Tableaux vivants. Da Diderot a Jeff Wall

What better way to begin a discussion of the Catholic sacramental imagination than with a nod to images? The art historian and cultural theorist W.J.T. Mitchell has famously and provocatively asked, “What do pictures want?” (Mitchell 1996, 2005). One answer, it turns out, is that they want “not to be interpreted, decoded, worshiped, smashed, exposed, or demystified by their beholders, or to enthrall their beholders” (Mitchell 2005, 48). In other words, they do not want to be reduced to texts and analyzed like them. Mitchell concedes that semiotic, hermeneutic, and rhetorical methods provide some help in disclosing the meaning of images. But, he asks, is the “meaning” the most fundamental thing that matters when we encounter a picture? We create a problem when we merely use some literary or political hermeneutic to “decode” images and thereby discover the desires of their producers and consumers, the intentions that lurk in the background and foreground of these pictures. By treating pictures as signs and symbols that need decoding, we end up ignoring the images themselves and focus more on those behind-the-scenes intentions that

Active illumination systems use a controllable light source and a light sensor to measure properties of a scene. For such a system to work reliably across a wide range of environments it must be able to handle the effects of global light transport, bright ambient light, interference from other active illumination devices, defocus, and scene motion. The goal of this thesis is to develop computational techniques and hardware arrangements to make active illumination devices based on commodity-grade components that work under real world conditions. We aim to combine the robustness of a scanning laser rangefinder with the speed, measurement density, compactness, and economy of a consumer depth camera. Towards this end, we have made four contributions. The first is a computational technique for compensating for the effects of motion while separating the direct and global components of illumination. The second is a method that combines triangulation and depth from illumination defocus cues to increase the working range of a projector-camera system. The third is a new active illumination device that can efficiently image the epipolar component of light transport between a source and sensor. The device can measure depth using active stereo or structured light and is robust to many global light transport effects. Most importantly, it works outdoors in bright sunlight despite using a low power source. Finally, we extend the proposed epipolar-only imaging technique to time-of-flight sensing and build a low-power sensor that is robust to sunlight, global illumination, multi-device interference, and camera shake. We believe that the algorithms and sensors proposed and developed in this thesis could find applications in a diverse set of fields including mobile robotics, medical imaging, gesture recognition, and agriculture.

Photonic crystals are periodic dielectric structures, where the periodicity varies on the wavelength scale. Analogous to electrons in semiconductors, the photon propagation can be described using a band structure in which transmission bands are separated by bandgaps, energy ranges at which light cannot exist inside the photonic crystals. This analogy suggests that photonic crystals may be suitable to fabricate the components needed for integrated optics. As yet most of the research done on photonic crystals has been focussed on using these bandgaps. However, many novel properties of light propagating in the transmission bands may also serve this purpose. This thesis studies theoretically and experimentally the light propagation in two dimensional planar photonic crystals with the aim of creating new components for integrated optics. A theoretical model based on Fourier analysis of electromagnetic Bloch waves was developed to describe light propagation in photonic crystals. This model gives an intuitive understanding of the novel phenomena observed in the transmission bands of the photonic crystal: negative refraction, auto-collimation and super-dispersion. This new approach clarifies the fundamental physics of these phenomena enabling their advantages and disadvantages to be easily evaluated for new optical functions; particular attention is paid to auto-collimation. The influence of the structural properties of the photonic crystal (lattice type, filling factor, etc.) is also studied and has been used to create two integrated optic components: a light condenser and a wavelength demultiplexer. The theoretical predictions have been tested experimentally on two dimensional planar photonic crystals fabricated in heterostructure GaAs/AlxGa1-xAs. The fabrication of these photonic crystals was the first experimental work undertaken in this thesis. Advanced microfabrication techniques enabled the fabrication of planar photonic close to those of the state-of-the-art. The optical properties of the fabricated photonic crystals fabricated were studied using the internal light source technique. This method uses photoluminescence generated by quantum wells or quantum dots as an internal light source to probe the optical properties of the photonic crystals. Initially the experimental setup was designed to study the bandgaps. However after some modifications the transmission bands could also be investigated. Another experimental improvement made was the introduction of a technique using coupled waveguides which reduces the losses by a factor of 10 and allowed the light in the photonic crystals to be studied over long distances. Adding a spatially resolved vertical detection, enabled the analysis of the light diffracted out of the plane in order to measure the propagation losses and to map the electromagnetic field. These two modifications were used to study components for integrated optics based on photonic crystals: waveguides and auto-collimators.

We have developed a new derivative-free algorithm based on Radial Basis Functions (RBFs). Derivative-free optimization is an active field of research and several algorithms have been proposed recently. Problems of this nature in the industrial setting are quite frequent. The reason is that in a number of applications the optimization process contains simulation packages which are treated as black boxes. The development of our own algorithm was originally motivated by an application in biomedical imaging: the medical image registration problem. The particular characteristics of this problem have incited us to develop a new optimization algorithm based on trust-region methods. However it has been designed to be generic and to be applied to a wide range of problems. The main originality of our approach is the use of RBFs to build the models. In particular we have adapted the existing theory based on quadratic models to our own models and developed new procedures especially designed for models based on RBFs. We have tested our algorithm called BOOSTERS against state-of-the-art methods (UOBYQA, NEWUOA, DFO). On the medical image registration problem, BOOSTERS appears to be the method of choice. The tests on problems from the CUTEr collection show that BOOSTERS is comparable to, but not better than other methods on small problems (size 2-20). It is performing very well for medium size problems (20-80). Moreover, it is able to solve problems of dimension 200, which is considered very large in derivative-free optimization. We have also developed a new class of algorithms combining the robustness of derivative-free algorithms with the faster rate of convergence characterizing Newtonlike-methods. In fact, they define a new class of algorithms lying between derivative-free optimization and quasi-Newton methods. These algorithms are built on the skeleton of our derivative-free algorithm but they can incorporate the gradient when it is available. They can be interpreted as a way of doping derivative-free algorithms with derivatives. If the derivatives are available at each iteration, then our method can be seen as an alternative to quasi-Newton methods. At the opposite, if the derivatives are never evaluated, then the algorithm is totally similar to BOOSTERS. It is a very interesting alternative to existing methods for problems whose objective function is expensive to evaluate and when the derivatives are not available. In this situation, the gradient can be approximated by finite differences and its costs corresponds to n additional function evaluations assuming that Rn is the domain of definition of the objective function. We have compared our method with CFSQP and BTRA, two gradient-based algorithms, and the results show that our doped method performs best. We have also a theoretical analysis of the medical image registration problem based on maximization of mutual information. Most of the current research in this field is concentrated on registration based on nonlinear image transformation. However, little attention has been paid to the theoretical properties of the optimization problem. In our analysis, we focus on the continuity and the differentiability of the objective function. We show in particular that performing a registration without extension of the reference image may lead to discontinuities in the objective function. But we demonstrate that, under some mild assumptions, the function is differentiable almost everywhere. Our analysis is important from an optimization point of view and conditions the choice of a solver. The usual practice is to use generic optimization packages without worrying about the differentiability of the objective function. But the use of gradient-based methods when the objective function is not differentiable may result in poor performance or even in absence of convergence. One of our objectives with this analysis is also that practitioners become aware of these problems and to propose them new algorithms having a potential interest for their applications.

Since the 1970s, feminist and LGBT scholarship has extensively focused on the impact that advertising, television and film have on the standardization and objectification of the female and lesbian body. However, little attention has been given to the images produced in global(izing) communication industries such as branding and stock photography. Brands and stock photographs alike may seem to be more invisible, although and perhaps because they are in fact much more pervasive than “traditional” media images. These images originate from major centers of post-industrial capitalist power and are used and consumed by multiple actors, ranging from communication professionals to ordinary consumers. In this article, I offer an in-depth critical reading of some key communication resources of two global corporations: the global coffeehouse chain Starbucks and the world-leading provider of stock photography Getty Images. First, I examine some of the key branding strategies used by Starbucks, with a specific focus on the deployment of the female body in the mermaid logo. Second, I examine Getty photographs aimed at representing lesbian subjectivities for a variety of uses. The differences that set us apart, or the eccentricities of our bodies, are increasingly exploited in globalizing contexts that require differentiation and distinction, though within the rigid structures that underlie the economic, political and cultural marketplaces of contemporaneity. For this reason, in my analysis I also and foremost focus on the visual treatment of key “abject” or “queer” features that characterize images produced both by Starbucks and Getty. In this way, I ultimately highlight some of the dynamics that underlie the coding of differences, rather than the homogenization of discursive practices in contemporary communication. Keywords: lesbian, female body, queer, abjection, stylization, Starbucks, Getty, branding, stock photography, visual communication, globalization.

This practice related research study explores my cognitive response to a biographical snapshot photograph celebrating my first day at school. The experience triggered an exploration of the relationship between snapshot photographs and memory. The finding of a second almost identical snapshot photograph of my son taken twenty years later by me prompted me to question why my father and I should take almost identical snapshots. I argue that the invention of photography was driven by the desire to capture the images created by the camera obscura by mark-making with the pencil of light as an aid memoir. I argue that the desire to externalise memory using mnemonic technology is innate with primal origins in parietal art and lithic technologies. The discourse explores the cultural evolution of technology through Jaques Derrida’s theory of originary technicity and Bernard Stiegler’s concept of the cultural evolution of technology by epiphylogenesis and the notion of the externalisation of memory as prosthesis. I explore the emergence of snapshot photography from the canon of photography through the theories of cultural evolution, technological momentum, and social constructivism, together with psycho-social notions of desire, ritual, performativity and intentionality in the establishment of snapshot photography as a ubiquitous ingrained social practice. The research is informed by a studio practice element that uses the adventures of Lewis Carroll’s, Alice as a conceptual framework to explore a journey of agency, self and auto didactical knowledge acquisition. I discuss the search for an appropriate methodological framework for art practice based research. My practice is a catalyst for enquiry; a project usually starts with an artefact that forms the locus of a question, the search for the answer to those questions, often leading epistemically, to unexpected places and relationships. The mode and manner of my enquiry are rhizomatous, pragmatic and serendipitous; the relationship between practice and theory is flexible, one informing the other. Through practice, I explore the deconstruction and textualisation of the visual metaphor of memory through the rhetorical devices of ekphrasis and memory texts and a visualisation of the nature and originary technicity of snapshot photography and an exploration of self and place. The thesis for this study is founded on the premise that snapshot photography is a socially constructed, phatic, mnemonic mark-making technology with origins in parietal forms of visual expression.

Computer vision and pattern recognition systems play an important role in our lives by means of automated face detection, face and gesture recognition, and estimation of gender and age. We have developed a gender classifier with performance superior to existing gender classifiers. This paper addresses the problem of gender classification using frontal facial images. The testbed consists of 500 images (250 females and 250 males) randomly withdrawn from the FERET facial database. Independent component analysis (ICA) is used to represent each image as a feature vector in a low dimensional subspace. Different classifiers are studied in this lower dimensional subspace. Our experimental results show the best accuracy of 96% in gender classification by combining ICA and support vector machines (SVMs).

Co-creative portraits open space to explore the interaction of photographic subjects and photographers as they collaborate to create intentional images. This still photographic method explores how the space of photographic creation and the resulting photographs not only respond to, but also engage and reflect the immediate inter-subjective, and broader, regional politics. Particularly, I examine this method, and the photographs it produces, in the context of the eastern Democratic Republic of the Congo - one of the densest spaces of humanitarian aid in the world. In North Kivu province, photography is produced daily for the purposes of fundraising, advocacy, and accountability. Aid agencies rely on the notion of photographs and their ability to ‘witness’ through portrayals of ‘documentary reality’. However, the visual imagescape of the eastern DRC is not bound by humanitarian imagery alone. In fact it is home to a thriving local photographic enterprise. Through co-creative portraits I examine the overlapping fields of ‘daily vernacular’ and ‘humanitarian photography,’ focusing on how individuals tack back and forth across these types of representation in front of the camera, particularly in response to dialectic social factors including space, time, and in their anticipations of their photographer. Therein, this article makes a two-pronged argument: 1) I argue that co-creative portraits contribute to the production of experiential, anthropological knowledge through photography. 2) With attention to the explanations, movements, and negotiations that produce the photographs, I argue that this method shows the constructed, subjective nature of photography, even in spaces of humanitarian aid.

The aim of the cognitive-developmental study has been to determine features of the image of God and indications of the relationship with God formed by adolescents. The definition of the image of God adopted in this paper has three aspects: (1) knowledge about God, (2) emotional experiences of God, and (3) behavioral tendencies towards God. It should be noted that the image of God is formed by imagination to a considerable degree, as we shape our mental representation of God on the basis of imagination. In the study, 114 adolescent Catholics were tested with the projection drawing “My God and I”. The position, shape, size, colors and the way of drawing the figure or symbol of God belong to the formal part of the analysis, while the meanings ascribed to the figure or symbol of God, i.e. the semantics of the representation, constitute the aspect of content. The results of the study have helped to isolate the dimensions of form and content in the image of God and to present their different categorizations.

Objective To investigate the characteristics and mechanisms of attentional bias in anxiety sensitivity individuals. Methods By using Anxiety Sensitivity Index (ASI), 23 participants were included in the high score group and 20 participants were included in the low score group.Then, 2 (between-subject factor: the high and low score group) ×2 (within-subject factor: the positive and negative picture) mixed design experiments were adopted.Emotional faces picture pairs were chosen as stimuli.Picture pairs were presented 100 ms in experiment 1 and 1 250 ms in experiment 2.Dot-probe task was adopted to inspect the attentional bias and the response time and correct rate were recorded. Results Experiment 1 implied the main effect of type of pictures was found in mixed design experiments(F(1, 41)=4.40, P 0.05). And positive score showed the attentional bias to some certain extent.Significant outcome was found by negative score between two groups (F(1, 41)=6.41, P<0.05). It implied that the high score group tended to avoid the negative pictures and the low score group had the tendency of input effect. Conclusion At the initial stage of attention, anxiety sensitivity individuals had the attentional bias to negative emotional faces and avoidance in the late stage of attention.It suggests that the attentional bias of anxiety sensitivity individuals may have an important effect on the development of the mental disorders. Key words: Anxiety sensitivity; Attentional bias; Dot-probe task

According to Gaston Bachelard, home, both as a physical and mental shelter for human beings, involves a real space around which the imagination creates further images of warmth and coziness. The theme of displacement from home is pre-eminent in ”King Lear”, and thus the tragedy serves as a striking example of Bachelard's poetics of space. In ”King Lear”, although castles appear to be shelters for people, Lear can neither possess nor have access to them after he divides his kingdom and bestows all his property on his two elder daughters, who then banish him and keep him away from both them and their castles. Lear's roaming in the storm ends with his being forced to take refuge in a hovel. Before he reluctantly enters the hovel, contrasting ideas of a comfortable house and of a miserable hut become twisted in Lear's mind and speech. As he realizes the wretchedness of life in a hovel, Lear's previous picture of home as an intimate space is challenged and demolished. A cozy home becomes an unattainable place for Lear, and brings forth ever more destructive thoughts. However, whereas to him castles are now fraught with treachery and disaster, the hovel provides Lear with an epiphanic locus where he reaches certain profound realizations. In the hovel, Lear meets and befriends Edgar, disguised as Mad Tom. Leaving the hovel, Lear roams on the heath, which extends his imagination and contemplation. The values of these loci are challenged and remodeled in the play: the supposed sanctuary for Lear now becomes the space of darkness. Because of radical changes in his physical locales, Lear's mental spaces are disrupted. As with the poetics of space, the play becomes a fruitless journey in which Lear looks for a home, with the possibility that he may just find this before the end.

(Semi)immersive displays like back projection walls have become widely used in various visual domains. Despite the superior image quality of `through-the-windows VR' users are still not satisfied with the interaction capabilities - mostly due to the extra wiring for the interaction devices. This paper represents a hand gesture interaction system for a back-projection wall environment, supporting object manipulation (translation, rotation, and uniform scale) and selection tasks through the vision-tracking technique. We propose to use thimble-shaped fingertip markers made of white printing paper with a `black light' source. Gesture parameters are calculated by 3D positions of the marked fingertips and their pinching states

An understanding of light and its interaction with matter is essential to produce images. As the modeling of light sources, light transport and light reflection improves, it becomes possible to render images with increasing realism. The central motivation behind this thesis is to improve realism in computer graphics images by more accurate local shading models and to assist the user to obtain the desired lighting effects with these more complex models. The first part of the thesis addresses the problem of rendering surfaces illuminated by extended (linear and area) light sources. To compute the light reflected by a surface element in a given direction, one needs to determine the unoccluded regions (shadowing) of each light source and then to compute the light reflection (shading) from each of these regions. Traditionally, point light sources are distributed on the lights to approximate both the shadowing and the shading. Instead, an efficient analytical solution is developed for the shading. Shadowing from extended light sources is a fairly expensive process. To give some insights on the complexity of computing shadows, some properties of shadows and algorithms are presented. To reduce the cost of computing shadows from linear light sources, two acceleration schemes, extended from ray tracing, are introduced and evaluated. The second part of this thesis addresses the problem of achieving a desired shading effect by building up systems of constraints. This approach is called inverse shading. It allows a user to obtain a desired lighting effect by interacting directly with the scene model. An interactive modeling system has been built to study the introduction of rendering issues into the modeling process itself. Two rendering aspects are considered: shading and shadows. By specifying a highlight position and size, the unique direction of a directional light source as well as the surface glossiness are determined. Interactively moving this highlight on the surface redefines the light direction while changing its size redefines the surface glossiness. By manipulating shadow volumes (the volume within which a particular light cannot be completely seen), the light source definition and position can be modified. By assigning colours to various points in a 3D scene, information about the colour of a surface as well as other surface characteristics can be deduced. This relatively new concept of defining the causes by manipulating the effects is expected to have a major impact on the design of future computer graphics modeling systems. It begins a new family of tools for the design of more intuitive user interfaces.

Computer-based Multiple External Representations (MERs) have been found in some cases to help and in others to hinder the learning process. This thesis examines how varying the external representations that are presented in a computer environment influences the strategies that learners choose when tackling mathematics tasks. It has been noted (Ainsworth, 2006) that learners fail to transfer insights from one representation to another. Previous work analysing video data of learners' problem-solving with computer-based MERs emphasises the need to identify which representation is being considered by a learner as utterances are made, and to examine more closely learners' movement between representations. This research focuses on the relationship between strategy and representation during learners' problem solving. A set of analytical techniques was developed to characterise learner strategies, to identify how different computer-based MERs influence strategy choices, and to explore how these choices change over the course of task completion. Rich data were collected using a variety of technologies: learners' shifts in attention were recorded using an unobtrusive eye-tracking device and screen capture software; keyboard and mouse actions were logged automatically; utterances and gestures were video recorded; notes and sketches were recorded in real-time using a Tablet PC. This research suggests how integrated analysis of learners' gazes, actions, writing, sketches and utterances can better illuminate subtle cognitive strategies. The study involved completion of three tasks by eighteen participants using multiple mathematical representations (numbers, graphs and algebra) presented in different computer-based 'instantiations': Static (non-moving, non-changing, non-Interactive); Dynamic (capable of animation following keyboard inputs); Interactive (directly manipulable using a mouse). Having computer-based MERs available to learners provides an opportunity to use representations with which they are comfortable. A detailed analysis showed that both representation and instantiation have an impact on strategy choice. It identified differences in expression of inferences, construction of visual images, and attention to representations between different types of instantiation. One of the important findings of the research is that learners are less likely to use imagining strategies when representational instantiation is Interactive. These results may provide some explanation of how interactivity helps or hinders learners' understanding of multiple representations.

This paper presents a refl ection on the critical role and the politics behind the photographic look at the context the visual culture in Latin American. We present the photographic look as an agent of social action in the context of visual culture. The photographic documentation, as one of the main artifacts of visual culture, has the power to provide an overview, through a non-verbal communication, between the registered fact, the cut-off of the Real, and the interpretations drawn on it, creating thereby art and realism. This relation of correspondence between representation and interpretation has always been subject to the established cultural conventions, but it represents a social action of the look into a possible visual awareness. We argue that social action of the look sharpens its own centrality in the dimensions of the public sphere, in which the change of this form of representation is one way to increase the autonomy of the image in the public space, and to notice it each time more decontextualized in relation to its referent.