Simulated images can provide insight into the performance of optical systems, especially those with complicated features. Many modern solutions for presbyopia and cataracts feature sophisticated power geometries or diffractive elements. Some intraocular lenses (IOLs) arrive at multifocality through the use of a diffractive surface and multifocal contact lenses have a radially varying power profile. These type of elements induce simultaneous vision as well as affecting vision much differently than a monofocal ophthalmic appliance. With myriad multifocal ophthalmics available on the market it is difficult to compare or assess performance in ways that effect wearers of such appliances. Here we present software and algorithmic metrics that can be used to qualitatively and quantitatively compare ophthalmic element performance, with specific examples of bifocal intraocular lenses (IOLs) and multifocal contact lenses. We anticipate this study, methods, and results to serve as a starting point for more complex models of vision and visual acuity in a setting where modeling is advantageous. Generating simulated images of real- scene scenarios is useful for patients in assessing vision quality with a certain appliance. Visual acuity estimation can serve as an important tool for manufacturing and design of ophthalmic appliances.

Digital images are being created and uploaded online in large numbers and this can be attributed to three main interconnected factors: a change in attitudes towards photography and its role in society; technological advancements in the camera industry; and changes in web technology. Many of these digital images are being uploaded to Flickr, one of the most popular of the new web 2.0 image management and sharing applications. Flickr supports secure storage, sharing, online communities, and tagging. Tagging is intended to aid with the organisation, description, and retrieval of images, and as tagging in Flickr generally relates to personal images (e.g., photographs), the tags assigned are highly subjective. Previous research has investigated motivations to upload and tag images in web 2.0 image management and sharing applications, and types of tags used in web 2.0 image management and sharing applications, and a limited number of studies have attempted to correlate the two, however no research has attempted to correlate the two whilst also taking into account the subjective nature of image tagging. Identifying the discrepancies between why people want to use Flickr, and how they use it can help system designers and users to get the best out of these applications. This thesis compares users’ motivations to upload and tag their images in Flickr with how they tag their images in practice. The study used a quantitative survey methodology consisting of a semi-structured questionnaire to explore user motivations. Tagging practices were investigated via a manual tag classification scheme applied to automatically extracted Flickr tags. The questionnaire results show that Flickr users are primarily motivated to upload their images to Flickr for the purposes of social-communication (i.e., to draw attention to their images for comments and feedback and to express and present aspects of their personality and identity) and for socialorganisation (i.e., so other people can access and view the images uploaded). However, tagging images in Flickr is not associated with the motivation of social-organisation and is instead more closely aligned to social-communication, and self-organisation (i.e., as a way of organising images for personal search and retrieval). Self-communication (i.e., documenting and recording for memory and personal reflection) was not found to be a popular motivation for either uploading or tagging images. Flickr users that are motivated to upload their images for the purposes of self-organisation have the clearest tagging practice and they predominantly use tags that are only meaningful to themselves. Gender, pro account status, number of images, and number of contacts are also strong predictors of tagging practice. However, overall, tagging practice is more closely associated with image content than with the motivation the user has. Although the results show that socialcommunication is the most prominent factor in motivating users to upload their images and in motivating users to tag their images, the findings reveal that users who are motivated to upload their images for the purposes of social-organisation are not using the system to its full potential.

A practical model is proposed for predicting the detectability of targets at arbitrary locations in the visual field, in arbitrary gray-scale backgrounds, and under photopic viewing conditions. The major factors incorporated into the model include: (i) the optical point spread function of the eye, (ii) local luminance gain control (Weber's law), (iii) the sampling array of retinal ganglion cells, (iv) orientation and spatial-frequency dependent contrast masking, (iv) broadband contrast masking, (vi) and efficient response pooling. The model is tested against previously reported threshold measurements on uniform backgrounds (the ModelFest data set and data from Foley et al. 2007), and against new measurements reported here for several ModelFest targets presented on uniform, 1/f noise, and natural backgrounds, at retinal eccentricities ranging from 0 to 10 deg. Although the model has few free parameters, it is able to account quite well for all the threshold measurements. / text

Voir et entendre la destruction des Juifs d’Europe analyse l’aporie sur laquelle butent les documentaires à la télévision française et allemande, de 1960 à 2000. De Nuit et Brouillard du Français Alain Resnais aux séries de l’Allemand Guido Knopp, en passant par le Mein Kampf de Erwin Leiser, par Les Dossiers de l’écran consacrés à la diffusion d’Holocaust à la télévision française, par Shoah de Claude Lanzmann et d’autres films majeurs, tous s’affrontent à l’impossibilité de représenter, via l’image d’archives et le témoignage, de donner à « voir » et à « entendre » l’extermination de plus de cinq millions de personnes. L’examen minutieux de l’usage du témoignage et de l’image d’archives permet de dégager les stratégies mises en place, au fil du temps, par les réalisateurs pour contourner cette aporie. Les métamorphoses du statut et de la fonction des traces sonores et visuelles au sein du récit documentaire jettent également un éclairage sur la définition fluctuante de l’événement historique, sur les déplacements de regards et de sens portés sur le matériel iconographique et les souvenirs des acteurs de l’époque qui bousculent immanquablement la perception de l’histoire des Juifs sous le nazisme. Parallèlement à cette analyse interne, proposant un savoir non plus livresque du film, mais, au contraire un savoir qui intègre ses qualités propres, que sont l’audio et le visuel, la focale s’élargit au contexte mémoriel de la réalisation et de la diffusion du film afin d’évaluer le degré de singularité du discours élaboré par son auteur. Le documentaire est-il créateur de débats et d’événements, de sources de représentations et de croyances ? Donne-t-il, au contraire, au débat l’occasion de s’exprimer, limitant alors son rôle à un effet de miroir – fidèle ou non – des mémoires collectives ? Au regard de la connexité des sources (orales, visuelles et scripturales) entre l’historien et le réalisateur de documentaires, se superpose une interrogation relative à la nature du discours énoncé par le film : est-il d’ordre historique ou métahistorique ? Est-il du domaine de la connaissance ou, au contraire, s’inscrit-il dans la perspective d’un discours sur l’histoire utilisant les données historiques pour servir des enjeux du temps présent qui imposent ce dont il faut se souvenir ? Cette approche, replaçant les représentations documentaires dans leur propre contexte mémoriel et historiographique s’enrichit d’une perspective comparatiste entre les représentations documentaires allemandes et françaises qui a l’avantage de sortir des débats et enjeux nationaux relatifs au film documentaire. Voir et entendre la destruction des Juifs d’Europe présente ainsi une histoire culturelle et critique de la mémoire télévisuelle de l’événement juif de la Seconde guerre mondiale

A brief study of the imagery of the bilateral symmetric optical system is presented. This study has been developed with a theoretical structure similar to that of the rotationally symmetric optical system and can be considered a generalization. It provides a simple, clear understanding of the main features of the imagery of the optical systems under consideration. and gives useful design insight. Some design examples are provided that illustrate the use and value of the theory developed.

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