Reflectance, illumination, and appearance in color constancy

We studied color constancy using a pair of identical 3-D Color Mondrian displays. We viewed one 3-D Mondrian in nearly uniform illumination, and the other in directional, nonuniform illumination. We used the three dimensional structures to modulate the light falling on the painted surfaces. The 3-D structures in the displays were a matching set of wooden blocks. Across Mondrian displays, each corresponding facet had the same paint on its surface. We used only 6 chromatic, and 5 achromatic paints applied to 104 block facets. The 3-D blocks add shadows and multiple reflections not found in flat Mondrians. Both 3-D Mondrians were viewed simultaneously, side-by-side. We used two techniques to measure correlation of appearance with surface reflectance. First, observers made magnitude estimates of changes in the appearances of identical reflectances. Second, an author painted a watercolor of the 3-D Mondrians. The watercolor's reflectances quantified the changes in appearances. While constancy generalizations about illumination and reflectance hold for flat Mondrians, they do not for 3-D Mondrians. A constant paint does not exhibit perfect color constancy, but rather shows significant shifts in lightness, hue and chroma in response to the structure in the nonuniform illumination. Color appearance depends on the spatial information in both the illumination and the reflectances of objects. The spatial information of the quanta catch from the array of retinal receptors generates sensations that have variable correlation with surface reflectance. Models of appearance in humans need to calculate the departures from perfect constancy measured here. This article provides a dataset of measurements of color appearances for computational models of sensation. © 2014 McCann, Parraman and Rizzi

Colour coded

This 300 word publication to be published by the Society of Dyers and Colourists (SDC) is a collection of the best papers from a 4-year European project that has considered colour from the perspective of both the arts and sciences.The notion of art and science and the crossovers between the two resulted in application and funding for cross disciplinary research to host a series of training events between 2006 and 2010 Marie Curie Conferences & Training Courses (SCF) Call Identifier: FP6-Mobility-4, Euros 532,363.80 CREATE – Colour Research for European Advanced Technology Employment. The research crossovers between the fields of art, science and technology was also a subject that was initiated through Bristol’s Festival if Ideas events in May 2009. The author coordinated and chaired an event during which the C.P Snow lecture “On Two Cultures’ (1959) was re-presented by Actor Simon Cook and then a lecture made by Raymond Tallis on the notion of the Polymath. The CREATE project has a worldwide impact for researchers, academics and scientists. Between January and October 2009, the site has received 221, 414 visits. The most popular route into the site is via the welcome page. The main groups of visitors originate in the UK (including Northern Ireland), Italy, France, Finland, Norway, Hungary, USA, Finland and Spain. A basic percentage breakdown of the traffic over ten months indicates: USA -15%; UK - 16%; Italy - 13%; France -12%; Hungary - 10%; Spain - 6%; Finland - 9%; Norway - 5%. The remaining approximate 14% of visitors are from other countries including Belgium, The Netherlands and Germany (approx 3%). A discussion group has been initiated by the author as part of the CREATE project to facilitate an ongoing dialogue between artists and scientists. http://createcolour.ning.com/group/artandscience www.create.uwe.ac.uk.Related papers to this research: A report on the CREATE Italian event: Colour in cultural heritage.C. Parraman, A. Rizzi, ‘Developing the CREATE network in Europe’, in Colour in Art, Design and Nature, Edinburgh, 24 October 2008.C. Parraman, “Mixing and describing colour”. CREATE (Training event 1), France, 2008

New technologies, same look - Crafting high dynamic range photographs to create a classical oil painting look

HDR photography allows artists to capture the full range of tonal values in high contrast real world scenes allowing for better latitude and creative control during post-production. With specialist HDR cameras being too expensive for the consumer market, the alternative method of photographing HDR images is by blending multiple varied exposures of the scene. The resulting images have characteristics in common with classical oil paintings in terms of the scene dynamic range depicted, as well as the softening effect inherent in the production process. HDR production and tonemapping processes can also amplify camera sensor and lens artifacts that bring unwanted attention to the fact that one is looking at a photographed image and not a painting. The images presented here were produced over the course of the author’s visual practice-research PhD journey exploring how HDR images can be crafted to create a painterly look reminiscent of classical landscape oil paintings whilst keeping unwanted camera, lens and software artifacts to a minimum, thus illustrating the extent to which digital technologies can be used to replicate pre-digital visual practices. The workflow, techniques and approaches are grounded in the photography and film visual effects disciplines

Enhancement and stylization of photographs

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 89-95).A photograph captured by a digital camera may be the final product for many casual photographers. However, for professional photographers, this photograph is only the beginning: experts often spend hours on enhancing and stylizing their photographs. These enhancements range from basic exposure and contrast adjustments to dramatic alterations. It is these enhancements - along with composition and timing - that distinguish the work of professionals and casual photographers. The goal of this thesis is to narrow the gap between casual and professional photographers. We aim to empower casual users with methods for making their photographs look better. Professional photographers could also benefit from our findings: our enhancement methods produce a better starting point for professional processing. We propose and evaluate three different methods for image enhancement and stylization. First method is based on photographic intuition and is fully automatic. The second method relies on expert's input for training; after the training this method can be used to automatically predict expert adjustments for previously unseen photographs. The third method uses a grammar-based representation to sample the space of image filter and relies on user input to select novel and interesting filters.by Vladimir Leonid Bychkovsky.Ph.D

Documenting bloodstain patterns concealed beneath architectural paint layers using multi-spectral forensic photography techniques

xvii, 678 leaves : ill. (chiefly col.) ; 29 cmIncludes abstract and appendices.Includes bibliographical references (leaves 174-185).The development of forensic photography techniques can aid agencies in the documentation of information regarding crime scene cleanup. This study compared reflective infrared, reflective ultraviolet, and fluorescence photography in the documentation of bloodstain patterns that had been concealed beneath layers of architectural paint. High Dynamic Range (HDR) photography, as well as a chemical analysis of all four paint types using Raman, Fibre Optic Reflectance, and Attenuated Total Internal Reflectance-Fourier Transform Infrared Spectroscopy was performed. The photography results for reflective infrared were negative; reflective ultraviolet for two of the four paint types were positive. Fluorescence photography had the most definitive visual information for the two white paints but were concluded negative for black and maroon. HDR was concluded to be negative for reflective infrared and reflective ultraviolet; however, results for fluorescence were positive. Finally, spectroscopy results supported visual information as well as providing spectral data relevant for understanding specific chemical observations

Gaming and Photography: Investigating the Elision of Illusion and the Actual

The application of aesthetics and techniques from photography into computer generated images leads audiences to read images of a virtual space similarly to images of a physical space. This phenomenon has allowed for a continuation in the cultural fascination with photorealism, and cases of audiences mistaking images from the virtual space as ‘real’. This thesis looks in detail at how the boundaries between the virtual and physical space shift when approaching the virtual space of a video game from the perspective of a photographer, rather than a player. It looks in detail at how audiences interpret images of the virtual space of video games when displayed in a form reminiscent of art photography. Photographs of the virtual and physical spaces were produced for online surveys and an exhibition to test audience perceptions of image origin. Participants were also asked to try and distinguish photorealism in the landscape form, urban form, and material form. Technical analysis of audience responses, combined with textual analysis of the images themselves, helped in determining the types of content, as well as styles of photography that were used by the audience as indexes to reality in the virtual space. In some cases, the technical theory could explain the thought process of the participants, however in other cases there were dominant factors that more significantly impacted participant interpretations, despite what theory suggested. This highlighted the blur that is emerging between the physical and virtual spaces. There were difficulties in designing tests that could identify and isolate the elements that influenced perceptions of photorealism, due to the complex, and sometimes unexpected, ways in which people made judgments about the images. A variety of factors and areas for future research arose from the tests, including using the medium of photography to document the ever-changing landscape of the virtual space

Stereoscopic high dynamic range imaging

Two modern technologies show promise to dramatically increase immersion in virtual environments. Stereoscopic imaging captures two images representing the views of both eyes and allows for better depth perception. High dynamic range (HDR) imaging accurately represents real world lighting as opposed to traditional low dynamic range (LDR) imaging. HDR provides a better contrast and more natural looking scenes. The combination of the two technologies in order to gain advantages of both has been, until now, mostly unexplored due to the current limitations in the imaging pipeline. This thesis reviews both fields, proposes stereoscopic high dynamic range (SHDR) imaging pipeline outlining the challenges that need to be resolved to enable SHDR and focuses on capture and compression aspects of that pipeline. The problems of capturing SHDR images that would potentially require two HDR cameras and introduce ghosting, are mitigated by capturing an HDR and LDR pair and using it to generate SHDR images. A detailed user study compared four different methods of generating SHDR images. Results demonstrated that one of the methods may produce images perceptually indistinguishable from the ground truth. Insights obtained while developing static image operators guided the design of SHDR video techniques. Three methods for generating SHDR video from an HDR-LDR video pair are proposed and compared to the ground truth SHDR videos. Results showed little overall error and identified a method with the least error. Once captured, SHDR content needs to be efficiently compressed. Five SHDR compression methods that are backward compatible are presented. The proposed methods can encode SHDR content to little more than that of a traditional single LDR image (18% larger for one method) and the backward compatibility property encourages early adoption of the format. The work presented in this thesis has introduced and advanced capture and compression methods for the adoption of SHDR imaging. In general, this research paves the way for a novel field of SHDR imaging which should lead to improved and more realistic representation of captured scenes

Advanced methods for relightable scene representations in image space

The realistic reproduction of visual appearance of real-world objects requires accurate computer graphics models that describe the optical interaction of a scene with its surroundings. Data-driven approaches that model the scene globally as a reflectance field function in eight parameters deliver high quality and work for most material combinations, but are costly to acquire and store. Image-space relighting, which constrains the application to create photos with a virtual, fix camera in freely chosen illumination, requires only a 4D data structure to provide full fidelity. This thesis contributes to image-space relighting on four accounts: (1) We investigate the acquisition of 4D reflectance fields in the context of sampling and propose a practical setup for pre-filtering of reflectance data during recording, and apply it in an adaptive sampling scheme. (2) We introduce a feature-driven image synthesis algorithm for the interpolation of coarsely sampled reflectance data in software to achieve highly realistic images. (3) We propose an implicit reflectance data representation, which uses a Bayesian approach to relight complex scenes from the example of much simpler reference objects. (4) Finally, we construct novel, passive devices out of optical components that render reflectance field data in real-time, shaping the incident illumination into the desired imageDie realistische Wiedergabe der visuellen Erscheinung einer realen Szene setzt genaue Modelle aus der Computergraphik für die Interaktion der Szene mit ihrer Umgebung voraus. Globale Ansätze, die das Verhalten der Szene insgesamt als Reflektanzfeldfunktion in acht Parametern modellieren, liefern hohe Qualität für viele Materialtypen, sind aber teuer aufzuzeichnen und zu speichern. Verfahren zur Neubeleuchtung im Bildraum schränken die Anwendbarkeit auf fest gewählte Kameras ein, ermöglichen aber die freie Wahl der Beleuchtung, und erfordern dadurch lediglich eine 4D - Datenstruktur für volle Wiedergabetreue. Diese Arbeit enthält vier Beiträge zu diesem Thema: (1) wir untersuchen die Aufzeichnung von 4D Reflektanzfeldern im Kontext der Abtasttheorie und schlagen einen praktischen Aufbau vor, der Reflektanzdaten bereits während der Messung vorfiltert. Wir verwenden ihn in einem adaptiven Abtastschema. (2) Wir führen einen merkmalgesteuerten Bildsynthesealgorithmus für die Interpolation von grob abgetasteten Reflektanzdaten ein. (3) Wir schlagen eine implizite Beschreibung von Reflektanzdaten vor, die mit einem Bayesschen Ansatz komplexe Szenen anhand des Beispiels eines viel einfacheren Referenzobjektes neu beleuchtet. (4) Unter der Verwendung optischer Komponenten schaffen wir passive Aufbauten zur Darstellung von Reflektanzfeldern in Echtzeit, indem wir einfallende Beleuchtung direkt in das gewünschte Bild umwandeln