image reproduction
Open this publication in new window or tab >>Image classification and optimized image reproduction
2003 (English)In: TAGA 2003, 2003, 33-36 p.Conference paper, Published paper (Refereed)
Abstract [en]

New adapted color charts have been created based on technical and visual image category analysis. A number of tests have been carried out using extreme images with their key information strictly in dark and light areas. It was shown that the image categorization using the adapted color charts improves the analysis of relevant image information with regard to both the image gradation and the detail reproduction. The images with key information in hi-key areas were also test printed using the adapted color charts.

Keyword
characterization, conversion, ICC, profiling. reproduction
Identifiers
urn:nbn:se:kth:diva-6571 (URN)
Note
QC20100617Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-06-17Bibliographically approved
2. The characterization of input devices by luminance and chrominance
Open this publication in new window or tab >>The characterization of input devices by luminance and chrominance
2003 (English)In: Polygraficky seminar, 2003, 2003, 10- p.Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:kth:diva-6572 (URN)
Note
QC20100617Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-06-17Bibliographically approved
3. Image reproduction practices
Open this publication in new window or tab >>Image reproduction practices
2004 (English)In: TAGA 2004, 2004, 318-331 p.Conference paper, Published paper (Refereed)
Abstract [en]

Various aspects of image reproduction practices are discussed. The main aim is to simplify image reproduction by implementing a common color language and using a color matching method suitable for the reproduction. To achieve optimized reproduction certain requirements are to be fulfilled mainly knowledge in basic color theory and training in the color reproduction process. Moreover, it is important to have better access to applicable research results in an understandable language and better understanding of available ICC profiling tools and systems on the market.

Keyword
Color; ICC; Management; Problems; Separation
Identifiers
urn:nbn:se:kth:diva-6573 (URN)2-s2.0-23244464407 (Scopus ID)
Note
QC20100617Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-06-17Bibliographically approved
4. Digital test form for ICC-profiles
Open this publication in new window or tab >>Digital test form for ICC-profiles
2005 (English)In: TAGA 2005, 2005, 454-473 p.Conference paper, Published paper (Refereed)
Abstract [en]

The majority of Swedish offset printers use color management in order to control color reproduction in their daily production. However, there is a lack of understanding of how well the profiles support agreement among color units. Several parameters in the construction and use of a profile affect the final color result. Print production using ICC-profiles demands a better teamwork in the process. The use of non-dedicated printer profiles may cause a less than optimal end-result. Pedagogic color tools can help the user to understand how well a specific profile defines the color gamut of a digital/analogue printingpress. This paper presents an approach to visualizing how well printer profile parameters are defined in the construction of the ICC-profile. The application Adobe Photoshop ® has been used for profile evaluation because of its widespread use in the graphic arts field. A digital test form has been produced consisting of color test targets and images. This digital test form can give information about: 1) differences between color gamuts, e.g. ECl-RGB, ColorMatch 2) total ink coverage 3) the level of achromatic reproduction, GCR, UCR (Gray Component Replacement, Under Color Removal) 4) effect on different tones, e.g. skin tones 5) comparison between different print profiles and the ISO standard - gamut warning 6) gamut mapping 7) different rendering methods 8) chroma shift when converting to CMYK 9) control of gray balance 10) control of color settings in the applications - ProfileMaker and Print Open The basic model is made from a number of color patches forming a uniform matrix pattern. The matrix construction was created in Adobe Illustrator and Adobe Photoshop. The testform is built in the RGB-color mode, using the standardized color working space, ECI-RGB. To achieve an even distribution of lightness and saturation in the matrix, the HSB (Hue, Saturation and Brightness) color model was chosen. Moving from one patch to the next represents a change in saturation and lightness by ten percent. The colors red and cyan, green and magenta, blue and yellow are confronted to each other as a result of their relationship as complement colors. The center point of the model holds a gray scale built from equal amounts of red, green and blue parts in the RGB-mode. The base model contains information about the total ink coverage (%) and control of color cast. Each matrix has been complemented with a color wise corresponding image to enhance the color conversion change. These images have also been divided into a mosaic pattern to enable measurements directly on the images. This digital test form for ICC-profiles has been evaluated by eight independent graphic arts consultants who work with the implementation of ICC-based production. The result of this evaluation is a recommendation for the printers to use this digital test form to increase awareness of the influence of ICC-profiles on the print.

Keyword
Communication; Conversion; Education; ICC; Separation
Identifiers
urn:nbn:se:kth:diva-6574 (URN)
Note
QC20100617Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-06-17Bibliographically approved
5. Demand specifications for controlled color reproduction
Open this publication in new window or tab >>Demand specifications for controlled color reproduction
2005 (English)In: VII International Seminar in Graphic Arts, 2005, 11- p.Conference paper, Published paper (Refereed)
Identifiers
urn:nbn:se:kth:diva-6575 (URN)
Note
QC20100617Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-06-17Bibliographically approved
6. Compensation by black: a new separation?
Open this publication in new window or tab >>Compensation by black: a new separation?
2006 (English)In: TAGA 2006, 2006, 193-217 p.Conference paper, Published paper (Refereed)
Abstract [en]

The aim of this paper is to examine the differences between UCR (Under Color Removal) and GCR (Gray Component Replacement) by testing these separation functions in three applications: Adobe Photoshop CS (an image editing application), Gretag Macbeth's Profile Maker 5.0 (profile maker), and Heidelberg's Print Open 4.0.5 (profile maker). A review of the literature pertaining to the different types of separation was made and compiled. An Internet search was also made to check what a prepress employee would find out if he or she was to search for a definition of one of these types of separation. The conclusions of the tests made suggest two alternative proposals and indicate a need to either: 1) Discard the term UCR and use only GCR, as it really only concerns gray component replacement. This would make it easier for people in the business to focus on the process itself instead of trying to understand the difference between the two types of separations, a difference which actually cannot be seen visualy in reality. 2) Discard both terms and introduce a new term CB (Compensation by Black). The software should give the user the possibility of choosing how much black will be used and where it will replace the use of a combination of the CMY process colors. In addition, a single term would make the user more aware of the problems of separation and of how separation will affect the print result. The suggestions imply an extensive review of accepted terms and abbreviations within the graphic arts industry with the aim of giving them a uniform scientific meaning and definition. Thus, it is strongly recommended that the term, CB (Compensation by Black) should be implemented.

Keyword
Compensation; GCR; Separation; UCR
National Category
Media and Communications
Identifiers
urn:nbn:se:kth:diva-6576 (URN)
Conference
58th Annual Technical Conference of the Technical Association of the Graphic Arts, TAGA 2006; Vancouver, BC; 19 March 2006 through 21 March 2006
Note
QC 20100617Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2010-06-29Bibliographically approved
7. Using gray-balance control in press calibration for robust ICC color management in sheet-fed offset
Open this publication in new window or tab >>Using gray-balance control in press calibration for robust ICC color management in sheet-fed offset
2004 (English)In: Proceedings of the Technical Association of the Graphic Arts, TAGA, 2004, 1-20 p.Conference paper, Published paper (Refereed)
Abstract [en]

The use of gray-balance control in press calibration for robust ICC color management in sheet-fed offset is discussed. Gray-balance control is a way to calibrate printing presses. It is found possible to print without a color cast, and still keep print contrast, density, dot gain and CIELAB values for the secondary colors at an acceptable level. It is shown that the ICC profile can give a similar print quality on different papers.

Keyword
Balance, Gray, Offset, Sheetfed, Stability
National Category
Media and Communication Technology
Identifiers
urn:nbn:se:kth:diva-6577 (URN)2-s2.0-23244447404 (Scopus ID)
Conference
56th Annual Technical Conference of the Technical Association of the Graphic Arts, TAGA 2004; San Antonio, TX; United States; 20 April 2004 through 20 April 2004
Note

QC 20100617

Available from: 2006-12-12 Created: 2006-12-12 Last updated: 2014-12-09Bibliographically approved
8. Gray Balance Control in Sheet-Fed Offset Printing
Open this publication in new window or tab >>Gray Balance Control in Sheet-Fed Offset Printing
2008 (English)In: Proceedings of the Technical Association of the Graphic Arts, TAGA, 2008, -176 p.Conference paper, Published paper (Refereed)
Abstract [en]

Newspaper printing can be controlled by visual gray balance assessment, a procedure which is widespread among newspaper printers in Sweden. In sheet-fed offset today, there is no fast and efficient way to process control the sheet-fed offset-press during production without using advanced online-systems. The control patches which are used in sheet-fed offset during the production often lack the possibility to assess gray balance, these usually work to determine full-tone ink densities and dot gain. The first objective of this study has been to evaluate the subjective quality experience (and objectively measurable factors) of print, where the quality control has been carried out based on gray balance control in sheet-fed offset. The second objective was to implement gray balance as a practical tool for the printers for a fast visual quality control in a sheet-fed offset printing. The study has shown that: 1) The gray balance can be used as a control parameter for control of quality in sheet fed offset. 2) A faster start-up and a more reliable print quality (fewer variations during production) can be achieved. The printer and the customer have access to a tool which facilitates communication, generates fewer misunderstandings, leads to less product returns and less production losses. With this tool it is easier for the printer to visually detect deviations without time consuming physical measurements. Also troubleshooting is easier; printers know instantly where the deviation is and can attend to it immediately.

Keyword
Gray balance, Quality, Sheet-fed offset, Strip
National Category
Media and Communication Technology
Identifiers
urn:nbn:se:kth:diva-12431 (URN)2-s2.0-78649657096 (Scopus ID)
Conference
60th Annual Technical Conference of the Technical Association of the Graphic Arts, TAGA - Disseminating Graphic Arts Research Internationally since 1948; San Francisco, CA; United States; 16 March 2008 through 19 March 2008
Note

QC 20100617

Available from: 2010-04-21 Created: 2010-04-21 Last updated: 2014-10-10Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
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  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
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  • Other locale
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Output format
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