Color Vision

Illumination invariance remains the most researched, yet the most challenging aspect of automatic face recognition. In this paper we investigate the discriminative power of colour-based invariants in the presence of large illumination changes between training and test data, when appearance changes due to cast shadows and non-Lambertian effects are significant. Specifically, there are three main contributions: (i) we employ a more sophisticated photometric model of the camera and show how its parameters can be estimated, (ii) we derive several novel colour-based face invariants, and (iii) on a large database of video sequences we examine and evaluate the largest number of colour-based representations in the literature. Our results suggest that colour invariants do have a substantial discriminative power which may increase the robustness and accuracy of recognition from low resolution images.

1 Dep. Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, São Paulo, Brasil 2 Núcleo de Neurociências e Comportamento, Universidade de São Paulo, São Paulo, Brasil 3 Dep. Fisiologia Universidade Federal do Pará, Belém, Brasil 4 Núcleo de ...

Measurement of ocular wavefront aberration is becoming a popular clinical technique due to recent technical advances and an increasing awareness of its potential for practical application in the fields of surgical and optical refractive correction. In addition, information about the status of peripheral refraction determined from ocular wavefront aberrations is now being used to monitor the progression of myopia and other refractive errors in children, and as a basis for the study of the process of emmetropization. Several finite, anatomically accurate, wide-angled, model eyes have been proposed previously in an effort to produce a schematic eye that accurately reproduces vision under different practical circumstances. This paper compares these models in terms of their wavefront aberration, image quality metrics and peripheral refraction profiles and contrasts these with data from real eyes to assess their relative utility.

To determine whether implantation of the AcrySof Natural intraocular lens (IOL) worsened the severity of existing color deficit in congenital partial red–green color deficient individuals (CPRG).A prospective controlled randomized double-masked analysis of 30 consecutive patients with CPRG defect and bilateral cataracts received a Natural IOL (test group) in 1 eye and a single-piece AcrySof IOL (control group) in the other eye. Patients were tested unilaterally to detect CPRG defect using Ishihara pseudoisochromatic plates and the Farnsworth D-15 test. Plates 1 to 21 measured the Ishihara error score; plates 22 to 25 indicated severity of defect based on clarity of both numerals as partial mild/moderate (both visible), partial severe defect (only 1 visible). The D-15 test is based on number of diametrical crossings on the circular diagram; severity is graded as mild (1 crossing), moderate (2 crossings), or severe (>2 crossings). Tests were performed before and after IOL implantation at 1, 3, and 6 months. At mean follow-up of 6.13 months ± 1.2 (SD), analysis of variance test judged the difference in error scores and cross tabulation represented change in number of diametrical crossings.The mean age was 62.3 ± 8.5 years. All patients were men. Before IOL implantation, all patients had moderate CPRG defect on both tests. The Ishihara error score in the test and control groups did not reveal statistically significant differences (P = .505 and P = .119, respectively). With D-15, none of the patients in the test or control group showed >2 crossings.The implantation of AcrySof Natural IOL did not worsen the preexisting severity of color defect in CPRG individuals.

This paper was submitted to James S. McDonnell Foundation as a part of an application to for a James S. McDonnell Centennial Scholarship.  It addresses the question of what neuroscience can do for philosophy and vice versa using the example of human colour vision.

Recent research on human perception and its implications for the design of aircraft and ground-vehicle display systems is surveyed. Topics addressed include selective visual attention, command and status displays, foveal and peripheral displays, navigation displays, auditory displays, color and pictorial displays, head-up displays, automation, and dual-task performance and pilot workload. Diagrams, drawings, graphs, and photographs are provided.

Le dépistage de la qualité de la vision des enfants en âge d′être scolarisés (à partir de 5-6 ans) doit comprendre un examen de la vision des couleurs, les déficiences liées au chromosome X étant les plus fréquentes (8 % des garçonnets et 0,4 % des fillettes). Cet article présente les bases neurophysiologiques de ces déficiences, en relation avec les photopigments portés par les cônes et leurs classifications. Les principes des tests utilisés pour qualifier et quantifier ces déficiences sont rappelés et reliés aux bases de la physiologie visuelle, ce qui en facilite la compréhension. Une stratégie de dépistage est proposée à l′aide de trois tests cliniques faciles à utiliser par le médecin scolaire, généraliste ou pédiatre. Le test d′Ishihara est spécifique des dyschromatopsies liées à l′X. Si la lecture de ses planches est normale, la vision des couleurs est normale. En cas de doute ou si plusieurs planches sont anormalement perçues, les rangements des pions des Panel D 15 standard et désaturé doivent être réalisés successivement. Une stratégie est proposée qui aboutit à la qualification de ces déficiences en type protan ou deutan, qui sont les plus fréquentes, et à leur quantification : protanopie ou deutéranopie, protanomalie ou deutéranomalie extrême, modérée ou légère. Des exemples sont donnés montrant que, dans la majorité des cas, le dépistage est aisé et rapide. La reconnaissance précoce d′une déficience de la vision des couleurs est essentielle pour alerter parents ou éducateurs sur les limites de la perception colorée de l′enfant et adapter son apprentissage.Vision screening of school children at 5-6 years of age must include color vision screening. X-linked dyschromatopsia is the most frequent disorder affecting 8% of boys and 0.4% of girls. This paper presents the physiology of these deficiencies caused by an alteration of the spectral absorption properties of one of the cone pigments (protanomalous or deuteranomalous trichromats) or the absence of one of the pigments (protanopia or deuteranopia), the most frequent. Absence of two of the pigments (blue cone monochromacy) is very rare and differs from achromatopsia. The physiological basis of the main tests for easy clinical screening are presented. Testing methods designed for children are reviewed. The Ishihara test is the most widely used screening test specific for congenital color defects. If the plates are correctly read, the child has normal color vision. If not, arrangement tests such as Panel D 15 and desaturated Panel D 15 tests can be used to diagnose the type of the defect (protan or deutan) and grade the degree of color deficiency according to a strategy adapted to children. Examples of results are presented for each axis along which caps are confused, providing a quick and easy preliminary diagnosis. Early detection of color vision malfunction in children allows parents and teachers to make necessary adjustments to the teaching methods for appropriate learning.

A quarter of a century ago, the first systematic behavioral experiments were performed to clarify the nature of color constancy—the effect whereby the perceived color of a surface remains constant despite changes in the spectrum of the illumination. At about the same time, new models of color constancy appeared, along with physiological data on cortical mechanisms and photographic colorimetric measurements of natural scenes. Since then, as this review shows, there have been many advances. The theoretical requirements for constancy have been better delineated and the range of experimental techniques has been greatly expanded; novel invariant properties of images and a variety of neural mechanisms have been identified; and increasing recognition has been given to the relevance of natural surfaces and scenes as laboratory stimuli. Even so, there remain many theoretical and experimental challenges, not least to develop an account of color constancy that goes beyond deterministic and relatively simple laboratory stimuli and instead deals with the intrinsically variable nature of surfaces and illuminations present in the natural world.

Light is used to illuminate objects in the built environment. Humans can only observe light reflected from an object. Light absorbed by an object turns into heat and does not contribute to visibility. Since the spectral output of the new lighting technologies can be tuned, it is possible to imagine a lighting system that detects the colours of objects and emits customised light to minimise the absorbed energy. Previous optimisation studies investigated the use of narrowband LEDs to maximise the efficiency and colour quality of a light source. While these studies aimed to tune a white light source for general use, the lighting system proposed here minimises the energy consumed by lighting by detecting colours of objects and emitting customised light onto each coloured part of the object. This thesis investigates the feasibility of absorption-minimising light source spectra and their impact on the colour appearance of objects and energy consumption. Two computational studies were undertaken to form the theoretical basis of the absorption-minimising light source spectra. Computational simulations show that the theoretical single-peak spectra can lower the energy consumption up to around 38 % to 62 %, and double-peak test spectra can result in energy savings up to 71 %, without causing colour shifts. In these studies, standard reference illuminants, theoretical test spectra and coloured test samples were used. These studies are followed by the empirical evidence collected from two psychophysical experiments. Data from the experiments show that observers find the colour appearance of objects equally natural and attractive under spectrally optimised spectra and reference white light sources. An increased colour difference, to a certain extent, is found acceptable, which allows even higher energy savings. However, the translucent nature of some objects may negatively affect the results.

The better quality pdf is downloadible from here: "http://www.leoalmanac.org/wp-content/uploads/2013/07/LEAVol19No3-Mailman.pdf
Through recent artistic practices and technology of interactive systems for music, composition and improvisation have more and more blended and interconnected with each other – a sui generis situation now called comprovisation. The concept of comprovisation applies equally well to the spontaneous generation and manipulation of computer graphics, especially as such graphics are systematically coordinated audio-visually, while being subject to spontaneous manipulation by a performer.
This is explained in terms of the Fluxations and FluxNoisations Human Body Interfaces, interactive dance systems that generate music and graphics spontaneously in response to hand and body movement. They enable spontaneous expressive shaping of coherent complexity and variety. Thus a multi-layered multimodal experience arises. The aesthetic experience of this multimedia spectacle relates to experiences of various prior music and visual art of the 19th, 20th, and 21st centuries, as well as to hypothetical physical realities. Thus a kind of cybernetic phenomenology of art is pursued and enacted through an embodied cybersynthesis of art with simulated alternate reality. Call it a pragmatic speculative realism, an adventurous technoetic ‘what if.’ As compared to more traditional forms of improvisation, the opportunities for risk-taking and aesthetic exploration rise to a new level of uncertainty, as the reactions of the improviser simultaneously draw from and target both visual and aural modalities, such that the intentions toward each fuse together."

In this study human color constancy was tested for two-dimensional (2D) and three-dimensional (3D) setups with real objects and lights. Four different illuminant changes, a natural selection task and a wide choice of target colors were used. We found that color constancy was better when the target color was learned as a 3D object in a cue-rich 3D scene than in a 2D setup. This improvement was independent of the target color and the illuminant change. We were not able to find any evidence that frequently experienced illuminant changes are better compensated for than unusual ones. Normalizing individual color constancy hit rates by the corresponding color memory hit rates yields a color constancy index, which is indicative of observers' true ability to compensate for illuminant changes.