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Printing Beyond Color: Spectral and Specular Reproduction

Samadzadegan, Sepideh (2016)
Printing Beyond Color: Spectral and Specular Reproduction.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung

Kurzbeschreibung (Abstract)

For accurate printing (reproduction), two important appearance attributes to consider are color and gloss. These attributes are related to two topics focused on in this dissertation: spectral reproduction and specular (gloss) printing. In the conventional printing workflow known as the metameric printing workflow, which we use mostly nowadays, high-quality prints -- in terms of colorimetric accuracy -- can be achieved only under a predefined illuminant (i.e. an illuminant that the printing pipeline is adjusted to; e.g. daylight). While this printing workflow is useful and sufficient for many everyday purposes, in some special cases, such as artwork (e.g. painting) reproduction, security printing, accurate industrial color communication and so on, in which accurate reproduction of an original image under a variety of illumination conditions (e.g. daylight, tungsten light, museum light, etc.) is required, metameric reproduction may produce satisfactory results only with luck. Therefore, in these cases, another printing workflow, known as spectral printing pipeline must be used, with the ideal aim of illuminant-invariant match between the original image and the reproduction. In this workflow, the reproduction of spectral raw data (i.e. reflectances in the visible wavelength range), rather than reproduction of colorimetric values (colors) alone (under a predefined illuminant) is taken into account. Due to the limitations of printing systems extant, the reproduction of all reflectances is not possible even with multi-channel (multi-colorant) printers. Therefore, practical strategies are required in order to map non-reproducible reflectances into reproducible spectra and to choose appropriate combinations of printer colorants for the reproduction of the mapped reflectances. For this purpose, an approach called Spatio-Spectral Gamut Mapping and Separation, SSGMS, was proposed, which results in almost artifact-free spectral reproduction under a set of various illuminants. The quality control stage is usually the last stage in any printing pipeline. Nowadays, the quality of the printout is usually controlled only in terms of colorimetric accuracy and common printing artifacts. However, some gloss-related artifacts, such as gloss-differential (inconsistent gloss appearance across an image, caused mostly by variations in deposited ink area coverage on different spots), are ignored, because no strategy to avoid them exists. In order to avoid such gloss-related artifacts and to control the glossiness of the printout locally, three printing strategies were proposed. In general, for perceptually accurate reproduction of color and gloss appearance attributes, understanding the relationship between measured values and perceived magnitudes of these attributes is essential. There has been much research into reproduction of colors within perceptually meaningful color spaces, but little research from the gloss perspective has been carried out. Most of these studies are based on simulated display-based images (mostly with neutral colors) and do not take real objects into account. In this dissertation, three psychophysical experiments were conducted in order to investigate the relationship between measured gloss values (objective quantities) and perceived gloss magnitudes (subjective quantities) using real colored samples printed by the aforementioned proposed printing strategies. These experiments revealed that the relationship mentioned can be explained by a Power function according to Stevens' Power Law, considering almost the entire gloss range. Another psychophysical experiment was also conducted in order to investigate the interrelation between perceived surface gloss and texture, using 2.5D samples printed in two different texture types and with various gloss levels and texture elevations. According to the results of this experiment, different macroscopic texture types and levels (in terms of texture elevation) were found to influence the perceived surface gloss level slightly. No noticeable influence of surface gloss on the perceived texture level was observed, indicating texture constancy regardless of the gloss level printed. The SSGMS approach proposed for the spectral reproduction, the three printing strategies presented for gloss printing, and the results of the psychophysical experiments conducted on gloss printing and appearance can be used to improve the overall print quality in terms of color and gloss reproduction.

Typ des Eintrags: Dissertation
Erschienen: 2016
Autor(en): Samadzadegan, Sepideh
Art des Eintrags: Erstveröffentlichung
Titel: Printing Beyond Color: Spectral and Specular Reproduction
Sprache: Englisch
Referenten: Fellner, Professor Dieter W. ; Dörsam, Professor Edgar ; Hardeberg, Professor Jon Yngve ; Buchmann, Professor Johannes A. ; Hamacher, Professor Kay ; Fischlin, Professor Marc
Publikationsjahr: 5 Februar 2016
Ort: Darmstadt
Datum der mündlichen Prüfung: 30 November 2015
URL / URN: http://tuprints.ulb.tu-darmstadt.de/5261
Kurzbeschreibung (Abstract):

For accurate printing (reproduction), two important appearance attributes to consider are color and gloss. These attributes are related to two topics focused on in this dissertation: spectral reproduction and specular (gloss) printing. In the conventional printing workflow known as the metameric printing workflow, which we use mostly nowadays, high-quality prints -- in terms of colorimetric accuracy -- can be achieved only under a predefined illuminant (i.e. an illuminant that the printing pipeline is adjusted to; e.g. daylight). While this printing workflow is useful and sufficient for many everyday purposes, in some special cases, such as artwork (e.g. painting) reproduction, security printing, accurate industrial color communication and so on, in which accurate reproduction of an original image under a variety of illumination conditions (e.g. daylight, tungsten light, museum light, etc.) is required, metameric reproduction may produce satisfactory results only with luck. Therefore, in these cases, another printing workflow, known as spectral printing pipeline must be used, with the ideal aim of illuminant-invariant match between the original image and the reproduction. In this workflow, the reproduction of spectral raw data (i.e. reflectances in the visible wavelength range), rather than reproduction of colorimetric values (colors) alone (under a predefined illuminant) is taken into account. Due to the limitations of printing systems extant, the reproduction of all reflectances is not possible even with multi-channel (multi-colorant) printers. Therefore, practical strategies are required in order to map non-reproducible reflectances into reproducible spectra and to choose appropriate combinations of printer colorants for the reproduction of the mapped reflectances. For this purpose, an approach called Spatio-Spectral Gamut Mapping and Separation, SSGMS, was proposed, which results in almost artifact-free spectral reproduction under a set of various illuminants. The quality control stage is usually the last stage in any printing pipeline. Nowadays, the quality of the printout is usually controlled only in terms of colorimetric accuracy and common printing artifacts. However, some gloss-related artifacts, such as gloss-differential (inconsistent gloss appearance across an image, caused mostly by variations in deposited ink area coverage on different spots), are ignored, because no strategy to avoid them exists. In order to avoid such gloss-related artifacts and to control the glossiness of the printout locally, three printing strategies were proposed. In general, for perceptually accurate reproduction of color and gloss appearance attributes, understanding the relationship between measured values and perceived magnitudes of these attributes is essential. There has been much research into reproduction of colors within perceptually meaningful color spaces, but little research from the gloss perspective has been carried out. Most of these studies are based on simulated display-based images (mostly with neutral colors) and do not take real objects into account. In this dissertation, three psychophysical experiments were conducted in order to investigate the relationship between measured gloss values (objective quantities) and perceived gloss magnitudes (subjective quantities) using real colored samples printed by the aforementioned proposed printing strategies. These experiments revealed that the relationship mentioned can be explained by a Power function according to Stevens' Power Law, considering almost the entire gloss range. Another psychophysical experiment was also conducted in order to investigate the interrelation between perceived surface gloss and texture, using 2.5D samples printed in two different texture types and with various gloss levels and texture elevations. According to the results of this experiment, different macroscopic texture types and levels (in terms of texture elevation) were found to influence the perceived surface gloss level slightly. No noticeable influence of surface gloss on the perceived texture level was observed, indicating texture constancy regardless of the gloss level printed. The SSGMS approach proposed for the spectral reproduction, the three printing strategies presented for gloss printing, and the results of the psychophysical experiments conducted on gloss printing and appearance can be used to improve the overall print quality in terms of color and gloss reproduction.
Alternatives oder übersetztes Abstract:
Alternatives AbstractSprache

Für eine akkurate drucktechnische Reproduktionen sind insbesondere zwei Eigenschaften von Bedeutung: Farbe und Glanz. Die Reproduktion dieser zwei Wahrnehmungsattribute sind die beiden Fokusthemen in dieser Dissertation: spektrale Reproduktion und Glanzdruck. Der heute in der Druckindustrie verwendete metamere Workflow passt die Reproduktion an das Original lediglich für eine vordefinierte Lichtart an. In den meisten Fällen ist eine solche Reproduktion ausreichend. Im Bereichen wie der Kunstreproduktion, dem Sicherheitsdruck, in der industriellen Farbkommunikation, muss die Reproduktion mit dem Original unter einer Vielzahl von Lichtarten übereinstimmen (z.B. Tageslicht, Glühlampenlicht oder einer speziellen LED Beleuchtung) -- eine Eigenschaft, die die metamere Reproduktion per Definition i.A. nicht leisten kann. Für diese Anwendungen müssen die Reflektionsspektren des Originals durcktechnisch Reproduziert werden. Wegen der Limitierungen existierender Drucksysteme, ist die Reproduktion gegebener Reflexionsspektren i.A. unmöglich. Daher müssen Strategien entwickelt werden, um nicht reproduzierbare in die Menge der reproduzierbaren Reflexionsspektren zu transformieren und um Druckeransteuerungswerte auszuwählen, die diese Reflektionsspektren artefaktfrei zu reproduzieren. In dieser Dissertation wurde hierfür ein Verfahren namens "Spatio-Spectral Gamut Mapping and Separation", SSGMS, vorgestellt, das nahezu artefaktfreie Ergebnisse liefert und die Reproduktion an das Original farbmetrisch für eine vorgegebene Menge an Lichtarten anpasst. Heutzutage werden nur die farbmetrische Genauigkeit und strukturelle Bildartefakte in der Qualitätskontrolle überprüft. Eigenschaften die sich auf Glanz beziehen, wie zum Beispiel "gloss-differential" (inkonsistente Verteilung des Glanzes über das Bild hinweg, meistens erzeugt durch unregelmäßige Flächendeckung der verwendeten Tinten), werden nicht geprüft, da keine Strategie existiert um diese Fehler zu vermeiden. Zur Vermeidung solcher Glanzartefakte, und um die Glanzeigenschaften lokal anzupassen, werden in dieser Dissertation drei drucktechnische Verfahren vorgestellt. Für eine perzeptuell akkurate Reproduktion von Farb- und Glanzeigenschaften, ist das Wissen über die Beziehung zwischen messtechnischen Werten und wahrgenommenen Größen Voraussetzung. Im Bereich der Farbe existieren bereits entsprechende Modelle sowie nahezu wahrnehmungsgleichabständige Farbräume, die für die Farbreproduktion erfolgreich eingesetzt werden. Solche Modelle fehlen jedoch für die drucktechnische Glanzreproduktion. Die meisten der existierenden Studien basieren auf Experimenten, die Glanz am Bildschirm simulieren (meistens mit unbunten Farben) und keine realen Objekte verwenden. In dieser Dissertation, wurden drei psychophysische Experimente durchgeführt, um die Beziehung zwischen gemessenen Glanz (objektiven Größen) und wahrgenommenen Glanz (subjektiven Größen) zu untersuchen. Hierfür wurden farbige reale Proben verwendet, die drucktechnisch mit den drei oben erwähnten Verfahren erstellt wurden. Das Ergebnis der Experimente zeigt, dass die Beziehung mit einer Potenzfunktion, gemäß des Stevensschen Potenzgesetzes, beschrieben werden kann. In einem weiteren Experiment wurde die Beziehung zwischen wahrgenommenen Oberflächenglanz und Höhentextur untersucht. Hierbei wurden, 2,5D Proben mit zwei verschiedenen Texturtypen und unterschiedlichen Glanz- und Texturhöhenstufen verwendet. Das Ergebnis dieses Experiments zeigt, dass verschiedene makroskopische Textur-Typen und Höhenstufen einen leichten Einfluss auf die Glanzempfindung haben. Ein Einfluss des Oberflächenglanzes auf die beobachtete Texturhöhe konnte nicht festgestellt werden, was darauf hindeutet, dass die Texturwahrnehmung nicht von der Stärke des Oberflächenglanzes beeinflusst wird. Das SSGMS Verfahren zur spektralen Reproduktion, die drei Druckstrategien für den Glanzdruck und die Ergebnisse der psychophysischen Experimente zur Untersuchung der Glanzwahrnehmung, können zur Verbesserung der Gesamtqualität der drucktechnischen Farb- und Glanzreproduktion benutzt werden.

Deutsch
URN: urn:nbn:de:tuda-tuprints-52615
Sachgruppe der Dewey Dezimalklassifikatin (DDC): 000 Allgemeines, Informatik, Informationswissenschaft > 004 Informatik
Fachbereich(e)/-gebiet(e): 20 Fachbereich Informatik
20 Fachbereich Informatik > Graphisch-Interaktive Systeme
Hinterlegungsdatum: 14 Feb 2016 20:55
Letzte Änderung: 14 Feb 2016 20:55
PPN:
Referenten: Fellner, Professor Dieter W. ; Dörsam, Professor Edgar ; Hardeberg, Professor Jon Yngve ; Buchmann, Professor Johannes A. ; Hamacher, Professor Kay ; Fischlin, Professor Marc
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: 30 November 2015
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